Publications by authors named "Marko S Laaksonen"

23 Publications

  • Page 1 of 1

Laboratory-Based Factors Predicting Skiing Performance in Female and Male Biathletes.

Front Sports Act Living 2020 5;2:99. Epub 2020 Aug 5.

Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.

Skiing in biathlon is a high-intensity, intermittent endurance discipline. This study aimed to evaluate the relationships between laboratory-derived physiological variables and skiing performance during a field-based biathlon competition (BC) for female and male biathletes. Fourteen female (23 ± 3 year, O 56 ± 4 mL·kg·min) and 14 male (24 ± 4 year, O 66 ± 3 mL·kg·min) biathletes performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing for the assessment of oxygen uptake at a lactate threshold of 4 mmol·L ( O), gross efficiency (GE), aerobic (MR) and anaerobic (MR) metabolic rates, peak oxygen consumption ( O), anaerobic capacity and TT performance. Field-based skiing performance was assessed during a BC. The TT and BC skiing performances were significantly correlated in both sexes ( = 0.68-0.69, < 0.01). O (31/21%), anaerobic capacity (1/0%), and GE (35/32%) explained 67 and 52% of the variance in BC skiing performance for the females ( < 0.01) and males ( = 0.051), respectively. A second model showed that O (30/35%), anaerobic capacity (0/0%) and GE (37/13%) explained 67 and 48% of the variance in BC skiing performance for the females ( < 0.01) and males ( = 0.077), respectively. Results of this study suggest that a high O and GE, but not anaerobic capacity, are important for BC skiing performance, especially for females. In addition, a laboratory-based TT could be useful for regular laboratory testing of biathletes due to its relationship with field-based skiing performance in biathlon.
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http://dx.doi.org/10.3389/fspor.2020.00099DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7739653PMC
August 2020

Aiming strategy affects performance-related factors in biathlon standing shooting.

Scand J Med Sci Sports 2021 Mar 8;31(3):573-585. Epub 2020 Nov 8.

Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.

This study focused on investigating differences in shooting performance and performance-related factors between two different aiming strategies (HOLD, low radial velocity during the approach 0.4-0.2 seconds before triggering, and TIMING, high radial velocity) in biathlon standing shooting. A total of 23 biathletes fired 8 × 5 standing shots at rest (REST) and 2 × 5 shots during a race simulation (RACE). Shooting performance (hit point distance from the center of the target), aiming point trajectory and postural balance were measured from each shot. Shooting performance was similar both at REST (HOLD 33 ± 5 mm vs TIMING 38 ± 8 mm, P = .111) and in RACE (40 ± 11 mm vs 47 ± 12 mm, P = .194). Better shooting performance was related to smaller distance of the aiming point mean location (REST r = 0.93, P < .001, RACE r = 0.72, P = .018) and higher time spent within ⅔ of the distance of the hit area edge from the center 0.6-0.0 seconds before triggering (REST r=-0.88, P = .001, RACE r=-0.73, P = .016) in HOLD, and to lower aiming point total velocity 0.6-0.0 seconds before triggering (REST r = 0.77, P = .009, RACE r = 0.88, P = .001) and less aiming point movement 0.2-0.0 seconds before triggering (REST r = 0.82, P = .003, RACE r = 0.72, P = .012) in TIMING. Postural balance was related to shooting performance at REST in both groups and in RACE in TIMING. Biathletes using the hold strategy should focus on stabilizing the aiming point before triggering and aiming at the center, whereas biathletes using the timing strategy benefit of decreasing the total velocity during the final approach as well as minimizing the aiming point movement right before triggering.
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http://dx.doi.org/10.1111/sms.13864DOI Listing
March 2021

Physiological Responses to Rifle Carriage During Roller-Skiing in Elite Biathletes.

Front Physiol 2019 19;10:1519. Epub 2019 Dec 19.

The Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.

This study aimed to investigate the physiological factors affected by rifle carriage during biathlon skiing performance, as well as the sex differences associated with rifle carriage. Seventeen national- and international-level biathletes (nine females and eight males; age 23.0 ± 3.3 years, O 59.4 ± 7.6 mL.kg.min) performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing (gear 3, skating technique) on two occasions separated by at least 48 h. One condition involved carrying the rifle on the back (WR) and the other condition no rifle (NR) and the tests were randomized. Submaximal O, skiing speed at 4 mmol.L of blood lactate (speed), gross efficiency (GE), aerobic (MR), and anaerobic (MR) metabolic rates, and O were determined. Submaximal O (at all intensities) and GE (16.7 ± 0.9 vs. 16.5 ± 1.1%) were higher for WR compared to NR ( < 0.05), while speed was lower (3.1 ± 0.4 vs. 3.3 ± 0.5 m.s, = 0.040). TT performance was improved (4.6 ± 0.4 vs. 4.3 ± 0.4 m.s, < 0.001) and MR was higher (31.3 ± 8.0 vs. 27.5 ± 6.5 kJ.min, < 0.01) for NR compared to WR, with no difference in O or MR. For skiing WR, TT performance was correlated to speed ( = 0.81, < 0.001), MR ( = 0.65, < 0.01), O ( = 0.51, < 0.05), and relative muscle ( = 0.67, < 0.01) and fat ( = -0.67, < 0.01) masses. Speed together with MR explained more than 80% of the variation in TT performance (WR 84%, NR 81%). Despite a higher relative mass of the rifle in females compared with males (5.6 ± 0.4 vs. 5.0 ± 0.4% of body mass, = 0.012), there were no sex differences associated with rifle carriage measured as absolute or relative differences. Rifle carriage in biathlon skiing led to significantly higher physiological demands during submaximal exercise and reduced performance during maximal treadmill roller-skiing compared to NR for both sexes. The most important variables for performance in biathlon treadmill skiing seem to be speed combined with MR, both of which were lower for WR compared to NR. To improve skiing performance in biathlon, improving speed at 4 mmol.L of blood lactate and anaerobic energy delivery while carrying the rifle are recommended.
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http://dx.doi.org/10.3389/fphys.2019.01519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6951403PMC
December 2019

