Reviewing the Variability-Overuse Injury Hypothesis: Does Movement Variability Relate to Landing Injuries?

Purpose: Overuse injuries are common in sport, but complete understanding of injury risk factors remains incomplete. Although biomechanical studies frequently examine musculoskeletal injury mechanisms, human movement variability studies aim to better understand neuromotor functioning, with proposed connections between overuse injury mechanisms and changes in motor variability. Method: In a narrative review, we discuss the variability-overuse injury hypothesis, which suggests repeated load application leads to mechanical tissue breakdown and subsequent injury when exceeding the rate of physiological adaptation. Due to the multidisciplinary nature of this hypothesis, we incorporate concepts from motor control, neurophysiology, biomechanics, as well as research design and data analysis. We therefore summarize multiple perspectives while proposing theoretical relationships between movement variability and lower extremity overuse injuries. Results: Experimental data are presented and summarized from published experiments examining interactions between experimental task demands and movement variability in the context of drop landing movements, along with comparisons to previous movement variability studies. Conclusion: We provide a conceptual framework for sports medicine researchers interested in predicting and preventing sports injuries. Under performance conditions with greater task demands, we predict reduced trial-to-trial movement variability that could increase the likelihood of overuse injuries.     

Transforming in the visiting assistant professor role: collaborative self-study research in physical education teacher education

Transitioning into faculty roles can be a challenging experience. Responsibilities related to teaching, research, and service can be difficult to balance, and mismatch between personal preferences for work focus and instructional expectations can be problematic. This is particularly true of visiting assistant professors who want to work toward tenure-track positions, but whose current job focus is on teaching. Through transformative learning theory and employing the methodologies of self-study, we sought to understand the experiences of Kevin, the second author and a first-year visiting assistant professor. We draw data from Kevin's reflective journal and discussions between Kevin and his critical friend, Jim. Themes included (a) becoming an academic, (b) a hard-wired disposition toward work, and (c) influence of the VAP on emotional and personal health. Results are discussed through the lens of transformative learning theory and focus on Kevin's growth during his year as a visiting assistant professor.     

Considerations for the use of functional principal components analysis in sports biomechanics: examples from on-water rowing

The proliferation of new biomechanical technology in laboratory and field settings facilitates the capture of data-sets consisting of complex time-series. An understanding of the appropriate statistical approaches for analysing and interpreting these data-sets is required and the functional data analysis (FDA) family of statistical techniques has emerged in the biomechanical literature. Given the use of FDA is currently in its infancy with biomechanical data, this paper will form the first of a two part series aiming to address practical issues surrounding the application of FDA techniques in biomechanics. This work focuses on functional principal components analysis (fPCA), which is explored using existing literature and sample data from an on-water rowing database. In particular methodological considerations for the implementation of fPCA such as temporal normalisation of data, removal of unwanted forms of variation in a data-set and documented methods for preserving the original temporal properties within a set of curves are explored in detail as a part of this review. Limitations and strengths of the technique are outlined and recommendations are provided to encourage the appropriate use of fPCA within the field of applied sports biomechanics.     

Numerical modelling of rowing blade hydrodynamics

The highly unsteady flow around a rowing blade in motion is examined using a three-dimensional computational fluid dynamics (CFD) model which accounts for the interaction of the blade with the free surface of the water. The model is validated using previous experimental results for quarter-scale blades held stationary near the surface in a water flume. Steady-state drag and lift coefficients from the quarter-scale blade flume simulation are compared to those from a simulation of the more realistic case of a full-scale blade in open water. The model is then modified to accommodate blade motion by simulating the unsteady motion of the rowing shell moving through the water, and the sweep of the oar blade with respect to the shell. Qualitatively, the motion of the free surface around the blade during a stroke shows a realistic agreement with the actual deformation encountered during rowing. Drag and lift coefficients calculated for the blade during a stroke show that the transient hydrodynamic behaviour of the blade in motion differs substantially from the stationary case.     

