Sam gained a First Class B. Sc. (Honours) in Sport and Exercise Sciences from The University of Birmingham in 1996. She then worked in the film and television and the finance industries for several years. Along the way Sam gained a Post-graduate certificate in TV and documentary production from the University of Salford and qualified as a Taxation Technician while working for PricewaterhouseCoopers LLP. In 2003 she went to the United States to pursue further study in biomechanics and worked as a Graduate Teaching Assistant while gaining a Master of Science in Kinesiology in 2004, and a Masters in Applied Statistics and a Ph.D. in Kinesiology in 2007. Sam then gained her Post-graduate Certificate in Teaching in Higher Education in 2010 from Aberystwyth University while working there as Lecturer in Biomechanics.
Sam joined the University of Kent in 2012 as a Lecturer teaching biomechanics and statistics and is a member of the International Society of Biomechanics and the American Society of Biomechanics. Her research interests are the mechanical modelling of muscle and tendon in order to understand principles of movement, and the application of biomechanical principles to reduce the harm from falls in older adults. back to top
Pethick, J., Winter, S. and Burnley, M. (2019). Fatigue reduces the complexity of knee extensor torque during fatiguing sustained isometric contractions. European Journal of Sport Science [Online]. Available at: https://doi.org/10.1080/17461391.2019.1599450.
Abstract | View in KAR
The temporal structure, or complexity, of muscle torque output reflects the adaptability of motor control to changes in task demands. This complexity is reduced by neuromuscular fatigue during intermittent isometric contractions. We tested the hypothesis that sustained fatiguing isometric contractions would result in a similar loss of complexity. To that end, nine healthy participants performed, on separate days, sustained isometric contractions of the knee extensors at 20% MVC to task failure and at 100% MVC for 60 s. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling were quantified by calculating approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Global, central and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. Fatigue reduced the complexity of both submaximal (ApEn from 1.02 ± 0.06 to 0.41 ± 0.04, P < 0.05) and maximal contractions (ApEn from 0.34 ± 0.05 to 0.26 ± 0.04, P < 0.05; DFA α from 1.41 ± 0.04 to 1.52 ± 0.03, P < 0.05). The losses of complexity were accompanied by significant global, central and peripheral fatigue (all P < 0.05). These results demonstrate that a fatigue-induced loss of torque complexity is evident not only during fatiguing intermittent isometric contractions, but also during sustained fatiguing contractions.
Pethick, J. et al. (2019). Prolonged depression of knee extensor torque complexity following eccentric exercise. Experimental Physiology [Online] 104:100-111. Available at: https://doi.org/10.1113/EP087295.
Abstract | View in KAR
Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output.
Exercise-induced muscle damage reduces muscle torque output for considerably longer than
high-intensity fatiguing contractions. We hypothesised that muscle damaging eccentric
exercise would lead to a persistent decrease in torque complexity, whereas fatiguing exercise
would not. Ten healthy participants performed five isometric contractions (6 s contraction, 4 s
rest) at 50% maximal voluntary contraction (MVC) before, immediately after, 10, 30 and 60
minutes, and 24 hours after eccentric (muscle damaging) and isometric (fatiguing) exercise.
These contractions were also repeated 48 hours and one week after eccentric exercise. Torque
and surface EMG signals were sampled throughout each test. Complexity and fractal scaling
were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis ?
exponent (DFA ?). Global, central and peripheral perturbations were quantified using MVCs
with femoral nerve stimulation. Complexity decreased following both eccentric (ApEn, mean
(SD), from 0.39 (0.10) to 0.20 (0.12), P < 0.001) and isometric exercise (from 0.41 (0.13) to
0.09 (0.04); P < 0.001). After eccentric exercise ApEn and DFA ? required 24 hours to recover
to baseline levels, but only 10 minutes following isometric exercise. MVC torque remained
reduced (from 233.6 (74.2) to 187.5 (64.7) N.m) 48 hours after eccentric exercise, with such
changes only evident up to 60 minutes following isometric exercise (MVC torque, from 246.1
(77.2) to 217.9 (71.8) N.m). The prolonged depression in maximal muscle torque output is
therefore accompanied by a prolonged reduction in torque complexity.
Winter, S. et al. (2018). A Dual X-Ray Absorptiometry Validated Geometric Model for the Calculation of Body Segment Inertial Parameters of Young Females. Journal of Applied Biomechanics [Online] 34:89-95. Available at: http://dx.doi.org/10.1123/jab.2016-0307.
Abstract | View in KAR | View Full Text
The purpose of this study was to validate a new geometric solids model, developed to address the lack of female specific models for body segment inertial parameter estimation. A second aim was to determine the effect of reducing the number of geometric solids used to model the limb segments on model accuracy. The 'full' model comprised 56 geometric solids, the 'reduced' 31, and the 'basic' 16. Predicted whole-body inertial parameters were compared with direct measurements (reaction board, scales), and predicted segmental parameters with those estimated from whole-body DXA scans for 28 females. The percentage root mean square error (%RMSE) for whole-body volume was <2.5% for all models, and 1.9% for the full model. The %RMSE for whole-body center of mass location was <3.2% for all models. The %RMSE whole-body mass was <3.3% for the full model. The RMSE for segment masses was <0.5 kg (<0.5%) for all segments; Bland-Altman analysis showed the full and reduced models could adequately model thigh, forearm, foot and hand segments, but the full model was required for the trunk segment. The proposed model was able to accurately predict body segment inertial parameters for females, more geometric solids are required to more accurately model the trunk.
For more information about my publications, please visit my Google Scholar and Research Gate profiles. back to top
Sam's previous publications have looked at variability in the in vivo expression of the force-length curves for different muscles. This work involved initially validating a method for determining the limb of the parabolic force-length relationships that a muscle operated over. She then used a modelling approach to determine general principles for identifying the expected variability in this mechanical parameter for different muscles given a knowledge of relative muscle fibre, moment arm and tendon lengths. In order to better model and understand movement Samantha has since undertaken some work to measure and predict body segment inertial parameters in different populations.
Furthermore, Sam is also interested in the application of algorithms from the fields of statistical physics and non-linear dynamics to biomechanics in order to determine principles of movement and adaptation. Some recent work has quantified changes in biomechanical gait and balance characteristics in older adults following postural stability instruction. The focus of the latter work is to identify how strength and balance training should be deployed in community and health care settings to derive the maximum benefits in terms of reducing the harm from falls in older adults. back to top