Publications by authors named "Per Aagaard"

167 Publications

Lack of increased rate of force development after strength training is explained by specific neural, not muscular, motor unit adaptations.

J Appl Physiol (1985) 2021 Nov 18. Epub 2021 Nov 18.

Department of Bioengineering, Imperial College London, London, United Kingdom.

While maximal force increases following short-term isometric strength training, the rate of force development (RFD) may remain relatively unaffected. The underlying neural and muscular mechanisms during rapid contractions after strength training are largely unknown. Since strength training increases the neural drive to muscles, it may be hypothesized that there are distinct neural or muscular adaptations determining the change in RFD independently of an increase in maximal force. Therefore, we examined motor unit population data acquired from surface electromyography during the rapid generation of force before and after four weeks of strength training. We observed that strength training did not change the RFD because it did not influence the number of motor units recruited per second or their initial discharge rate during rapid contractions. While strength training did not change motoneuron behaviour in the force increase phase of rapid contractions, it increased the discharge rate of motoneurons (by ~4 spikes/s) when reaching the plateau phase (~150 ms) of the rapid contractions, determining an increase in maximal force production. Computer simulations with a motor unit model that included neural and muscular properties, closely matched the experimental observations and demonstrated that the lack of change in RFD following training is primarily mediated by an unchanged maximal recruitment speed of motoneurons. These results demonstrate that maximal force and contraction speed are determined by different adaptations in motoneuron behaviour following strength training and indicate that increases in the recruitment speed of motoneurons are required to evoke training-induced increases in RFD.
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http://dx.doi.org/10.1152/japplphysiol.00218.2021DOI Listing
November 2021

Effects of Whole-Season Training and Match-Play on Hip Adductor and Abductor Muscle Strength in Soccer Players: A Pilot Study.

Sports Health 2021 Nov 10:19417381211053783. Epub 2021 Nov 10.

Centre for Sport Studies, Rey Juan Carlos University, Fuenlabrada, Spain.

Background: Previous investigations have associated weakness of hip muscles with a higher likelihood of developing hip groin injury. However, no previous investigation has examined the influence of soccer training and match-play during the season on maximal isometric hip adductor and abductor muscle strength.

Hypothesis: Maximal hip adductor and abductor muscle strength would increase after the preseason, maintaining relatively constant levels across the soccer season.

Design: Cross-sectional study.

Level Of Evidence: Level 3.

Methods: A total of 26 semiprofessional male soccer players underwent measurements of maximal isometric hip adductor and abductor muscle strength at 3 time points of the soccer season: preseason, midseason, and end-season to investigate the longitudinal effect of soccer training and competition during a complete season on maximal isometric hip adductor and abductor muscle strength in the semiprofessional Spanish soccer player.

Results: Compared with preseason, hip abductor muscle strength increased in the midseason (14.2% and 17.1%, for dominant and nondominant limb, respectively; < 0.001) and in the end-season (13.1%; = 0.005, and 14.1%; < 0.005). In contrast, hip adductor muscle strength remained unchanged across the season in both limbs. As a result, the adductor/abductor strength ratio in the nondominant limb was reduced at midseason and end-season time points (-14.6% and -18.4%, respectively; < 0.001) with a corresponding tendency in the dominant limb (-9.3% and -15.0%, respectively; > 0.05).

Conclusion: While maximal hip abductor muscle strength increased throughout the season, hip adductor muscle strength remained stable across the season. This produced a substantial deficit in hip adductor/abductor strength ratio at midseason and end-season.

Clinical Relevance: The progressive imbalance in adductor/abductor strength across the soccer season may be an indicator of increased risk of groin injury and may reinforce the need for preventive rehabilitation activities focused on enhancing adductor muscle strength.
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http://dx.doi.org/10.1177/19417381211053783DOI Listing
November 2021

Effects of blood-flow restricted resistance training on mechanical muscle function and thigh lean mass in sIBM patients.

Scand J Med Sci Sports 2021 Oct 12. Epub 2021 Oct 12.

Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.

Sporadic inclusion body myositis (sIBM) is an idiopathic inflammatory muscle disease associated with skeletal muscle inflammation and a parallel progressive decline in muscle strength and physical function. Eventually, most sIBM patients require use of wheelchair after about 10 years of diagnosis and assistance to perform activities of daily living. This study presents data from a randomized controlled intervention trial (NCT02317094) that examined the effect of 12 weeks low-load blood-flow restricted (BFR) resistance training on maximal muscle strength, power, rate of force development (RFD), thigh lean mass (TLM), and voluntary muscle activation (VA) in sIBM patients. A time-by-group interaction in knee extensor strength was observed in the stronger leg (p ≤ 0.033) but not the weaker leg. Within-group changes were observed with BFR training (BFR) manifested by increased knee extensor strength in the strongest leg (+13.7%, p = 0.049), whereas non-exercising patients (CON) showed reduced knee extensor strength (-7.7%, p = 0.018). Maximal leg extensor power obtained for the stronger leg remained unchanged following BFR training (+9.5%, p = 0.37) while decreasing in CON (-11.1%, p = 0.05). No changes in TLM were observed. VA declined post-training (p = 0.037) in both BFR (-6.3% points) and CON (-7.5% points). The present data indicate that BFR resistance training can attenuate the rate of decline in mechanical muscle function typically experienced by sIBM patients. The preservation of muscle mass and mechanical muscle function with BFR resistance training may be considered of high clinical importance in sIBM patients to countermeasure the disease-related decline in physical function.
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http://dx.doi.org/10.1111/sms.14079DOI Listing
October 2021

Changes in systemic GDF15 across the adult lifespan and their impact on maximal muscle power: the Copenhagen Sarcopenia Study.

J Cachexia Sarcopenia Muscle 2021 Oct 6. Epub 2021 Oct 6.

CopenAge - Copenhagen Center for Clinical Age Research, University of Copenhagen, Copenhagen, Denmark.

Background: Although growth differentiation factor 15 (GDF15) is known to increase with disease and is associated with low physical performance, the role of GDF15 in normal ageing is still not fully understood. Specifically, the influence of circulating GDF15 on impairments in maximal muscle power (a major contributor to functional limitations) and the underlying components has not been investigated.

Methods: Data from 1305 healthy women and men aged 20 to 93 years from The Copenhagen Sarcopenia Study were analysed. Circulating levels of GDF15 and markers of inflammation (tumor necrosis factor-alpha, interleukin-6, and high-sensitivity C-reactive protein) were measured by ELISA (R&D Systems) and multiplex bead-based immunoassays (Bio-Rad). Relative (normalized to body mass), allometric (normalized to height squared), and specific (normalized to leg muscle mass) muscle power were assessed by the Nottingham power rig [leg extension power (LEP)] and the 30 s sit-to-stand (STS) muscle power test. Total body fat, visceral fat, and leg lean mass were assessed by dual energy X-ray absorptiometry. Leg skeletal muscle index was measured as leg lean mass normalized to body height squared.