The influence of physiobiomechanical parameters, technical aspects of shooting, and psychophysiological factors on biathlon performance: A review.

J Sport Health Sci 2018 Oct 8;7(4):394-404. Epub 2018 Sep 8.

Department of Sport Science and Kinesiology, Paris Lodron University of Salzburg, Salzburg 5020, Austria.

The biathlon, an Olympic sporting discipline that combines cross-country skiing with rifle marksmanship, entails considerable physiological demands, as well as fine motor control while shooting after intense exercise and under mental pressure. Although much of our knowledge about cross-country skiing is probably also applicable to the biathlon, carrying the rifle and shooting under stress make this discipline somewhat unique. The present review summarizes and examines the scientific literature related to biathlon performance, with a focus on physiological and biomechanical factors and shooting technique, as well as psychophysiological aspects of shooting performance. We conclude with suggestions for future research designed to extend our knowledge about the biathlon, which is presently quite limited.
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http://dx.doi.org/10.1016/j.jshs.2018.09.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234024PMC
October 2018

Muscle Free Fatty-Acid Uptake Associates to Mechanical Efficiency During Exercise in Humans.

Front Physiol 2018 21;9:1171. Epub 2018 Aug 21.

Turku PET Centre, University of Turku, Turku, Finland.

Intrinsic factors related to muscle metabolism may explain the differences in mechanical efficiency (ME) during exercise. Therefore, this study aimed to investigate the relationship between muscle metabolism and ME. Totally 17 healthy recreationally active male participants were recruited and divided into efficient (EF; = 8) and inefficient (IE; = 9) groups, which were matched for age (mean ± SD 24 ± 2 vs. 23 ± 2 years), BMI (23 ± 1 vs. 23 ± 2 kg m), physical activity levels (3.4 ± 1.0 vs. 4.1 ± 1.0 sessions/week), and Opeak (53 ± 3 vs. 52 ± 3 mL kg min), respectively, but differed for ME at 45% of Opeak intensity during submaximal bicycle ergometer test (EF 20.5 ± 3.5 vs. IE 15.4 ± 0.8%, < 0.001). Using positron emission tomography, muscle blood flow (BF) and uptakes of oxygen (m O), fatty acids (FAU) and glucose (GU) were measured during dynamic submaximal knee-extension exercise. Workload-normalized BF (EF 35 ± 14 vs. IE 34 ± 11 mL 100 g min, = 0.896), m O (EF 4.1 ± 1.2 vs. IE 3.9 ± 1.2 mL 100 g min, = 0.808), and GU (EF 3.1 ± 1.8 vs. IE 2.6 ± 2.3 μmol 100 g min, = 0.641) as well as the delivery of oxygen, glucose, and FAU, as well as respiratory quotient were not different between the groups. However, FAU was significantly higher in EF than IE (3.1 ± 1.7 vs. 1.7 ± 0.6 μmol 100 g min, = 0.047) and it also correlated with ME ( = 0.56, = 0.024) in the entire study group. EF group also demonstrated higher use of plasma FAU than IE, but no differences in use of plasma glucose and intramuscular energy sources were observed between the groups. These findings suggest that the effective use of plasma FAU is an important determinant of ME during exercise.
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http://dx.doi.org/10.3389/fphys.2018.01171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110921PMC
August 2018

The Olympic Biathlon - Recent Advances and Perspectives After Pyeongchang.

Front Physiol 2018 2;9:796. Epub 2018 Jul 2.

Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.

