Publications by authors named "Floor Groot"

7 Publications

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The relationship between relative aerobic load, energy cost, and speed of walking in individuals post-stroke.

Gait Posture 2021 Sep 21;89:193-199. Epub 2021 Jul 21.

Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, the Netherlands; Heliomare Research and Development, Wijk aan Zee, the Netherlands; University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, the Netherlands.

Background: Individuals post-stroke walk slower than their able-bodied peers, which limits participation. This might be attributed to neurological impairments, but could also be caused by a mismatch between aerobic capacity and aerobic load of walking leading to an unsustainable relative aerobic load at most economic speed and preference for a lower walking speed.

Research Question: What is the impact of aerobic capacity and aerobic load of walking on walking ability post-stroke?

Methods: Forty individuals post-stroke (more impaired N = 21; preferred walking speed (PWS)<0.8 m/s, less impaired N = 19), and 15 able-bodied individuals performed five, 5-minute treadmill walking trials at 70 %, 85 %, 100 %, 115 % and 130 % PWS. Energy expenditure (mlO/kg/min) and energy cost (mlO/kg/m) were derived from oxygen uptake (V˙O). Relative load was defined as energy expenditure divided by peak aerobic capacity (%V˙Opeak) and by V˙O at ventilatory threshold (%V˙O-VT). Relative load and energy cost at PWS were compared with one-way ANOVA's. The effect of speed on these parameters was modeled with Generalized Estimating Equations.

Results: Both more and less impaired individuals post-stroke showed lower PWS than able-bodied controls (0.44 [0.19-0.76] and 1.04 [0.81-1.43] vs 1.36 [0.89-1.53] m/s) and higher relative load at PWS (50.2 ± 14.4 and 51.7 ± 16.8 vs 36.2 ± 7.6 %V˙Opeak and 101.9 ± 20.5 and 97.0 ± 27.3 vs 64.9 ± 13.8 %V˙O-VT). Energy cost at PWS of more impaired (0.30 [.19-1.03] mlO/kg/m) was higher than less-impaired (0.19[0.10-0.24] mlO/kg/m) and able-bodied (0.15 [0.13-0.18] mlO/kg/m). For post-stroke individuals, increasing walking speed above PWS decreased energy cost, but resulted in a relative load above endurance threshold.

Significance: Individuals post-stroke seem to reduce walking speed to prevent unsustainably high relative aerobic loads at the expense of reduced economy. When aiming to improve walking ability post-stroke, it is important to consider training aerobic capacity.
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September 2021

Effects of eccentric exercises on improving ankle dorsiflexion in soccer players.

BMC Musculoskelet Disord 2021 May 26;22(1):485. Epub 2021 May 26.

Department of Orthopaedic Surgery and Sports Medicine, Erasmus MC, University Medical Centre Rotterdam, Doctor Molewaterplein 40, 3015 GD, Rotterdam, The Netherlands.

Purpose: The purpose of this study was to determine the effect of targeted eccentric calf muscle exercises compared to regular training on ankle dorsiflexion in healthy adolescent soccer players with a decreased ankle dorsiflexion.

Methods: Male adolescent players (aged 14-21 years) from two professional soccer clubs were evaluated with the Weight Bearing Dorsiflexion Lunge Test (WBDLT) at baseline and after 12 weeks of this prospective controlled study. One club served as the control group and the other as the intervention group. Players with decreased ankle dorsiflexion (WBDLT) ≤ 10 cm) performed stretching and eccentric calf muscle exercises three times per week next to regular training in the intervention group, and performed only regular training in the control group. Primary outcome was the between-group difference in change in WBDLT between baseline and 12 weeks.

Results: Of 107 eligible players, 47(44 %) had a decreased ankle dorsiflexion. The WBDLT (± standard deviation) increased in the intervention group from 7.1 (± 1.8) to 7.4 (± 2.4) cm (95 % Confidence Interval (CI)[-0.493 to 1.108], p = 0.381) and in the control group from 6.1 (± 2.4) to 8.2 (± 2.9) cm (95 % CI [1.313 to 2.659], p < 0.001). The difference in change of WBDLT between both groups was statistically significant (95 % CI [-2.742 to -0.510], p = 0.005).

