Jeremy Witchalls

Use of a tibial accelerometer to measure ground reaction force in running: A reliability and validity comparison with force plates

OBJECTIVES The use of microsensor technologies to conduct research and implement interventions in sports and exercise medicine has increased recently. The objective of this paper was to determine the validity and reliability of the ViPerform as a measure of load compared to vertical ground reaction force (GRF) as measured by force plates. DESIGN Absolute reliability assessment, with concurrent validity. METHODS 10 professional triathletes ran 10 trials over force plates with the ViPerform mounted on the mid portion of the medial tibia. Calculated vertical ground reaction force data from the ViPerform was matched to the same stride on the force plate. Bland-Altman (BA) plot of comparative measure of agreement was used to assess the relationship between the calculated load from the accelerometer and the force plates. Reliability was calculated by intra-class correlation coefficients (ICC) with 95% confidence intervals. RESULTS BA plot indicates minimal agreement between the measures derived from the force plate and ViPerform, with variation at an individual participant plot level. Reliability was excellent (ICC=0.877; 95% CI=0.825-0.917) in calculating the same vertical GRF in a repeated trial. Standard error of measure (SEM) equalled 99.83 units (95% CI=82.10-119.09), which, in turn, gave a minimum detectable change (MDC) value of 276.72 units (95% CI=227.32-330.07). CONCLUSIONS The ViPerform does not calculate absolute values of vertical GRF similar to those measured by a force plate. It does provide a valid and reliable calculation of an athletes lower limb load at constant velocity.

Predicting individual risk for medial tibial stress syndrome in navy recruits

OBJECTIVES Quantifying individual risk for medial tibial stress syndrome (MTSS) is valuable due to the high prevalence, substantial financial and service costs, and lengthy recovery time of the condition. Identification of those at risk is a key first step in prevention of the condition. This study aimed to test a suite of best evidence risk factors in a cohort of Navy recruits and to develop a predictive model for individuals at risk of MTSS. DESIGN Prospective cohort study of Navy recruits undergoing initial training METHODS: A prospective cohort design, this study screened recruits by assessing gender, MTSS history, years of running experience, orthotic use, BMI, navicular drop, ankle plantarflexion and hip external rotation at the beginning of basic training. Follow-up was conducted at completion of training (11 weeks). RESULTS Volunteers included 123 recruits (28 females and 95 males). Thirty developed MTSS (19 males and 11 females). Stepwise logistic regression of one half of the data produced a significant model (p<0.001), comprising female gender (OR 4.4, 95% CI 1.0, 18.9, p=0.05), MTSS history (OR 18.3, 95% CI 3.6, 91.5, p<0.01) and increased hip ER (OR 1.1 per degree, 95% CI 1.0, 1.202, p=0.05). Findings validated with the other half of the cohort and receiver operating characteristic curve analysis showed the model had 82% sensitivity and 84% specificity. CONCLUSIONS This predictive model provides military institutions, clinicians and instructors with a strong and accurate calculator for predicting an individual recruits risk of MTSS.

Military human performance optimization and injury prevention: Strategies for the 21st century warfighter

This special issue of the Journal of Science and Medicine in Sport s dedicated to the topic of optimizing physical performance and educing musculoskeletal injury. Effective military training should ncrease physical performance capabilities without incurring high ates of injury. Training injuries are not a badge of honor but rather ndicate less than optimal training programs. Better understanding f all aspects contributing to the training ecosystem, including facors such as, musculoskeletal physiology, responses to a training timulus and the influences of rest, nutrition, and personal health abits, provide a scientific basis for the design of training programs hat will result in soldiers with greater job-specific capabilities.1–3 etter understanding of injury risk factors contributes to the design f programs that should reduce training injuries even as they mprove in effectiveness.1–3 Over the years, military training epiemiology has identified aspects of how injury risk is heightened, uch as running in formation with the shortest individuals overtriding in the rear, performing training runs in boots, immediately tarting new training with high workloads, etc.1,2 As injury risks ave been reduced, additional risk factors have been exposed and otentially can also be reduced. The articles in this issue identify ome of the latest findings pertinent to military physical training. hese findings are relevant well beyond the military, with applicaions in many other occupationally related physical performance rograms and to athletic training. This special issue on Military Human Performance Optimizaion/Injury Prevention contains 18 manuscripts from 5 different rganizations dedicated toward studying biomedical research soluions to benefit military physical performance and readiness: the euromuscular Research Laboratory/Warrior Human Performance esearch Center (NMRL/WHPRC) at the University of Pittsburgh, he Military Performance Division at the U.S. Army Research Instiute of Environmental Medicine (USARIEM), the Injury Prevention ivision at the U.S. Army Public Health Center (APHC), the Division f Applied Physiology, Army Personnel Research Capability (APRC), ritish Ministry of Defence, and the Land Division, Australian efence Science and Technology (DST) Group. These manuscripts over a range of topics, including: development of military physical mployment standard assessments, military injury epidemiology nd associated risk factors, and physiological, neuromuscular, and ormonal adaptations to physical training and load carriage. The cientific findings of these manuscripts add to the knowledge base ith regard how best to leverage and translate human performance