Alena M. Grabowski and Rodger Kram
The biomechanical and metabolic demands of human running are distinctly affected by velocity and body weight. As runners increase velocity, ground reaction forces (GRF) increase, which may increase the risk of an overuse injury, and more metabolic power is required to produce greater rates of muscular force generation. Running with weight support attenuates GRFs, but demands less metabolic power than normal weight running. We used a recently developed device (G-trainer) that uses positive air pressure around the lower body to support body weight during treadmill running. Our scientific goal was to quantify the separate and combined effects of running velocity and weight support on GRFs and metabolic power. After obtaining this basic data set, we identified velocity and weight support combinations that resulted in different peak GRFs, yet demanded the same metabolic power. Ideal combinations of velocity and weight could potentially reduce biomechanical risks by attenuating peak GRFs while maintaining aerobic and neuromuscular benefits. Indeed, we found many combinations that decreased peak vertical GRFs yet demanded the same metabolic power as running slower at normal weight. This approach of manipulating velocity and weight during running may prove effective as a training and/or rehabilitation strategy.
James E. Peterman, Kalee L. Morris, Rodger Kram and William C. Byrnes
Background: In laboratory settings, cycling workstations improve cardiometabolic risk factors. Our purpose was to quantify risk factors following a cycling intervention in the workplace. Methods: Twenty-one office workers who sat at work ≥6 hours per day underwent baseline physiological measurements (resting blood pressure, blood lipid profile, maximum oxygen consumption [
Paolo Taboga, Alena M. Grabowski, Pietro Enrico di Prampero and Rodger Kram
In the 2012 Paralympic 100 m and 200 m finals, 86% of athletes with a unilateral amputation placed their unaffected leg on the front starting block. Can this preference be explained biomechanically? We measured the biomechanical effects of starting block configuration for seven nonamputee sprinters and nine athletes with a unilateral amputation. Each subject performed six starts, alternating between their usual and unusual starting block configurations. When sprinters with an amputation placed their unaffected leg on the front block, they developed 6% greater mean resultant combined force compared with the opposite configuration (1.38 ± 0.06 vs 1.30 ± 0.11 BW, P = .015). However, because of a more vertical push angle, horizontal acceleration performance was equivalent between starting block configurations. We then used force data from each sprinter with an amputation to calculate the hypothetical starting mechanics for a virtual nonamputee (two unaffected legs) and a virtual bilateral amputee (two affected legs). Accelerations of virtual bilateral amputees were 15% slower compared with athletes with a unilateral amputation, which in turn were 11% slower than virtual nonamputees. Our biomechanical data do not explain the starting block configuration preference but they do explain the starting performance differences observed between nonamputee athletes and those with leg amputations.
Peter R. Cavanagh, Gary C. Andrew, Rodger Kram, Mary M. Rodgers, David J. Sanderson and Ewald M. Hennig
A comprehensive biomechanical profile for the evaluation of elite distance runners is outlined. The profile includes the following sections: (a) structural assessment, (b) movement analysis, (c) plantar force and pressure, and (d) selected metabolic measurements. For each of these sections the methodology is described, examples of results from two elite distance runners evaluated are presented and, where appropriate, recommendations for performance improvement and/or injury prevention are made. The concluding discussion addresses a number of philosophical issues related to the biomechanical study of elite athletes and makes some' recommendations for farther development of programs of this nature.