Results: Systemic levels of GDF15 increased progressively as a function of age in women (1.1 ± 0.4 pg·mL ·year ) and men (3.3 ± 0.6 pg·mL ·year ) (both P < 0.05). Notably, GDF15 increased at a faster rate from the age of 65 years in women (11.5 ± 1.2 pg·mL ·year , P < 0.05) and 70 years in men (19.3 ± 2.3 pg·mL ·year , P < 0.05), resulting in higher GDF15 levels in men compared with women above the age of 65 years (P < 0.05). Independently of age and circulatory markers of inflammation, GDF15 was negatively correlated to relative STS power (P < 0.05) but not LEP, in both women and men. These findings were mainly explained by negative associations of GDF15 with specific STS power in women and men (both P < 0.05).

Conclusions: A J-shaped relationship between age and systemic GDF15 was observed, with men at older age showing steeper increases and elevated GDF15 levels compared with women. Importantly, circulating GDF15 was independently and negatively associated with relative STS power, supporting the potential role of GDF15 as a sensitive biomarker of frailty in older people.
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http://dx.doi.org/10.1002/jcsm.12823DOI Listing
October 2021

Effects of repetitive transcranial magnetic stimulation on recovery in lower limb muscle strength and gait function following spinal cord injury: a randomized controlled trial.

Spinal Cord 2021 Sep 9. Epub 2021 Sep 9.

Spinal Cord Injury Center of Western Denmark, Regional Hospital Viborg, Viborg, Denmark.

Study Design: Randomized sham-controlled clinical trial.

Objectives: The objective of this study is to investigate the effects of repetitive transcranial magnetic stimulation (rTMS) compared to sham stimulation, on the development of lower limb muscle strength and gait function during rehabilitation of spinal cord injury (SCI).

Setting: SCI rehabilitation hospital in Viborg, Denmark.

Methods: Twenty individuals with SCI were randomized to receive rTMS (REAL, n = 11) or sham stimulation (SHAM, n = 9) and usual care for 4 weeks. rTMS (20 Hz, 1800 pulses per session) or sham stimulation was delivered over leg M1 Monday-Friday before lower limb resistance training or physical therapy. Lower limb maximal muscle strength (MVC) and gait function were assessed pre- and post intervention. Lower extremity motor score (LEMS) was assessed at admission and at discharge.

Results: One individual dropped out due to seizure. More prominent increases in total leg (effect size (ES): 0.40), knee flexor (ES: 0.29), and knee extensor MVC (ES: 0.34) were observed in REAL compared to SHAM; however, repeated-measures ANOVA revealed no clear main effects for any outcome measure (treatment p > 0.15, treatment × time p > 0.76, time p > 0.23). LEMS improved significantly for REAL at discharge, but not for SHAM, and REAL demonstrated greater improvement in LEMS than SHAM (p < 0.02). Similar improvements in gait performance were observed between groups.

Conclusions: High-frequency rTMS may increase long-term training-induced recovery of lower limb muscle strength following SCI. The effect on short-term recovery is unclear. Four weeks of rTMS, when delivered in conjunction with resistance training, has no effect on recovery of gait function, indicating a task-specific training effect.
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http://dx.doi.org/10.1038/s41393-021-00703-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8428490PMC
September 2021

High-intensity strength training in patients with idiopathic inflammatory myopathies: a randomised controlled trial protocol.

BMJ Open 2021 06 25;11(6):e043793. Epub 2021 Jun 25.

Rigshospitalet, Copenhagen University Hospital Center for Rheumatology and Spine Diseases, Copenhagen, Denmark.

Introduction: Idiopathic inflammatory myopathies (IIMs) are rare diseases characterised by non-suppurative inflammation of skeletal muscles and muscle weakness. Additionally, IIM is associated with a reduced quality of life. Strength training is known to promote muscle hypertrophy and increase muscle strength and physical performance in healthy young and old adults. In contrast, only a few studies have examined the effects of high intensity strength training in patients with IIM and none using a randomised controlled trial (RCT) set-up. Thus, the purpose of this study is to investigate the effects of high-intensity strength training in patients affected by the IIM subsets polymyositis (PM), dermatomyositis (DM) and immune-mediated necrotising myopathy (IMNM) using an RCT study design.

Methods And Analysis: 60 patients with PM, DM or IMNM will be included and randomised into (1) high-intensity strength training or (2) Care-as-Usual. The intervention period is 16 weeks comprising two whole-body strength exercise sessions per week. The primary outcome parameter will be the changes from pre training to post training in the Physical Component Summary measure in the Short Form-36 health questionnaire. Secondary outcome measures will include maximal lower limb muscle strength, skeletal muscle mass, functional capacity, disease status (International Myositis Assessment and Clinical Studies Group core set measures) and questionnaires assessing physical activity levels and cardiovascular comorbidities. Furthermore, blood samples and muscle biopsies will be collected for subsequent analyses.

Ethics And Dissemination: The study complies with the Helsinki Declaration II and is approved by The Danish Data Protection Agency (P-2020-553). The study is approved by The Danish National Committee on Health Research Ethics (H-20030409). The findings of this trial will be submitted to relevant peer-reviewed journals. Abstracts will be submitted to international conferences.

Trial Registration Number: NCT04486261.
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http://dx.doi.org/10.1136/bmjopen-2020-043793DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8237738PMC
June 2021

Medio-Lateral Hamstring Muscle Activity in Unilateral vs. Bilateral Strength Exercises in Female Team Handball Players - A Cross-Sectional Study.

Int J Sports Phys Ther 2021 Jun 1;16(3):704-714. Epub 2021 Jun 1.

Human Movement Analysis Laboratory, Dept. of Orthopaedic Surgery, Copenhagen University Hospital Amager-Hvidovre, Hvidovre, Denmark.

Background: Reduced activation of the hamstring muscles and specifically the medial semitendinosus muscle (ST) has been shown to be a risk factor for non-contact anterior cruciate ligament (ACL) injury. Specific hamstring strength exercises may show high ST activity, however the effect of unilateral vs. bilateral exercise execution on ST activation remains unknown.

Purpose: To investigate selected lower limb strengthening exercises performed either unilaterally or bilaterally to identify 1) which exercise elicited the highest hamstring activation, 2) which exercise elicited the highest ST activation, and 3) to examine if unilateral exercise execution altered the medio-lateral hamstring activation pattern. Furthermore, the kinematic characteristics of each specific exercise and execution modality were determined to reveal possible causes for differences in medio-lateral hamstring activation between the different exercise conditions.

Study Design: Cross-sectional study.