The biathlon, combining cross-country ski skating with rifle marksmanship, has been an Olympic event since the Winter Games in Squaw Valley, United States, in 1960. As a consequence of replacing the classical with the skating technique in the 1980s, as well as considerable improvements in equipment and preparation of ski tracks and more effective training, the average biathlon skiing speed has increased substantially. Moreover, the mass-start, pursuit, and sprint races have been introduced. Indeed, two of the four current individual Olympic biathlon competitions involve mass-starts, where tactics play a major role and the outcome is often decided during the last round of shooting or final sprint. Biathlon is a demanding endurance sport requiring extensive aerobic capacity. The wide range of speeds and slopes involved requires biathletes to alternate continuously between and adapt different skating sub-techniques during races, a technical complexity that places a premium on efficiency. Although the relative amounts of endurance training at different levels of intensity have remained essentially constant during recent decades, today's biathletes perform more specific endurance training on roller skis on terrain similar to that used for competition, with more focus on the upper-body, systematic strength and power training and skiing at higher speeds. Success in the biathlon also requires accurate and rapid shooting while simultaneously recovering from high-intensity skiing. Many different factors, including body sway, triggering behavior, and even psychology, influence the shooting performance. Thus, the complexity of biathlon deserves a greater research focus on areas such as race tactics, skating techniques, or shooting process.
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http://dx.doi.org/10.3389/fphys.2018.00796DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6036135PMC
July 2018

Technical determinants of biathlon standing shooting performance before and after race simulation.

Scand J Med Sci Sports 2018 Jun 9;28(6):1700-1707. Epub 2018 Mar 9.

Faculty of Sport and Health Sciences, Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.

The aim of this study was to identify performance-determining factors in biathlon standing shooting in rest and after intense exercise. Eight Finnish national- and nine junior-team biathletes participated in the study. Participants fired 40 resting shots (REST) and 2 × 5 competition simulation shots (LOAD) after 5 minutes of roller skiing at 95% of peak heart rate. Hit percentage, aiming point trajectory and postural balance were measured from each shot. Cleanness of triggering (ATV, movement of the aiming point 0-0.2 second before the shot) and vertical stability of hold (DevY) were the most important components affecting shooting performance both in REST (DevY, R = -0.61, P < .01; ATV, R = -0.65, P < .01) and in LOAD (DevY, R = -0.50, P < .05; ATV, R = -0.77, P < .001). Postural balance, especially in shooting direction, was related to DevY and ATV. Stability of hold in horizontal (F(1,15) = 7.025, P < .05) and vertical (F(1,15) = 21.285, P < .001) directions, aiming accuracy (F(1,15) = 9.060, P < .01), and cleanness of triggering (F(1,15) = 59.584, P < .001) decreased from REST to LOAD, accompanied by a decrease in postural balance. National- and junior-team biathletes differed only in hit percentage in REST (92 ± 8% vs 81 ± 8%, P < .05) and left leg postural balance in shooting direction in LOAD (0.31 ± 0.18 mm vs 0.52 ± 0.20 mm, P < .05), and the intense exercise affected the shooting technical components similarly in both national and junior groups. Biathletes should focus on cleanness of triggering and vertical stability of hold in order to improve biathlon standing shooting performance. More stable postural balance in shooting direction could help to improve these shooting technical components.
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http://dx.doi.org/10.1111/sms.13072DOI Listing
June 2018

VO(2peak), myocardial hypertrophy, and myocardial blood flow in endurance-trained men.

Med Sci Sports Exerc 2014 Aug;46(8):1498-505

1Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, SWEDEN; 2Turku Positron Emission Tomography Centre, University of Turku and Turku University Hospital, Turku, FINLAND; 3Department of Clinical Physiology and Nuclear Medicine, University of Turku and Turku University Hospital, Turku, FINLAND; and 4Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku and Turku University Hospital, Turku, FINLAND.

Introduction: Endurance training induces cardiovascular and metabolic adaptations, leading to enhanced endurance capacity and exercise performance. Previous human studies have shown contradictory results in functional myocardial vascular adaptations to exercise training, and we hypothesized that this may be related to different degrees of hypertrophy in the trained heart.

Methods: We studied the interrelationships between peak aerobic power (V˙O2peak), myocardial blood flow (MBF) at rest and during adenosine-induced vasodilation, and parameters of myocardial hypertrophy in endurance-trained (ET, n = 31) and untrained (n = 17) subjects. MBF and myocardial hypertrophy were studied using positron emission tomography and echocardiography, respectively.

Results: Both V˙O2peak (P < 0.001) and left ventricular (LV) mass index (P < 0.001) were higher in the ET group. Basal MBF was similar between the groups. MBF during adenosine was significantly lower in the ET group (2.88 ± 1.01 vs 3.64 ± 1.11 mL·g·min, P < 0.05) but not when the difference in LV mass was taken into account. V˙O2peak correlated negatively with adenosine-stimulated MBF, but when LV mass was taken into account as a partial correlate, this correlation disappeared.

Conclusions: The present results show that increased LV mass in ET subjects explains the reduced hyperemic myocardial perfusion in this subject population and suggests that excessive LV hypertrophy has negative effect on cardiac blood flow capacity.
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http://dx.doi.org/10.1249/MSS.0000000000000264DOI Listing
August 2014

Changes in performance and poling kinetics during cross-country sprint skiing competition using the double-poling technique.

Sports Biomech 2013 Nov;12(4):355-64

Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.