Conclusions: Targeted eccentric calf muscle exercises do not increase ankle dorsiflexion in healthy adolescent soccer players. Compared to regular training, eccentric exercises even resulted in a decreased calf muscle flexibility.

Trial Registration: This trial was registered retrospectively on the 7th of September 2016 in The Netherlands Trial Register (ID number: 6044).
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May 2021

[Exercise capacity after mechanical ventilation because of COVID-19: Cardiopulmonary exercise tests in clinical rehabilitation].

Ned Tijdschr Geneeskd 2020 10 29;164. Epub 2020 Oct 29.

Sport- en Beweegkliniek, Haarlem.

Objective: To safely and effectively train the exercise capacity of post-COVID-19 patients it is important to test for cardiopulmonary risk factors and to assess exercise limitations. The goal of this study was to describe the exercise capacity and underlying exercise limitations of mechanically ventilated post-COVID-19 patients in clinical rehabilitation.

Design: A retrospective cohort study.

Method: Twenty-four post-COVID-19patients that were mechanically ventilated at ICU and thereafter admitted for clinical rehabilitation performed a symptom-limited cardiopulmonary exercise test (CPET) with breath-by-breath gas-exchange monitoring, ECG-registration, blood pressure- and saturation monitoring. In absence of a primary cardiac or ventilatory exercise limitation patients were considered to be limited primarily by decreased peripheral muscle mass.

Results: Twenty-three patients could perform a maximal exercise test and no adverse events occurred. Cardiorespiratory fitness was very poor with a median peak oxygen uptake of 15.0 [10.1-21.4] mlO2/kg/min (57% of predicted values). However, we observed large differences within the group in both exercise capacity and exercise limitations. While 7/23 patients were primarily limited by ventilatory function, the majority (70%) was limited primarily by the decreased peripheral muscle mass.

Conclusion: Cardiorespiratory fitness of post-COVID-19 patients in clinical rehabilitation is strongly deteriorated. The majority of patients seemed primarily limited for exercise by the decreased peripheral muscle mass.
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October 2020

Extrafoveal attentional capture by object semantics.

PLoS One 2019 23;14(5):e0217051. Epub 2019 May 23.

Department of Experimental and Applied Psychology & Institute for Brain and Behaviour, Vrije Universiteit, Amsterdam, The Netherlands.

There is ongoing debate on whether object meaning can be processed outside foveal vision, making semantics available for attentional guidance. Much of the debate has centred on whether objects that do not fit within an overall scene draw attention, in complex displays that are often difficult to control. Here, we revisited the question by reanalysing data from three experiments that used displays consisting of standalone objects from a carefully controlled stimulus set. Observers searched for a target object, as per auditory instruction. On the critical trials, the displays contained no target but objects that were semantically related to the target, visually related, or unrelated. Analyses using (generalized) linear mixed-effects models showed that, although visually related objects attracted most attention, semantically related objects were also fixated earlier in time than unrelated objects. Moreover, semantic matches affected the very first saccade in the display. The amplitudes of saccades that first entered semantically related objects were larger than 5° on average, confirming that object semantics is available outside foveal vision. Finally, there was no semantic capture of attention for the same objects when observers did not actively look for the target, confirming that it was not stimulus-driven. We discuss the implications for existing models of visual cognition.
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February 2020

Interrater and intrarater reliability of ventilatory thresholds determined in individuals with spinal cord injury.

Spinal Cord 2019 Aug 28;57(8):669-678. Epub 2019 Feb 28.

University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, the Netherlands.

Study Design: Cross-sectional.

Objectives: Individualized training regimes are often based on ventilatory thresholds (VTs). The objectives were to study: (1) whether VTs during arm ergometry could be determined in individuals with spinal cord injury (SCI), (2) the intrarater and interrater reliability of VT determination.