Methods: Single-session repeated measures were obtained in a randomized manner. Twenty-three female elite team handball players were recruited. Hamstring electromyographic (EMG) activity and 3D kinematics were obtained during selected lower limb exercises (hip thrust, kettlebell swing, Romanian deadlift). Hamstring EMG activity, normalized to maximal voluntary contraction (MVC) (nEMG), and inter-muscular activation difference between the ST and lateral hamstring biceps femoris (BF) were compared across exercises using two-way repeated measures ANOVA.

Results: Bilateral hip thrust demonstrated highest overall hamstring activity (68.9±16.6 %). Kettlebell swing (Δ13%-point, p<0.01) and Romanian deadlift (Δ20-24%-point, p<0.01) demonstrated greater ST-BF activation differences (Δ=ST-BF) in favor of ST compared to hip thrust (Δ2-7%). Positive correlations were observed between knee joint angle and ST activity in kettlebell swing and deadlift.

Conclusion: Kettlebell swing, deadlift and hip thrust all produced high activation of the hamstring muscles. Kettlebell swing and both deadlift exercises were superior in activating ST over BF, favoring these exercises in the prevention of non-contact ACL injury in female athletes, which should be evaluated in future intervention studies.

Level Of Evidence: 3.
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http://dx.doi.org/10.26603/001c.24150DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8168984PMC
June 2021

Assessment of functional sit-to-stand muscle power: Cross-sectional trajectories across the lifespan.

Exp Gerontol 2021 09 9;152:111448. Epub 2021 Jun 9.

Geriatric Research Unit, Geriatric Department, Bispebjerg University Hospital, Copenhagen, Denmark; Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet-Glostrup University Hospital, Copenhagen, Denmark; Geriatric Research Unit, Department of Internal Medicine, Herlev-Gentofte University Hospital, Copenhagen, Denmark. Electronic address:

Background: The 30-s sit-to-stand (STS) muscle power test is a valid test to assess muscle power in older people; however, whether it may be used to assess trajectories of lower-limb muscle power through the adult lifespan is not known. This study evaluated the pattern and time course of variations in relative, allometric and specific STS muscle power throughout the lifespan.

Methods: Subjects participating in the Copenhagen Sarcopenia Study (729 women and 576 men; aged 20 to 93 years) were included. Lower-limb muscle power was assessed with the 30-s version of the STS muscle power test. Allometric, relative and specific STS power were calculated as absolute STS power normalized to height squared, body mass and leg lean mass as assessed by DXA, respectively.

Results: Relative STS muscle power tended to increase in women (0.08 ± 0.05 W·kg·yr; p = 0.082) and increased in men (0.14 ± 0.07 W·kg·yr; p = 0.046) between 20 and 30 years, followed by a slow decline (-0.05 ± 0.05 W·kg·yr and -0.06 ± 0.08 W·kg·yr, respectively; both p > 0.05) between 30 and 50 years. Then, relative STS power declined at an accelerated rate up to oldest age in men (-0.09 ± 0.02 W·kg·yr) and in women until the age of 75 (-0.09 ± 0.01 W·kg·yr) (both p < 0.001). A lower rate of decline was observed in women aged 75 and older (-0.04 ± 0.02 W·kg·yr; p = 0.039). Similar age-related patterns were noted for allometric and specific STS power.

Conclusions: The STS muscle power test appears to provide a feasible and inexpensive tool to monitor cross-sectional trajectories of muscle power throughout the lifespan.
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http://dx.doi.org/10.1016/j.exger.2021.111448DOI Listing
September 2021

Force-velocity-power profiling of maximal effort sprinting, jumping and hip thrusting: Exploring the importance of force orientation specificity for assessing neuromuscular function.

J Sports Sci 2021 Sep 6;39(18):2115-2122. Epub 2021 May 6.

Institute for Nutrition, Exercise and Sports, Department of Integrative Physiology, University of Copenhagen, Copenhagen, Denmark.

Comprehensive information regarding neuromuscular function, as assessed through force-velocity-power (FVP) profiling, is of importance for training optimization in athletes. However, neuromuscular function is highly task-specific, potentially governed by dissimilarity of the overall orientation of forceapplication. The hip thrust (HT) exercise is thought to be of relevance for sprinting considering its antero-posterior force orientation and considerable hip-extensor recruitment, however, the association between their respective FVP profiles remains unexplored. Therefore, to address the concept of force orientation specificity within FVP profiling, the maximal theoretical neuromuscular capabilities of 41 professional male footballers (22.1 ± 4.1 years, 181.8 ± 6.4 cm, 76.4 ± 5.5 kg) were assessed during sprint acceleration, squat jumping (SJ) and the HT exercise. No significant associations were observed for maximal theoretical force or velocity between the three FVP profiling modalities, however, maximal theoretical power (Pmax) was correlated between sprinting and SJ (r = 0.73, P < 0.001) and HT and SJ (r = 0.44, P = 0.01), but not between sprinting and HT (r = 0.18, P = 0.36). In conclusion, although Pmax may be considered a somewhat universal lower-extremity capability, neuromuscular function is associated with substantial task-specificity not solely governed by the overall direction of force orientation.
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http://dx.doi.org/10.1080/02640414.2021.1920128DOI Listing
September 2021

Exercise-induced fluid shifts are distinct to exercise mode and intensity: a comparison of blood flow-restricted and free-flow resistance exercise.

J Appl Physiol (1985) 2021 06 29;130(6):1822-1835. Epub 2021 Apr 29.

Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.

MRI can provide fundamental tools in decoding physiological stressors stimulated by training paradigms. Acute physiological changes induced by three diverse exercise protocols known to elicit similar levels of muscle hypertrophy were evaluated using muscle functional magnetic resonance imaging (mfMRI). The study was a cross-over study with participants ( = 10) performing three acute unilateral knee extensor exercise protocols to failure and a work matched control exercise protocol. Participants were scanned after each exercise protocol; 70% 1 repetition maximum (RM) (FF70); 20% 1RM (FF20); 20% 1RM with blood flow restriction (BFR20); free-flow (FF) control work matched to BFR20 (FF20). Post exercise mfMRI scans were used to obtain interleaved measures of muscle R2 (indicator of edema), R2' (indicator of deoxyhemoglobin), muscle cross sectional area (CSA) blood flow, and diffusion. Both BFR20 and FF20 exercise resulted in a larger acute decrease in R2, decrease in R2', and expansion of the extracellular compartment with slower rates of recovery. BFR20 caused greater acute increases in muscle CSA than FF20 and FF70. Only BFR20 caused acute increases in intracellular volume. Postexercise muscle blood flow was higher after FF70 and FF20 exercise than BFR20. Acute changes in mean diffusivity were similar across all exercise protocols. This study was able to differentiate the acute physiological responses between anabolic exercise protocols. Low-load exercise protocols, known to have relatively higher energy contributions from glycolysis at task failure, elicited a higher mfMRI response. Noninvasive mfMRI represents a promising tool for decoding mechanisms of anabolic adaptation in muscle. Using muscle functional MRI (mfMRI), this study was able to differentiate the acute physiological responses following three established hypertrophic resistance exercise strategies. Low-load exercise protocols performed to failure, with or without blood flow restriction, resulted in larger changes in R (i.e. greater T-shifts) with a slow rate of return to baseline indicative of myocellular fluid shifts. These data were cross evaluated with interleaved measures of macrovascular blood flow, water diffusion, muscle cross sectional area (i.e. acute macroscopic muscle swelling), and intracellular water fraction measured using MRI.
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http://dx.doi.org/10.1152/japplphysiol.01012.2020DOI Listing
June 2021

Hamstring and Quadriceps Muscle Strength in Youth to Senior Elite Soccer: A Cross-Sectional Study Including 125 Players.