In this study, changes in skiing performance and poling kinetics during a simulated cross-country sprint skiing competition were investigated. Twelve elite male cross-country skiers performed simulated sprint competition (4 x 1,150 m heat with 20 min recovery between the heats) using the double-poling technique. Vertical and horizontal pole forces and cycle characteristics were measured using a force plate system (20-m long) during the starting spurt, racing speed, and finishing spurt of each heat. Moreover, heat and 20-m phase velocities were determined. Vertical and horizontal pole impulses as well as mean cycle length were calculated. The velocities of heats decreased by 2.7 +/- 1.7% (p = 0.003) over the simulated competition. The 20-m spurting velocity decreased by 16 +/- 5% (p < 0.002) and poling time increased by 18 +/- 9% (p < 0.003) in spurt phases within heats. Vertical and horizontal poling impulses did not change significantly during the simulation; however, the mean forces decreased (p < 0.039) (vertical by 24 +/- 11% and horizontal by 20 +/- 10%) within heats but not between the heats. Decreased heat velocities over the simulated sprint and spurting velocities within heats indicated fatigue among the skiers. Fatigue was also manifested by decreased pole force production and increased poling time.
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http://dx.doi.org/10.1080/14763141.2013.784798DOI Listing
November 2013

Squeezing the muscle: compression clothing and muscle metabolism during recovery from high intensity exercise.

PLoS One 2013 17;8(4):e60923. Epub 2013 Apr 17.

Department of Sport Science, University of Wuppertal, Wuppertal, Germany.

The purpose of this experiment was to investigate skeletal muscle blood flow and glucose uptake in m. biceps (BF) and m. quadriceps femoris (QF) 1) during recovery from high intensity cycle exercise, and 2) while wearing a compression short applying ~37 mmHg to the thigh muscles. Blood flow and glucose uptake were measured in the compressed and non-compressed leg of 6 healthy men by using positron emission tomography. At baseline blood flow in QF (P = 0.79) and BF (P = 0.90) did not differ between the compressed and the non-compressed leg. During recovery muscle blood flow was higher compared to baseline in both compressed (P<0.01) and non-compressed QF (P<0.001) but not in compressed (P = 0.41) and non-compressed BF (P = 0.05; effect size = 2.74). During recovery blood flow was lower in compressed QF (P<0.01) but not in BF (P = 0.26) compared to the non-compressed muscles. During baseline and recovery no differences in blood flow were detected between the superficial and deep parts of QF in both, compressed (baseline P = 0.79; recovery P = 0.68) and non-compressed leg (baseline P = 0.64; recovery P = 0.06). During recovery glucose uptake was higher in QF compared to BF in both conditions (P<0.01) with no difference between the compressed and non-compressed thigh. Glucose uptake was higher in the deep compared to the superficial parts of QF (compression leg P = 0.02). These results demonstrate that wearing compression shorts with ~37 mmHg of external pressure reduces blood flow both in the deep and superficial regions of muscle tissue during recovery from high intensity exercise but does not affect glucose uptake in BF and QF.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0060923PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3629206PMC
November 2013

Skiing economy and efficiency in recreational and elite cross-country skiers.

J Strength Cond Res 2013 May;27(5):1239-52

Swedish Winter Sports Research Center, Department of Engineering and Sustainable Development, Mid Sweden University, Östersund, Sweden.

The purpose of this study was to investigate and compare skiing economy and gross efficiency in cross-country skiers of different performance levels, ages and genders; male recreational skiers and elite senior and junior cross-country skiers of both genders. The skiers performed tests involving roller skiing on a treadmill using the gear 3 and diagonal stride techniques. The elite cross-country skiers were found to have better skiing economy and higher gross efficiency (5-18%) compared with the recreational skiers (p < 0.05) and the senior elite had better economy and higher efficiency (4-5%) than their junior counterparts (p < 0.05), whereas no differences could be found between the genders. Also, large ranges in economy and gross efficiency were found in all groups. It was concluded that, in addition to V[Combining Dot Above]O2peak, skiing economy and gross efficiency have a great influence on the differences in performance times between recreational and junior and senior elite cross-country skiers, as well as between individual skiers within the different categories. Thus, we recommend cross-country skiers at all performance levels to test not only V[Combining Dot Above]O2peak, but also skiing economy and efficiency.
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http://dx.doi.org/10.1519/JSC.0b013e31824f206cDOI Listing
May 2013

Evidence of improved shooting precision in biathlon after 10 weeks of combined relaxation and specific shooting training.

Cogn Behav Ther 2011 24;40(4):237-50. Epub 2011 Oct 24.

Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University Campus, Östersund, Sweden.

