Examining the Effects of Body Weight Support and Speed on Physiological Measures and Lower Leg Muscular Activity

摘要

The purpose of this study was to determine if body weight support or speed influences specific physiological and biomechanical parameters while running at a preferred pace, or variations of preferred pace. Nine participants (age: 28.56 ± 7.88 years, height: 1.68 ± 0.08 cm, mass: 65.70 ± 7.64 kg) who were running a minimum of 10 miles per week (14.67 ± 4.92 miles) were recruited for participation. Participants were asked to sign an institutionally approved informed consent form upon arrival to the lab. After determining preferred running speed at each body weight support condition (no support, 10%, and 20% support), participants were instrumented with four Delsys EMG leads, a PCB one-dimensional accelerometer, and a K4B2 portable metabolic gas analysis system to measure muscle activity, tibial acceleration, and metabolic variables at various points throughout each running condition. Muscle activity was recorded for the rectus femoris, semitendinosus, tibialis anterior, and medial gastrocnemius muscles. Participants were asked to run a total of nine conditions, running with no body weight support, 10% support, and 20% support at a preferred running pace, as well as +10% and -10% of that preferred speed. Average muscle activity, average tibial acceleration, and average VO2 and VCO2 values were determined for each condition. None of the dependent variables were influenced by the interaction of speed and body weight support (pu3e0.05). EMG of the four lower extremity muscles was not influenced independently by body weight support (pu3e0.05) or speed (pu3e0.05). VO2 was influenced by body weight support (pu3c0.001), reporting VO2 during running at 0% support was significantly higher than VO2 at both 10% body weight support (pu3c0.05) and 20% body weight support (pu3c0.05). Tibial acceleration was not influenced by body weight support (pu3e0.05) but was influenced by speed (pu3c0.05). Specifically, tibial acceleration was significantly higher during the +10% of preferred speed condition compared with both the preferred speed condition (pu3c0.05) and the -10% of preferred speed condition (pu3c0.05). It is concluded that oxygen consumption was affected by both body weight support and speed; yet, lower extremity muscle activity was not. It should be understood that although it may be possible to achieve similar levels of muscle activation while running at 10% and 20% support, the metabolic demand is continually less and less as body weight support is added.