Int J Sports Physiol Perform 2021 Apr 22:1-7. Epub 2021 Apr 22.

Purpose: Increasing age, high quadriceps strength, and low hamstring muscle strength are associated with hamstring strain injury in soccer. The authors investigated the age-related variation in maximal hamstring and quadriceps strength in male elite soccer players from under-13 (U-13) to the senior level.

Methods: A total of 125 elite soccer players were included from a Danish professional soccer club and associated youth academy (first tier; U-13, n = 19; U-14, n = 16; U-15, n = 19; U-17, n = 24; U-19, n = 17; and senior, n = 30). Maximal voluntary isometric force was assessed for the hamstrings at 15° knee joint angle and for the quadriceps at 60° knee joint angle (0° = full extension) using an external-fixated handheld dynamometer. Hamstring-to-quadriceps strength (H:Q) ratio and hamstring and quadriceps maximal voluntary isometric force levels were compared across age groups (U-13 to senior).

Results: Senior players showed 18% to 26% lower H:Q ratio compared with all younger age groups (P ≤ .026). Specific H:Q ratios (mean [95% confidence interval]) were as follows: senior, 0.45 (0.42-0.48); U-19, 0.61 (0.55-0.66); U-17, 0.56 (0.51-0.60); U-15, 0.59 (0.54-0.64); U-14, 0.54 (0.50-0.59); and U-13, 0.57 (0.51-0.62). Hamstring strength increased from U-13 to U-19 with a significant drop from U-19 to the senior level (P = .048), whereas quadriceps strength increased gradually from U-13 to senior level.

Conclusion: Elite senior soccer players demonstrate lower H:Q ratio compared with youth players, which is driven by lower hamstring strength at the senior level compared with the U-19 level combined with a higher quadriceps strength. This discrepancy in hamstring and quadriceps strength capacity may place senior-level players at increased risk of hamstring muscle strain injuries.
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http://dx.doi.org/10.1123/ijspp.2020-0713DOI Listing
April 2021

The effects of ageing on functional capacity and stretch-shortening cycle muscle power.

J Phys Ther Sci 2021 Mar 17;33(3):250-260. Epub 2021 Mar 17.

Institute of Neuroscience and Physiology, Department of Health and Rehabilitation, Sahlgrenska Academy, University of Gothenburg: Gothenburg, Sweden.

[Purpose] To examine the effects of age and gender in an ageing population with respect to functional decline and the relationship between muscle power and functional capacity. [Participants and Methods] The cohort (N=154) was subdivided into youngest-old (65-70 years.; n=62), middle-old (71-75 years.; n=46), and oldest-old (76-81 years.; n=46). Measures of mechanical muscle function included countermovement jump height, muscle power, leg strength and grip strength. Functional performance-based measures included heel-rise, postural balance, Timed Up and Go, and gait speed. [Results] The oldest-old performed significantly worse than the middle-old, whereas the youngest-old did not outperform the middle-old to the same extent. Increased contribution of muscle power was observed with increasing age. Males had consistently higher scores in measures of mechanical muscle function, whereas no gender differences were observed for functional capacity. [Conclusion] The age-related decline in functional capacity appears to accelerate when approaching 80 years of age and lower limb muscle power seems to contribute to a greater extent to the preservation of functional balance and gait capacity at that stage. Males outperform females in measures of mechanical muscle function independent of age, while the findings give no support for the existence of gender differences in functional capacity.
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http://dx.doi.org/10.1589/jpts.33.250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8012187PMC
March 2021

Effects of high-intensity interval training combined with traditional strength or power training on functionality and physical fitness in healthy older men: A randomized controlled trial.

Exp Gerontol 2021 07 20;149:111321. Epub 2021 Mar 20.

Exercise Research Laboratory, School of Physical Education, Physiotherapy and Dance, Universidade Federal do Rio Grande do Sul, Brazil. Electronic address:

Concurrent training (CT) is an efficient strategy to improve neuromuscular function and cardiorespiratory fitness in older adults, which are factors of pivotal importance for the maintenance of functional capacity with aging. However, there is a lack of evidence about the effectiveness of power training (PT) as an alternative to traditional strength training (TST) during CT. Thus, the aim of the present study was to examine the effect of 16 weeks (twice weekly) TST combined with high intensity interval training (TST + HIIT) vs. PT combined with HIIT (PT + HIIT) on functional performance, cardiorespiratory fitness and body composition in older men. Thirty five older men (65.8 ± 3.9 years) were randomly allocated into two training groups: TST + HIIT (n = 18), and PT + HIIT (n = 17). TST + HIIT performed resistance training at intensities ranging from 65% to 80% 1RM at slow controlled speed (≅ 2 s for each concentric phase), whereas PT + HIIT trained at intensities ranging from 40% to 60% of 1RM at maximal intentional speed. Both groups performed HIIT at intensities ranging from 75 to 90% of VO. Participants performed functional tests (sit-to-stand, timed-up-and-go, stair climbing); cardiopulmonary exercise testing (maximal cycling power output: W, peak oxygen uptake: VO, cycling economy), as well as body composition assessment (DXA) before, post 8 and post 16 weeks of training. The groups improved similarly (P < 0.05) with training in all functional capacity outcomes, W, cycling economy, VO and body composition (P < 0.05). These findings suggest that HIIT based CT programs involving TST vs. PT are equally effective in improving functionality, cardiorespiratory fitness and body composition in healthy older men.
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http://dx.doi.org/10.1016/j.exger.2021.111321DOI Listing
July 2021

Low-intensity resistance exercise with blood flow restriction and arterial stiffness in humans: A systematic review.

Scand J Med Sci Sports 2021 Mar 22;31(3):498-509. Epub 2020 Dec 22.

Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.