The aim of this study was to test the hypothesis that a combined relaxation (applied tension release, ATR) and specific shooting training regimen may enhance shooting ability of biathlon athletes. Seven biathletes of high national level were randomized into an experimental group (age 20 ± 5 years; Vo2max 60 ± 8 mL kg(-1) min(-1)) and were asked to add this special training intervention to their regular training for 10 weeks, while five other biathletes served as controls (age 19 ± 2 years; Vo2max 57 ± 10 mL kg(-1) min(-1)). The shooting ability of the subjects was assessed before and after the intervention at rest and after roller skiing on a treadmill in a laboratory-based competition simulating assessment. After the intervention period, the experimental group demonstrated a significantly enhanced shooting performance compared to the control group. No changes in Vo2max or in heart rate and Vo2 responses were observed before and after the intervention in either group and there were no differences between the groups in these parameters. Thus, the preliminary conclusion is that a combination of ATR and specific shooting training seems to be instrumental in enhancing the shooting performance in biathlon.
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http://dx.doi.org/10.1080/16506073.2011.616217DOI Listing
March 2012

Enhanced systolic myocardial function in elite endurance athletes during combined arm-and-leg exercise.

Eur J Appl Physiol 2011 Jun 11;111(6):905-13. Epub 2010 Nov 11.

Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, 831 25 Östersund, Sweden.

The aim here was to employ color tissue velocity imaging (TVI), to test the hypothesis that highly trained endurance athletes exhibit enhanced systolic function of the left ventricular (LV) myocardium both at rest and during combined arm-and-leg exercise in comparison with untrained subjects. For each of the ten elite male (EG) and ten matched control participants (CG), LV dimensions and systolic function were assessed at rest using echocardiography. Subsequently, these subjects exercised continuously on a combined arm-and-leg cycle ergometer for 3 min each at 50, 60, 70, 80, 90 and 100% of VO(2max). Oxygen uptake, heart rate, systolic blood pressure (SBP) and peak contraction systolic velocities of the LV myocardium (PSV) were recorded in the end of each level. At rest, the trained and untrained groups differed with respect to LV dimensions, but not systolic function. At 60-100% VO(2max), the EG group demonstrated both higher PSV and SBP. The observation that the EG athletes had higher PSV than CG during exercise at 60-100% VO(2max), but not at rest or at 50% of VO(2max), suggested an enhanced systolic capacity. This improvement is likely to be due to an enhanced inotropic contractility, which only becomes apparent during exercise.
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http://dx.doi.org/10.1007/s00421-010-1712-3DOI Listing
June 2011

Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise.

Clin Physiol Funct Imaging 2010 Jul 11;30(4):241-9. Epub 2010 May 11.

Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Ostersund, Sweden.

The association between muscle oxygen uptake (VO(2)) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one-legged knee-extension exercise at variable intensities using positron emission tomography and a-v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI-1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI-2). Muscle perfusion and O(2) delivery during HI-1 (26 +/- 5 and 5.4 +/- 1.0 ml 100 g(-1) min(-1)) and HI-2 (28 +/- 4 and 5.8 +/- 0.7 ml 100 g(-1) min(-1)) were similar, but both were higher (P<0.01) than during LOW (15 +/- 3 and 3.0 +/- 0.6 ml 100 g(-1) min(-1)). Muscle VO(2) was also higher during both HI workloads (HI-1 3.3 +/- 0.4 and HI-2 4.1 +/- 0.6 ml 100 g(-1) min(-1)) than LOW (1.4 +/- 0.4 ml 100 g(-1) min(-1); P<0.01) and 25% higher during HI-2 than HI-1 (P<0.05). O(2) extraction was higher during HI workloads (HI-1 62 +/- 7 and HI-2 70 +/- 7%) than LOW (45 +/- 8%; P<0.01). O(2) extraction tended to be higher (P = 0.08) during HI-2 when compared to HI-1. Perfusion was less heterogeneous (P<0.05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one-legged knee-extension exercise at variable intensities, skeletal muscle perfusion and O(2) delivery are unchanged between high-intensity workloads, whereas muscle VO(2) is increased during the second high-intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O(2) delivery and uptake. We propose that the excess muscle VO(2) during the second high-intensity workload is derived from working muscle cells.
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http://dx.doi.org/10.1111/j.1475-097X.2010.00934.xDOI Listing
July 2010

Skeletal muscle mitochondrial DNA content and aerobic metabolism in patients with antiretroviral therapy-associated lipoatrophy.

J Antimicrob Chemother 2010 Jul 5;65(7):1497-504. Epub 2010 May 5.

Department of Medicine, Division of Diabetes, Helsinki University Central Hospital, PO Box 348, FIN-00029 HUS, Helsinki, Finland.

Objectives: To assess whether mitochondrial dysfunction in skeletal muscle characterizes antiretroviral therapy (ART)-associated lipoatrophy (LA).

Methods: A cross-sectional study comparing HIV-infected, antiretroviral-treated patients with LA (n = 5; LA+) and without LA (n = 5; non-LA) was conducted. Positron emission tomography was used to measure blood flow, oxygen extraction and oxygen consumption in quadriceps femoris muscle during rest and aerobic exercise. Mitochondrial DNA (mtDNA) was quantified by PCR. Body composition was measured by dual-energy X-ray absorptiometry and magnetic resonance imaging. All data are given as means +/- SEM.

