Physiological and Biomechanical Responses of Highly Trained Distance Runners to Lower-Body Positive Pressure Treadmill Running

Barnes and Janecke Sports Medicine - Open Physiological and Biomechanical Responses of Highly Trained Distance Runners to Lower-Body Positive Pressure Treadmill Running Kyle R. Barnes 0 Jessica N. Janecke 1 0 Department of Movement Science, Grand Valley State University , 1 Campus Drive, Allendale, MI 49401 , USA 1 Office of Undergraduate Research and Scholarship, Grand Valley State University , 1 Campus Drive, Allendale, MI 49401 , USA Background: As a way to train at faster running speeds, add training volume, prevent injury, or rehabilitate after an injury, lower-body positive pressure treadmills (LBPPT) have become increasingly commonplace among athletes. However, there are conflicting evidence and a paucity of data describing the physiological and biomechanical responses to LBPPT running in highly trained or elite caliber runners at the running speeds they habitually train at, which are considerably faster than those of recreational runners. Furthermore, data is lacking regarding female runners' responses to LBPPT running. Therefore, this study was designed to evaluate the physiological and biomechanical responses to LBPPT running in highly trained male and female distance runners. Methods: Fifteen highly trained distance runners (seven male; eight female) completed a single running test composed of 4 × 9-min interval series at fixed percentages of body weight ranging from 0 to 30% body weight support (BWS) in 10% increments on LBPPT. The first interval was always conducted at 0% BWS; thereafter, intervals at 10, 20, and 30% BWS were conducted in random order. Each interval consisted of three stages of 3 min each, at velocities of 14.5, 16.1, and 17.7 km·h−1 for men and 12.9, 14.5, and 16.1 km·h−1 for women. Expired gases, ventilation, breathing frequency, heart rate (HR), rating of perceived exertion (RPE), and stride characteristics were measured during each running speed and BWS. Results: Male and female runners had similar physiological and biomechanical responses to running on LBPPT. Increasing BWS increased stride length (p < 0.02) and flight duration (p < 0.01) and decreased stride rate (p < 0.01) and contact time (p < 0.01) in small-large magnitudes. There was a large attenuation of oxygen consumption (VO2) relative to BWS (p < 0.001), while there were trivial-moderate reductions in respiratory exchange ratio, minute ventilation, and respiratory frequency (p > 0.05), and small-large effects on HR and RPE (p < 0.01). There were trivial-small differences in VE, respiratory frequency, HR, and RPE for a given VO2 across various BWS (p > 0.05). Conclusions: The results indicate the male and female distance runners have similar physiological and biomechanical responses to LBPPT running. Overall, the biomechanical changes during LBPPT running all contributed to less metabolic cost and corresponding physiological changes. AlterG; Lower-body positive pressure; Body weight support; Anti-gravity; Running; Stride characteristics; Physiological characteristics; Metabolic demand; Oxygen demand; Oxygen cost Key Points Well-trained male and female distance runners have similar physiological and biomechanical responses while running with body weight support on a lowerbody positive pressure treadmill. When considering the global unweighing effects on stride parameters during running, its major influence was the large increase in flight time, which contrasted the disproportional decrease in contact time resulting in overall longer stride length and reduction in stride rate. There was a disproportionate decrease in oxygen consumption relative to body weight support which led to an attenuation of heart rate and rating of perceived exertion and, to a lesser degree, respiratory exchange ratio, minute ventilation, and respiratory frequency between each level of body weight support and running speed. Background Body weight support and running velocity both affect the physiological and biomechanical responses of human running [ 1 ]. Previous studies show that when running at normal body weight, metabolic demand increases with velocity [ 2, 3 ]. The greater metabolic demand of faster running speeds has been attributed to increases in stride frequency, increases in mechanical power, and generation of greater ground reaction forces over shorter periods of ground contact [ 2, 4, 5 ]. Coaches and athletes have used the increased metabolic demand associated with faster running velocities as a means of enhancing aerobic capacity and running performance [ 6, 7 ]. However, running at fast velocities cannot be sustained over extended durations and greatly increases the risk of overuse and orthopedic injury [ 8 ]. Thus, as a way to train at faster running speeds, to add training volume, or when people may not be able to run safely at their full body weight after orthopedic injury and/or surgery, lower-body positive pressure treadmills (LBPPT), such as the AlterG Anti-Gravity Treadmill® (AlterG, Inc., Menlo Park (...truncated)