Low-intensity resistance exercise with blood flow restriction exercise is an emerging type of exercise recognition worldwide. This systematic review evaluated the effects of low-intensity resistance exercise performed with concurrent blood flow restriction (LIRE-BFR) on acute and chronic measures of arterial stiffness in humans. A systematic search in six healthcare science databases and reference lists was conducted. Data selected for primary analysis consisted of post-intervention changes in arterial stiffness markers. This systematic review included randomized and non-randomized controlled trials of LIRE-BFR in humans. 156 articles were initially identified, 15 of which met inclusion criteria. Ten studies were excluded because they did not match predefined arterial stiffness markers. Thus, five articles were included in this review: two acute studies (N = 39 individuals, age = 20-30 years old, 30.8% women and 69.2% men) and three longitudinal studies (N = 51 individuals, age = 24-86-years old, 41.2% women and 58.8% men). Acute LIRE-BFR demonstrated both positive and negative effects on arterial stiffness in healthy young people. In contrast, longitudinal studies reported neutral effects in healthy young and older people. In conclusion, LIRE-BFR applied to the upper and lower limbs may acutely induce increases in central blood pressure and pulse wave velocity in healthy young people, whereas LIRE-BFR for the lower limbs may elicit positive effects related to indirect markers of arterial stiffness. Moreover, longitudinal LIRE-BFR studies showed no changes in arterial stiffness in young and older people. Hence, LIRE-BFR should be prescribed with a degree of caution to avoid non-intended responses in arterial stiffness markers in humans.
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http://dx.doi.org/10.1111/sms.13902DOI Listing
March 2021

Effects of small-sided recreational team handball training on mechanical muscle function, body composition and bone mineralization in untrained young adults-A randomized controlled trial.

PLoS One 2020 18;15(11):e0241359. Epub 2020 Nov 18.

Department of Sports Science and Clinical Biomechanics, Muscle Physiology and Biomechanics, University of Southern Denmark, Odense, Denmark.

Prolonged physical inactivity in young adults may lead to deficiencies in musculoskeletal fitness, and thus a need exists to develop physical activity and exercise programmes that are effective of increasing musculoskeletal fitness. The aim of this study, therefore, was to investigate the effects of small-sided team handball training on lower limb muscle strength, postural balance and body composition in young adults. Twenty-six men and twenty-eight women were stratified for peak oxygen uptake (VO2peak) and body fat percentage and randomly allocated to either 12 wks of small-sided recreational team handball training (THG: 14 men and 14 women, age 24.1±2.6 yrs (mean±SD), VO2peak 39.8±5.9 ml/kg/min and body fat percentage 32.7±8.7%) or serving as non-exercising controls (CON: 12 men and 14 women, age 24.8±3.1 yrs, VO2peak 39.7±5.0 ml/kg/min, body fat percentage 31.7±9.7%). THG trained on average 1.8 times/week for 12 wks. At 0 and 12 wks, lower limb muscle strength, rate of force development (RFD), vertical jump height and power, postural balance, body composition and muscle biopsies were assessed. No training effects were observed for maximal isokinetic or isometric knee extensor strength, maximal vertical jump height or take-off power, fibre type distribution or capillarization. Late phase (RFD) increased (+7.4%, p<0.05) and postural sway excursion length was improved after training (-9%, p<0.05) in THG with no difference from CON (p>0.05). Further, THG demonstrated a decrease in body fat percentage (-3.7%) accompanied by increases in whole-body fat free mass (FFM) (+2.2%), leg FFM (+2.5%), total bone mineral content (BMC) (+1.1%), leg BMC (+1.2%), total hip bone mineral density (+1.6%) and hip T-score (+50%) which differed from CON (all p<0.05). In conclusion, recreational small-sided team handball training appears to effectively improve rapid force capacity, postural balance, lean and fat body mass and bone health in previously untrained young adults. The study was registered at ClinicalTrials.gov (NCT04247724). ClinicalTrials.gov ID number: NCT04247724.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0241359PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7673568PMC
December 2020

Rate of Force Development Remains Reduced in the Knee Flexors 3 to 9 Months After Anterior Cruciate Ligament Reconstruction Using Medial Hamstring Autografts: A Cross-Sectional Study.

Am J Sports Med 2020 11 20;48(13):3214-3223. Epub 2020 Oct 20.

Department of Sports Science and Clinical Biomechanics, Muscle Physiology and Biomechanics Research Unit, University of Southern Denmark, Odense, Denmark.

Background: Anterior cruciate ligament (ACL) rupture is a serious injury with a high prevalence worldwide, and subsequent ACL reconstructions (ACLR) appear to be most commonly performed using hamstring-derived (semitendinosus tendon) autografts. Recovery of maximal muscle strength to ≥90% of the healthy contralateral limb is considered an important criterion for safe return to sports. However, the speed of developing muscular force (ie, the rate of force development [RFD]) is also important for the performance of many types of activities in sports and daily living, yet RFD of the knee extensor and flexor muscles has apparently never been examined in patients who undergo ACLR with hamstring autograft (HA).

Purpose: To examine potential deficits in RFD, maximal muscle strength (ie, maximal voluntary isometric contraction [MVIC]), and functional capacity of ACLR-HA limbs in comparison with the healthy contralateral leg and matched healthy controls 3 to 9 months after surgery.

Study Design: Cross-sectional study; Level of evidence: 3.

Methods: A total of 23 young patients who had undergone ACLR-HA 3 to 9 months earlier were matched by age to 14 healthy controls; both groups underwent neuromuscular screening. Knee extensor and flexor MVIC and RFD, as well as functional capacity (single-leg hop for distance [SLHD] test, timed single-leg sit-to-stand [STS] test), were assessed on both limbs. Furthermore, patient-reported knee function (Knee injury and Osteoarthritis Outcome Score) was assessed.

Results: Knee extensor and flexor MVIC and RFD were markedly compromised in ACLR-HA limbs compared with healthy contralateral limbs (MVIC for extensor and flexor, 13% and 26%, respectively; RFD, 14%-17% and 32%-39%) and controls (MVIC, 16% and 31%; RFD, 14%-19% and 30%-41%) ( < .05-.001). Further, ACLR-HA limbs showed reduced functional capacity (reduced SLHD and STS performance) compared with contralateral limbs (SLHD, 11%; STS, 14%) and controls (SLHD, 20%; STS, 31%) ( < .01-.001). Strength (MVIC) and functional (SLHD) parameters were positively related to the duration of time after surgery ( < .05), although this relationship was not observed for RFD and STS.

Conclusion: Knee extensor and flexor RFD and maximal strength, as well as functional single-leg performance, remained substantially reduced in ACLR-HA limbs compared with noninjured contralateral limbs and healthy controls 3 to 9 months after reconstructive surgery.
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http://dx.doi.org/10.1177/0363546520960108DOI Listing
November 2020

[Blood-flow restricted walking exercise as rehabilitation for a patient with chronic knee osteoarthritis].