Results: Compared with the non-LA group, the LA+ group had significantly less limb fat and more intra-abdominal fat, but similar leg muscle mass. The LA+ group versus the non-LA group had reduced mtDNA content per nucleus in adipose tissue (173 +/- 38 versus 328 +/- 62; P = 0.067), but not in skeletal muscle (2606 +/- 375 versus 2842 +/- 309; P = 0.64). Perfusion in resting muscle (34 +/- 7 versus 28 +/- 6 mL/kg/min in the LA+ group versus the non-LA group; P = 0.5), and the mean absolute (277 +/- 30 versus 274 +/- 43 mL/kg/min, respectively; P = 0.95) and relative (10.6 +/- 2.5- versus 11.9 +/- 1.5-fold change, respectively; P = 0.67) increases in perfusion during exercise were similar between the groups. Oxygen consumption at rest (2.2 +/- 0.7 versus 2.1 +/- 0.3 mL/kg/min in the LA+ group versus the non-LA group; P = 0.9), and the mean absolute (14.6 +/- 1.7 versus 24.3 +/- 8.8 mL/kg/min, respectively; P = 0.3) and relative (10.3 +/- 2.8- versus 11.7 +/- 2.4-fold change, respectively; P = 0.73) exercise-induced increases in oxygen consumption were similar between the groups. The oxygen extraction fraction was comparable between the groups, both at rest and during exercise. Plasma lactate concentrations remained unchanged in both groups during exercise.

Conclusions: HIV-infected patients with ART-associated LA have similar mtDNA content in skeletal muscle and comparable skeletal muscle aerobic exercise metabolism to antiretroviral-treated non-lipoatrophic patients.
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http://dx.doi.org/10.1093/jac/dkq138DOI Listing
July 2010

Myocardial perfusion during exercise in endurance-trained and untrained humans.

Am J Physiol Regul Integr Comp Physiol 2007 Aug 23;293(2):R837-43. Epub 2007 May 23.

Turku PET Centre, University of Turku, Turku, Finland.

Because of technical challenges very little is known about absolute myocardial perfusion in humans in vivo during physical exercise. In the present study we applied positron emission tomography (PET) in order to 1) investigate the effects of dynamic bicycle exercise on myocardial perfusion and 2) clarify the possible effects of endurance training on myocardial perfusion during exercise. Myocardial perfusion was measured in endurance-trained and healthy untrained subjects at rest and during absolutely the same (150 W) and relatively similar [70% maximal power output (W(max))] bicycle exercise intensities. On average, the absolute myocardial perfusion was 3.4-fold higher during 150 W (P < 0.001) and 4.9-fold higher during 70% W(max) (P < 0.001) than at rest. At 150 W myocardial perfusion was 46% lower in endurance-trained than in untrained subjects (1.67 +/- 0.45 vs. 3.00 +/- 0.75 ml x g(-1) x min(-1); P < 0.05), whereas during 70% W(max) perfusion was not significantly different between groups (P = not significant). When myocardial perfusion was normalized with rate-pressure product, the results were similar. Thus, according to the present results, myocardial perfusion increases in parallel with the increase in working intensity and in myocardial work rate. Endurance training seems to affect myocardial blood flow pattern during submaximal exercise and leads to more efficient myocardial pump function.
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http://dx.doi.org/10.1152/ajpregu.00771.2006DOI Listing
August 2007

Functional evaluation of microvascular free flaps with positron emission tomography.

J Plast Reconstr Aesthet Surg 2006 ;59(2):158-65

Department of Otorhinolaryngology, Head and Neck Surgery, Turku University Central Hospital, FIN-20521 Turku, Finland.

Background: The aim of this study was to assess blood flow (BF) of microvascular free flaps studied with positron emission tomography (PET) in patients with head and neck squamous cell cancer (HNSCC) undergoing major radical surgery 3-4 weeks after high-dose radiotherapy.

Methods: Five patients underwent resection of the HNSCC of the oral cavity followed by microvascular reconstruction with a radial forearm flap. Regional BF in oral and neck tissues was measured with PET using radiolabelled water ([15O]H2O) twice (1-2 and 12-14 days, respectively) following radical surgery.

Results: In the first postoperative PET study, the median BF in the cutaneous flap area was 5.1 mL/100 g/min, and in the muscle contra-lateral to the recipient site 19.9 mL/100 g/min. A low flap-to-muscle BF ratio appeared to correlate with circulatory incongruity, and thus with poorer flap success. The follow-up study on the second postoperative week supported the results of the primary PET scan.

Conclusions: This pilot study suggests that PET using [15O]H2O is a feasible method to quantitatively evaluate BF of the whole free flap in patients operated on for oral
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http://dx.doi.org/10.1016/j.bjps.2005.04.016DOI Listing
June 2006

The association between muscle EMG and perfusion in knee extensor muscles.

Clin Physiol Funct Imaging 2006 Mar;26(2):99-105

Turku PET Centre, University of Turku, Finland.