Setting: University research laboratory.

Methods: Thirty graded arm crank ergometry exercise tests with 1-min increments of recreationally active individuals (tetraplegia (N = 11), paraplegia (N = 19)) were assessed. Two sports physicians assessed all tests blinded, randomly, in two sessions, for VT1 and VT2, resulting in 240 possible VTs. Power output (PO), heart rate (HR), and oxygen uptake (VO) at each VT were compared between sessions or raters using paired samples t-tests, Wilcoxon signed-rank tests, intraclass correlation coefficients (ICC, relative agreement), and Bland-Altman plots (random error, absolute agreement).

Results: Of the 240 VTs, 217 (90%) could be determined. Of the 23 undetermined VTs, 2 (9%) were VT1 and 21 (91%) were VT2; 7 (30%) among individuals with paraplegia, and 16 (70%) among individuals with tetraplegia. For the successfully determined VTs, there were no systematic differences between sessions or raters. Intrarater and interrater ICCs for PO, HR, and VO at each VT were high to very high (0.82-1.00). Random error was small to large within raters, and large between raters.

Conclusions: For VTs that could be determined, relative agreement was high to very high, absolute agreement varied. For some individuals, often with tetraplegia, VT determination was not possible, thus other methods should be considered to prescribe exercise intensity.
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August 2019

High knee loading in male adolescent pre-professional football players: Effects of a targeted training programme.

J Sci Med Sport 2019 Feb 5;22(2):164-168. Epub 2018 Jul 5.

Department of Orthopaedic Surgery, Erasmus University Medical Center Rotterdam, The Netherlands.

Objective: To assess whether targeted neuromuscular exercises can decrease knee loading of adolescent pre-professional footballers with high knee loading as identified with the field-based Drop Vertical Jump Test (DVJT).

Design: Prospective controlled trial, conducted between August and November 2016 at Erasmus Medical Centre, The Netherlands.

Methods: Pre-professional football players (aged 14-21years) were evaluated at baseline and after 12weeks follow-up with the field-based DVJT. The field-based DVJT is a standardised test in which a player drops from a box and jumps up immediately after landing; knee load is calculated based on five parameters. Players with high knee load (probability≥0.75) from one club performed regular training(control group), and players with high knee load from another other club performed targeted neuromuscular exercises for 12weeks (intervention group). The difference of change in knee load between both groups after 12weeks was the primary outcome measure.

Results: Of 107 eligible players, 75 had a high knee loading. Knee loading decreased in both groups after 12weeks of training, but change in probability of high knee load was not significantly different between both groups (95% Confidence Interval [-0.012-0.082], p=0.139).

Conclusion: Targeted neuromuscular exercises had no additional effect in decreasing knee loading of adolescent male pre-professional football players compared to regular training.

Trial Registration Number: The Netherlands Trial Register (ID number: 6044).
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February 2019

When meaning matters: The temporal dynamics of semantic influences on visual attention.

J Exp Psychol Hum Percept Perform 2016 Feb 31;42(2):180-96. Epub 2015 Aug 31.

Department of Cognitive Psychology, VU University.

An important question is, to what extent is visual attention driven by the semantics of individual objects, rather than by their visual appearance? This study investigates the hypothesis that timing is a crucial factor in the occurrence and strength of semantic influences on visual orienting. To assess the dynamics of such influences, the authors presented the target instruction either before or after visual stimulus onset, while eye movements were continuously recorded throughout the search. The results show a substantial but delayed bias in orienting toward semantically related objects compared with visually related objects when target instruction is presented before visual stimulus onset. However, this delay can be completely undone by presenting the visual information before the target instruction (Experiment 1). Moreover, the absence or presence of visual competition does not change the temporal dynamics of the semantic bias (Experiment 2). Visual orienting is thus driven by priority settings that dynamically shift between visual and semantic representations, with each of these types of bias operating largely independently. The findings bridge the divide between the visual attention and the psycholinguistic literature. (PsycINFO Database Record
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February 2016