Ugeskr Laeger 2020 10;182(41)

In this case report, a 75-year-old woman with symptomatic knee osteoarthritis completed nine weeks (27 sessions, nine supervised) of blood-flow restricted (BFR) walking exercise without any discomfort and a 100% training adherence. BFR walking was well tolerated by the patient and resulted in improvements in functional capacity: 30-sec. sit-to-stand, timed up and go, 40-m walk test, and stair climb test. However, no positive changes were noted for maximal knee extensor and knee flexor strength or in Knee Osteoarthritis Outcome Scores.
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October 2020

Relation between leg extension power and 30-s sit-to-stand muscle power in older adults: validation and translation to functional performance.

Sci Rep 2020 10 1;10(1):16337. Epub 2020 Oct 1.

Geriatric Research Unit, Department of Geriatric and Palliative Medicine, Bispebjerg-Frederiksberg University Hospital, Copenhagen, Denmark.

This study aimed to assess the validity and functional relevance of a standardized procedure to assess lower limb muscle power by means of the 30-s sit-to-stand (STS) test when compared to leg extension power (LEP), traditional STS performance and handgrip strength. A total of 628 community-dwelling older subjects (60-93 years) from the Copenhagen Sarcopenia Study were included. Physical performance was assessed by the 30-s STS and 10-m maximal gait speed tests. Handgrip strength and LEP were recorded by a hand-held dynamometer and the Nottingham power rig, respectively. STS muscle power was calculated using the subjects' body mass and height, chair height and the number of repetitions completed in the 30-s STS test. We found a small albeit significant difference between LEP and unilateral STS power in older men (245.5 ± 88.8 vs. 223.4 ± 81.4 W; ES = 0.26; p < 0.05), but not in older women (135.9 ± 51.9 vs. 138.5 ± 49.6 W; ES = 0.05; p > 0.05). Notably, a large positive correlation was observed between both measures (r = 0.75; p < 0.001). Relative STS power was more strongly related with maximal gait speed than handgrip strength, repetition-based STS performance and relative LEP after adjusting for age (r = 0.53 vs 0.35-0.45; p < 0.05). In conclusion, STS power obtained from the 30-s STS test appeared to provide a valid measure of bilateral lower limb power and was more strongly related with physical performance than maximal handgrip strength, repetition-based STS performance and LEP.
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http://dx.doi.org/10.1038/s41598-020-73395-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7529789PMC
October 2020

Efficacy of low-load blood flow restricted resistance EXercise in patients with Knee osteoarthritis scheduled for total knee replacement (EXKnee): protocol for a multicentre randomised controlled trial.

BMJ Open 2020 10 1;10(10):e034376. Epub 2020 Oct 1.

Clinical Medicine, Aarhus University, Aarhus, Denmark.

Introduction: Up to 20% of patients undergoing total knee replacement (TKR) surgery report no or suboptimal pain relief after TKR. Moreover, despite chances of recovering to preoperative functional levels, patients receiving TKR have demonstrated persistent deficits in quadriceps strength and functional performance compared with healthy age-matched adults. We intend to examine if low-load blood flow restricted exercise (BFRE) is an effective preoperative method to increase functional capacity, lower limb muscle strength and self-reported outcomes after TKR. In addition, the study aims to investigate to which extent preoperative BFRE will protect against surgery-related atrophy 3 months after TKR.

Methods: In this multicentre, randomised controlled and assessor blinded trial, 84 patients scheduled for TKR will be randomised to receive usual care and 8 weeks of preoperative BFRE or to follow usual care-only. Data will be collected before randomisation, 3-4 days prior to TKR, 6 weeks, 3 months and 12 months after TKR. Primary outcome will be the change in 30 s chair stand test from baseline to 3-month follow-up. Key secondary outcomes will be timed up and go, 40 me fast-paced walk test, isometric knee extensor and flexor strength, patient-reported outcome and selected myofiber properties.Intention-to-treat principle and per-protocol analyses will be conducted. A one-way analysis of variance model will be used to analyse between group mean changes. Preintervention-to-postintervention comparisons will be analysed using a mixed linear model. Also, paired Student's t-test will be performed to gain insight into the potential pretraining-to-post-training differences within the respective training or control groups and regression analysis will be used for analysation of associations between selected outcomes.

Ethical Approval: The trial has been accepted by the Central Denmark Region Committee on Biomedical Research Ethics (Journal No 10-72-19-19) and the Danish Data Protection Agency (Journal No 652164). All results will be published in international peer-reviewed scientific journals regardless of positive, negative or inconclusive results.

Trial Registration Number: NCT04081493.
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http://dx.doi.org/10.1136/bmjopen-2019-034376DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7534706PMC
October 2020

Subcellular localization- and fibre type-dependent utilization of muscle glycogen during heavy resistance exercise in elite power and Olympic weightlifters.

Acta Physiol (Oxf) 2021 02 4;231(2):e13561. Epub 2020 Oct 4.

Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark.

Aim: Glycogen particles are found in different subcellular localizations, which are utilized heterogeneously in different fibre types during endurance exercise. Although resistance exercise typically involves only a moderate use of mixed muscle glycogen, the hypothesis of the present study was that high-volume heavy-load resistance exercise would mediate a pattern of substantial glycogen depletion in specific subcellular localizations and fibre types.

Methods: 10 male elite weightlifters performed resistance exercise consisting of four sets of five (4 × 5) repetitions at 75% of 1RM back squats, 4 × 5 at 75% of 1RM deadlifts and 4 × 12 at 65% of 1RM rear foot elevated split squats. Muscle biopsies (vastus lateralis) were obtained before and after the exercise session. The volumetric content of intermyofibrillar (between myofibrils), intramyofibrillar (within myofibrils) and subsarcolemmal glycogen was assessed by transmission electron microscopy.

Results: After exercise, biochemically determined muscle glycogen decreased by 38 (31:45)%. Location-specific glycogen analyses revealed in type 1 fibres a large decrement in intermyofibrillar glycogen, but no or only minor changes in intramyofibrillar or subsarcolemmal glycogen. In type 2 fibres, large decrements in glycogen were observed in all subcellular localizations. Notably, a substantial fraction of the type 2 fibres demonstrated near-depleted levels of intramyofibrillar glycogen after the exercise session.

Conclusion: Heavy resistance exercise mediates a substantial utilization of glycogen from all three subcellular localization in type 2 fibres, while mostly taxing intermyofibrillar glycogen stores in type 1 fibres. Thus, a better understanding of the impact of resistance training on myocellular metabolism and performance requires a focus on compartmentalized glycogen utilization.
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http://dx.doi.org/10.1111/apha.13561DOI Listing
February 2021

Feasibility and safety of 4 weeks of blood flow-restricted exercise in an individual with tetraplegia and known autonomic dysreflexia: a case report.