The relationships between electromyographic (EMG) activity and force as well as muscle blood flow and work have been well established. However, the association between muscle blood flow and EMG activity remains unsolved. Thus, to test the hypothesis that muscle EMG activity relates to muscle perfusion in different compartments of the quadriceps femoris (QF) muscle, 12 healthy male subjects were studied. During two very submaximal exercise bouts, at different exercise intensities, oxygen labelled radiowater and positron emission tomography were used to measure muscle perfusion. In addition, produced force of knee extensors and muscle EMG activity in the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were recorded during both exercise bouts. Although the exercise intensity and average force production was higher during the second exercise bout (38 +/- 15 versus 51 +/- 17 N; P = 0.007), the mean EMG activity was lower (RF; P<0.001) or unchanged (VL; P = 0.722 and VM; P = 0.640). During the second exercise period, perfusion also remained unchanged in the entire QF muscle (P = 0.223) and in its separate muscles (VL, P = 0.703; VM, P = 0.141; RF, P = 0.113) in a group level. However, the individual changes in muscle perfusion were tightly related to changes in muscle EMG activity in VL (r = 0.84; P = 0.002) and VM (r = 0.68; P = 0.015) but poorly in the RF muscle (r = 0.40; P = 0.257). In conclusion, the different associations between muscle perfusion and EMG activity in different QF muscles suggests specific functional role of the vasti muscles and the RF muscle.
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http://dx.doi.org/10.1111/j.1475-097X.2006.00656.xDOI Listing
March 2006

Motion detection and correction for dynamic ( 15)O-water myocardial perfusion PET studies.

Eur J Nucl Med Mol Imaging 2005 Dec 3;32(12):1378-83. Epub 2005 Sep 3.

Turku PET Centre, University of Turku, P.O. Box 52, 20521 Turku, Finland.

Purpose: Patient motion during dynamic PET studies is a well-documented source of errors. The purpose of this study was to investigate the incidence of frame-to-frame motion in dynamic ( 15)O-water myocardial perfusion PET studies, to test the efficacy of motion correction methods and to study whether implementation of motion correction would have an impact on the perfusion results.

Methods: We developed a motion detection procedure using external radioactive skin markers and frame-to-frame alignment. To evaluate motion, marker coordinates inside the field of view were determined in each frame for each study. The highest number of frames with identical spatial coordinates during the study were defined as "non-moved". Movement was considered present if even one marker changed position, by one pixel/frame compared with reference, in one axis, and such frames were defined as "moved". We tested manual, in-house-developed motion correction software and an automatic motion correction using a rigid body point model implemented in MIPAV (Medical Image Processing, Analysis and Visualisation) software. After motion correction, remaining motion was re-analysed. Myocardial blood flow (MBF) values were calculated for both non-corrected and motion-corrected datasets.

Results: At rest, patient motion was found in 18% of the frames, but during pharmacological stress the fraction increased to 45% and during physical exercise it rose to 80%. Both motion correction algorithms significantly decreased (p<0.006) the number of moved frames and the amplitude of motion (p<0.04). Motion correction significantly increased MBF results during bicycle exercise (p<0.02). At rest or during adenosine infusion, the motion correction had no significant effects on MBF values.

Conclusion: Significant motion is a common phenomenon in dynamic cardiac studies during adenosine infusion but especially during exercise. Applying motion correction for the data acquired during exercise clearly changed the MBF results, indicating that motion correction is required for these studies.
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http://dx.doi.org/10.1007/s00259-005-1846-4DOI Listing
December 2005

Myocardial perfusion after marathon running.

Scand J Med Sci Sports 2004 Aug;14(4):208-14

Turku PET Centre, University of Turku, Turku, Finland.

We investigated the effects of acute prolonged exercise (marathon running) on cardiac function and myocardial perfusion. Cardiac dimensions and function were measured in seven endurance-trained men using echocardiography before and repeatedly after marathon (42.2 km) running (at 10 min, 150 min, and 20 h). Myocardial perfusion and perfusion resistance were measured using positron emission tomography and 15O-H2O before and 85-115 min after running. Echocardiographic indices showed only mild and clinically non-significant changes in cardiac function after running. Rate-pressure-corrected basal myocardial perfusion (0.89+/-0.13 vs. 1.20+/-0.32 mL min(-1) g(-1), P=0.04) was increased after running. Also, adenosine-stimulated perfusion tended to be higher (3.67+/-0.81 vs. 4.47+/-0.52 mL min(-1) g(-1), P=0.12) and perfusion resistance during adenosine stimulation was significantly lower after running (26+/-6 vs. 18+/-3 mmHg min g mL(-1), P=0.03). Plasma free fatty acid (FFA) concentration was significantly increased after running. These results show that marathon running does not cause marked changes in cardiac function in healthy men. Basal perfusion was increased after exercise, probably reflecting changes in fuel preferences to increased use of FFAs. Strenuous exercise also seems to enhance coronary reactivity, which could thereby serve as a protective mechanism to vascular events after exercise.
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http://dx.doi.org/10.1111/j.1600-0838.2004.00357.xDOI Listing
August 2004

Muscle fractal vascular branching pattern and microvascular perfusion heterogeneity in endurance-trained and untrained men.