Optimized versus corrected peak power during friction-braked cycle ergometry in males and females

The aim of this study was to compare optimization and correction procedures for the determination of peak power output during friction-loaded cycle ergometry. Ten male and 10 female sports students each performed five 10-s sprints from a stationary start on a Monark 864 basket-loaded ergometer. Resistive loads of 5.0, 6.5, 8.0, 9.5, and 11.0% body weight were administered in a counterbalanced order, with a recovery period of 10 min between sprints. Peak power was greater and occurred earlier, with less work having been done before the attainment of peak power, when the data were corrected to account for the inertial and frictional characteristics of the ergometer. Corrected peak power was independent of resistive load (P > 0.05), whereas uncorrected peak power varied as a quadratic function of load (P < 0.001). For males and females, optimized peak power (971 +/- 122 and 668 +/- 37 W) was lower (P < 0.01) than either the highest (1074 +/- 111 and 754 +/- 56 W respectively) or the mean (1007 +/- 125 and 701 +/- 45 W respectively) of the five values for corrected peak power. Optimized and mean corrected peak power were highly correlated both in males (r = 0.97, P < 0.001) and females (r = 0.96, P < 0.001). The difference between optimized and mean corrected peak power was 37 +/- 30 W in males and 33 +/- 14 W in females, of which approximately 15 W was due to the correction for frictional losses. We conclude that corrected peak power is independent of resistive load in males and females.     

Relationship between maximal oxygen uptake and oxygen uptake attained during treadmill middle-distance running

Traditionally, it has been assumed that during middle-distance running oxygen uptake (VO2) reaches its maximal value (VO2max) providing the event is of a sufficient duration; however, this assumption is largely based on observations in individuals with a relatively low VO2max. The aim of this study was to determine whether VO2max is related to the VO2 attained (i.e. VO2peak) during middle-distance running on a treadmill. Fifteen well-trained male runners (age 23.3 +/- 3.8 years, height 1.80 +/- 0.10 m, body mass 76.9 +/- 10.6 kg) volunteered to participate in the study. The participants undertook two 800-m trials to examine the reproducibility of the VO2 response. These two trials, together with a progressive test to determine VO2max, were completed in a randomized order. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest VO2 during the progressive test (i.e. VO2max) was compared with the highest VO2 during the 800-m trials (i.e. VO2peak) to examine the relationship between VO2max and the VO2 attained in the 800-m trials. For the 15 runners, VO2max was 58.9 +/- 7.1 ml x kg(-1) x min(-1). Two groups were formed using a median split based on VO2max. For the high and low VO2max groups, VO2max was 65.7 +/- 3.0 and 52.4 +/- 1.8 ml x kg(-1) x min(-1) respectively. The limits of agreement (95%) for test-retest reproducibility for the VO2 attained during the 800-m trials were +/- 3.5 ml x kg(-1) x min(-1) for a VO2peak of 50.6 ml x kg(-1) x min(-1) (the mean VO2peak for the low VO2max group) and +/- 2.3 ml x kg(-1) x min(-1) for a VO2peak of 59.0 ml x kg(-1) x min(-1) (the mean VO2peak for the high VO2max group), with a bias in VO2peak between the 800-m runs (i.e. the mean difference) of 1.2 ml x kg(-1) x min(-1). The VO2peak for the 800-m runs was 54.8 +/- 4.9 ml x kg(-1) x min(-1) for all 15 runners. For the high and low VO2max groups, VO2peak was 59.0 +/- 3.3 ml x kg(-1) x min(-1) (i.e. 90% VO2max) and 50.6 +/- 2.0 ml x kg(-1) x min(-1) (i.e. 97% VO2max) respectively. The negative relationship (-0.77) between VO2max and % VO2max attained for all 15 runners was significant (P = 0.001). These results demonstrate that (i) reproducibility is good and (ii) that VO2max is related to the %VO2max achieved, with participants with a higher VO2max achieving a lower %VO2max in an 800-m trial on a treadmill.