Spinal Cord Ser Cases 2020 09 3;6(1):83. Epub 2020 Sep 3.

Spinal Cord Injury Centre of Western Denmark, Regional Hospital Viborg, Viborg, Denmark.

Introduction: Blood flow-restricted exercise (BFRE) appears to hold considerable potential in spinal cord injury (SCI) rehabilitation, due to its ability to induce beneficial functional changes and morphological alterations from low-intensity, low-load exercise. However, it remains unclear if this training approach is feasible and safe in individuals with autonomic dysreflexia (AD).

Case Presentation: A 23-year-old male with traumatic, cervical (C6), motor-complete (AIS: B) SCI and diagnosed AD completed eight sessions of BFRE for the upper extremities over 4 weeks. Blood pressure and heart rate recordings and perceptual pain responses were collected repeatedly during exercise. Blood samples were drawn pre- and post-training. Training was carried out in a neurorehabilitation hospital setting with appertaining medical staff readiness, and was supervised by a physiotherapist with expertise in AD in general as well as prior knowledge of the present patient's triggers and symptoms. Four incidences of AD (defined as systolic blood pressure increase >20 mmHg) were recorded across all training sessions, of which one was symptomatic. The patient's blood profile did not change considerably from pre- to post-training sessions. Self-reported average pain during training corresponded from "mild" to "moderate".

Discussion: The patient was able to perform 4 weeks of BFRE, but encountered episodes of AD. Similarly, two AD episodes were registered during a single conventional, free-flow resistance training session. Evidence from clinically controlled safety studies is needed in order to establish if and how BFRE can be applied in a rehabilitation strategy in SCI individuals with neurological level of injury at or above T6 level.
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http://dx.doi.org/10.1038/s41394-020-00335-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7471262PMC
September 2020

Physiological responses of human skeletal muscle to acute blood flow restricted exercise assessed by multimodal MRI.

J Appl Physiol (1985) 2020 10 27;129(4):748-759. Epub 2020 Aug 27.

Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.

Important physiological quantities for investigating muscle hypertrophy include blood oxygenation, cell swelling, and changes in blood flow. The purpose of this study was to compare the acute changes of these parameters in human skeletal muscle induced by low-load (20% 1-RM) blood flow-restricted (BFR-20) knee extensor exercise compared with free-flow work-matched (FF-20) and free-flow 50% 1-RM (FF-50) knee extensor exercise using multimodal magnetic resonance imaging (MRI). Subjects ( = 11) completed acute exercise sessions for each exercise mode in an MRI scanner, where interleaved measures of muscle (indicator of edema), [Formula: see text] (indicator of deoxyhemoglobin), macrovascular blood flow, and diffusion were performed before, between sets, and after the final set for each exercise protocol. BFR-20 exercise resulted in larger acute decreases in R and greater increases in cross-sectional area than FF-20 and FF-50 ( < 0.01). Blood oxygenation decreased between sets during BFR-20, as indicated by a 13.6% increase in [Formula: see text] values ( < 0.01)), whereas they remained unchanged for FF-20 and decreased during FF-50 exercise. Quadriceps blood flow between sets was highest for the heavier load (FF-50), averaging 305 mL/min, and lowest for BFR-20 at 123 ± 73 mL/min until post-exercise cuff release, where blood flow rates in BFR-20 exceeded both FF protocols ( < 0.01). Acute changes in diffusion rates were similar for all exercise protocols. This study was able to differentiate the acute exercise response of selected physiological factors associated with skeletal muscle hypertrophy. Marked differences in these parameters were found to exist between BFR and FF exercise conditions, which contribute to explain the anabolic potential of low-load blood flow restricted muscle exercise. Acute changes in blood flow, diffusion, blood oxygenation, cross-sectional area, and the "T shift" are evaluated in human skeletal muscle in response to blood flow-restricted (BFR) and conventional free-flow knee extensor exercise performed in an MRI scanner. The acute physiological response to exercise was dependent on the magnitude of load and the application of BFR. Physiological variables changed markedly and established a steady state rapidly after the first of four exercise sets.
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http://dx.doi.org/10.1152/japplphysiol.00171.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7654733PMC
October 2020

Myocellular Adaptations to Low-Load Blood Flow Restricted Resistance Training.

Exerc Sport Sci Rev 2020 10;48(4):180-187

Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.

Low-load blood flow restricted resistance exercise (BFRRE) can stimulate whole-muscle growth and improve muscle function. However, limited knowledge exists on the effects at the myocellular level. We hypothesize that BFRRE has the ability to produce concurrent skeletal muscle myofibrillar, mitochondrial, and microvascular adaptations, thus offering an alternative strategy to counteract decay in skeletal muscle health and function in clinical populations.
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http://dx.doi.org/10.1249/JES.0000000000000231DOI Listing
October 2020

Assessment of Neuroplasticity With Strength Training.

Exerc Sport Sci Rev 2020 10;48(4):151-162

Department of Nutrition, Exercise and Sports, Section of Integrative Physiology, University of Copenhagen, Copenhagen, Denmark.

Including a brief overview of current investigative approaches, the present Perspectives for Progress article offers an overview of potential future experiments in the field of exercise-related neuroplasticity to strength training. It is proposed that the combination of specific experimental approaches and recently developed techniques holds the potential for unraveling spinal and supraspinal mechanisms involved in the adaptation to strength training.
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http://dx.doi.org/10.1249/JES.0000000000000229DOI Listing
October 2020

Skeletal Muscle Microvascular Changes in Response to Short-Term Blood Flow Restricted Training-Exercise-Induced Adaptations and Signs of Perivascular Stress.

Front Physiol 2020 12;11:556. Epub 2020 Jun 12.

Department of Sports Science and Clinical Biomechanics and SDU Muscle Research Cluster, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark.