J Physiol 2003 Jan;546(Pt 2):529-35

Turku PET Centre, University of Turku, FIN-20521 Turku, Finland.

Less heterogeneous skeletal muscle perfusion has recently been reported in endurance-trained compared to untrained men at macrovascular level. The causes of this difference in perfusion heterogeneity are unknown as is whether the same difference is observed in microvasculature. We hypothesised that the difference could be caused by changes in muscle vascular branching pattern. Perfusion was measured in resting and exercising muscle in 14 endurance-trained and seven untrained men using [(15)O]water and positron emission tomography. Fractal dimension (D) of perfusion distribution was calculated as a measure of fractal characteristics of muscle vascular branching pattern. Perfusion heterogeneity in microvascular units (1 mm(3) samples) was estimated using the measured heterogeneity in voxels of positron emission tomography (PET) images (relative dispersion, RD = S.D./mean) and corresponding D values. D was similar between the groups (exercising muscle 1.11 +/- 0.07 and 1.14 +/- 0.06, resting muscle 1.12 +/- 0.06 and 1.14 +/- 0.03, trained and untrained, respectively). Trained men had lower perfusion (151 +/- 44 vs. 218 +/- 87 ml min(-1) kg(-1), P < 0.05) and macrovascular perfusion heterogeneity (relative dispersion 21 +/- 5 vs. 25 +/- 5 %, P < 0.05) in exercising muscle than untrained men. Furthermore, estimated perfusion heterogeneity in microvascular units in exercising muscle was also lower in trained men (33 +/- 7 vs.48 +/- 19 %, P < 0.05). These results show that fractal vascular branching pattern is similar in endurance-trained and untrained men but perfusion is less heterogeneous at both the macro- and the microvascular level in endurance-trained men. Thus, changes in fractal branching pattern do not explain the differences in perfusion heterogeneity between endurance-trained and untrained men.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2342530PMC
http://dx.doi.org/10.1113/jphysiol.2002.030882DOI Listing
January 2003

Skeletal muscle blood flow and flow heterogeneity during dynamic and isometric exercise in humans.

Am J Physiol Heart Circ Physiol 2003 Mar 21;284(3):H979-86. Epub 2002 Nov 21.

Turku Positron Emission Tomography Centre, University of Turku, FIN-20521 Turku, Finland.

The effects of dynamic and intermittent isometric knee extension exercises on skeletal muscle blood flow and flow heterogeneity were studied in seven healthy endurance-trained men. Regional muscle blood flow was measured using positron emission tomography (PET) and an [(15)O]H(2)O tracer, and electromyographic (EMG) activity was recorded in the quadriceps femoris (QF) muscle during submaximal intermittent isometric and dynamic exercises. QF blood flow was 61% (P = 0.002) higher during dynamic exercise. Interestingly, flow heterogeneity was 13% (P = 0.024) lower during dynamic compared with intermittent isometric exercise. EMG activity was significantly higher (P < 0.001) during dynamic exercise, and the change in EMG activity from isometric to dynamic exercise was tightly related to the change in blood flow in the vastus lateralis muscle (r = 0.98, P < 0.001) but not in the rectus femoris muscle (r = -0.09, P = 0.942). In conclusion, dynamic exercise causes higher and less heterogeneous blood flow than intermittent isometric exercise at the same exercise intensity. These responses are, at least partly, related to the increased EMG activity.
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http://dx.doi.org/10.1152/ajpheart.00714.2002DOI Listing
March 2003

Muscle oxygen extraction and perfusion heterogeneity during continuous and intermittent static exercise.

J Appl Physiol (1985) 2003 Mar 25;94(3):953-8. Epub 2002 Oct 25.

Turku Positron Emission Tomography Centre, and Department of Medicine, University of Turku, FIN-20521 Turku, Finland.

The purpose of this study was to compare the effects of intermittent and continuous static exercise on muscle perfusion, perfusion heterogeneity, and oxygen extraction. Perfusion and oxygen uptake of quadriceps femoris muscle were measured in 10 healthy men by using positron emission tomography and [(15)O]H(2)O and [(15)O]O(2) first during intermittent static exercise [10% of maximal static force (MSF)] and thereafter during continuous static exercise at the same tension-time level (5% static; 5% of MSF). In 4 of these subjects, perfusion was measured during continuous static exercise with 10% of MSF (10% continuous) instead of the second [(15)O]O(2) measurement. Muscle oxygen consumption was similar during intermittent and 5% continuous, but muscle perfusion was significantly higher during 5% continuous. Consequently, muscle oxygen extraction fraction was lower during 5% continuous. Perfusion was also more heterogeneous during 5% continuous. When exercise intensity was doubled during continuous static exercise (from 5% continuous to 10% continuous), muscle perfusion increased markedly. These results suggest that continuous, low-intensity static exercise decreases muscle oxygen extraction and increases muscle perfusion and its heterogeneity compared with intermittent static exercise at the same relative exercise intensity.
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http://dx.doi.org/10.1152/japplphysiol.00731.2002DOI Listing
March 2003