Previous reports suggest that low-load muscle exercise performed under blood flow restriction (BFR) may lead to endurance adaptations. However, only few and conflicting results exist on the magnitude and timing of microvascular adaptations, overall indicating a lack of angiogenesis with BFR training. The present study, therefore, aimed to examine the effect of short-term high-frequency BFR training on human skeletal muscle vascularization. Participants completed 3 weeks of high-frequency (one to two daily sessions) training consisting of either BFR exercise [(BFRE) = 10, 22.8 ± 2.3 years; 20% one-repetition maximum (1RM), 100 mmHg] performed to concentric failure or work-matched free-flow exercise [(CON) = 8, 21.9 ± 3.0 years; 20% 1RM]. Muscle biopsies [vastus lateralis (VL)] were obtained at baseline, 8 days into the intervention, and 3 and 10 days after cessation of the intervention to examine capillary and perivascular adaptations, as well as angiogenesis-related protein signaling and gene expression. Capillary per myofiber and capillary area (CA) increased 21-24 and 25-34%, respectively, in response to BFRE ( < 0.05-0.01), while capillary density (CD) remained unchanged. Overall, these adaptations led to a consistent elevation (15-16%) in the capillary-to-muscle area ratio following BFRE ( < 0.05-0.01). In addition, evaluation of perivascular properties indicated thickening of the perivascular basal membrane following BFRE. No or only minor changes were observed in CON. This study is the first to show that short-term high-frequency, low-load BFRE can lead to microvascular adaptations (i.e., capillary neoformation and changes in morphology), which may contribute to the endurance effects previously documented with BFR training. The observation of perivascular membrane thickening suggests that high-frequency BFRE may be associated with significant vascular stress.
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http://dx.doi.org/10.3389/fphys.2020.00556DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303802PMC
June 2020

Contractile rate of force development after anterior cruciate ligament reconstruction-a comprehensive review and meta-analysis.

Scand J Med Sci Sports 2020 Sep 18;30(9):1572-1585. Epub 2020 Jun 18.

Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark.

Study Design: Comprehensive review and meta-analysis.

Background: The recovery in rapid force production measured as the rate of force development (RFD) is not clear after anterior cruciate ligament reconstruction (ACLR).

Objectives: To evaluate (a) time-course change of between-limb asymmetries in isometric knee extension/flexion RFD in individuals post-ACLR and (b) differences in RFD between individuals post-ACLR and healthy controls.

Methods: A literature search of Web of Science, SPORTDiscus, PubMed-MEDLINE, and ScienceDirect identified 10 eligible studies (n = 246) assessing RFD after ACLR.

Results: Standard mean difference (SMD) for early-phase (<100 ms) knee extensor RFD was -1.07 (95% CI: -1.46, -0.68) when comparing ACLR vs uninjured limb, while SMD for late-phase (≥100 ms) RFD was -0.85 (95 CI%: -1.27, -0.42). SMD for early- and late-phase knee flexor RFD was -0.74 (95% CI: -1.19, -0.29) and -0.79 (95% CI: -1.19, -0.39), respectively. Comparing ACLR limbs to uninjured controls, knee extensor SMD for early- and late-phase RFD was -1.42 (95% CI: -2.10, -0.73) and 1.09 (95% CI: -1.81, -0.38). For the knee flexors, SMD for early- and late-phase RFD was -0.78 (95% CI: -1.96, -0.39) and -1.14 (95% CI: -1.60, -0.67).

Conclusions: Anterior cruciate ligament reconstruction limbs demonstrated sustained post-surgical suppression in RFD capacity for the knee extensors/flexors compared to the contralateral limb as well as to healthy controls. Monitoring of RFD should be considered throughout rehabilitation and return to sport (RTS) after ACLR to assess the effectiveness of post-operative rehabilitation. Post-surgical ACLR rehabilitation should include training interventions to enhance RFD.
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http://dx.doi.org/10.1111/sms.13733DOI Listing
September 2020

Adaptations in mechanical muscle function, muscle morphology, and aerobic power to high-intensity endurance training combined with either traditional or power strength training in older adults: a randomized clinical trial.

Eur J Appl Physiol 2020 May 1;120(5):1165-1177. Epub 2020 Apr 1.

Exercise Research Laboratory, School of Physical Education, Physiotherapy and Dance, Universidade Federal do Rio Grande do Sul, Rua Felizardo 750, Bairro Jardim Botânico, Porto Alegre, RS, 90690-200, Brazil.

Purpose: There is a lack of information on the effects of power training (PT) as an alternative to traditional strength training (TST) during concurrent training (CT) in older individuals. This study aimed to verify the neuromuscular adaptations that occurred following 16-week interventions with two CT models in older men: high-intensity interval training (HIIT) combined with either TST or PT.

Methods: Thirty-five older men (65.8 ± 3.9 years) were randomly assigned into one of two training groups CTS: TST + HIIT (n = 18) or CTP: PT + HIIT (n = 17). CTS performed resistance training at intensities ranging from 65 to 80% of 1 RM at slow controlled speed, whereas CTP trained at intensities ranging from 40 to 60% of 1 RM at maximal intentional speed. Lower body one-repetition maximum (1 RM), isometric rate of force development (RFD), countermovement jump (CMJ) muscle power output, quadriceps femoris muscles thickness (QF MT), and peak oxygen uptake (VO) were assessed before training and after 8 and 16 weeks of CT.

Results: Groups improved similarly in all primary outcomes (P < 0.05), with mean increases ranging: 1 RM (from 39.4 to 75.8%); RFD (from 9.9 to 64.8%); and CMJ muscle power (from 1.8 to 5.2%). Significant increases (P < 0.05) were observed in all secondary outcomes (QF MT, specific tension and VO) with no differences between groups.

Conclusion: CT models were effective for improving maximal and explosive force (1 RM, RFD, and CMJ power), QF MT, and VO. Moreover, despite that using lower loading intensities, PT induced similar adaptations to those of TST.
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http://dx.doi.org/10.1007/s00421-020-04355-zDOI Listing
May 2020

Effect of blood-flow restricted vs heavy-load strength training on muscle strength: Systematic review and meta-analysis.

Scand J Med Sci Sports 2020 May 21;30(5):837-848. Epub 2020 Feb 21.

Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.

Introduction: Heavy-load strength training (HLT) is generally considered the Gold Standard exercise modality for inducing gains in skeletal muscle strength. However, use of heavy external exercise loads may be contraindicative in frail individuals. Low-load resistance exercise combined with partial blood-flow restriction (LL-BFR exercise) may offer an effective alternative for increasing mechanical muscle strength and size. The aim of this study was to compare the effect of LL-BFR training to HLT on maximal muscle strength gains. Prospero registration-id (CRD42014013382).

Materials And Methods: A systematic search in six healthcare science databases and reference lists was conducted. Data selected for primary analysis consisted of post-intervention changes in maximal muscle strength. A random-effects meta-analysis with standardized mean differences (SMD) was used.

Results: Of 1413 papers identified through systematic search routines, sixteen papers fulfilled the inclusion criteria, totalling 153 participants completing HLT and 157 completing LL-BFR training. The magnitude of training-induced gains in maximal muscle strength did not differ between LL-BFR training and HLT (SMD of -0.17 (95% CI: -0.40; 0.05)). Low between-study heterogeneity was noted (I  = 0.0%, Chi P = 9.65).

Conclusion: Low-load blood-flow-restricted training appears equally effective of producing gains in maximal voluntary muscle strength compared to HLT in 20- to 80-year-old healthy and habitually active adults.
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http://dx.doi.org/10.1111/sms.13632DOI Listing
May 2020
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