Muscle Activity and Power Output Between Stationary and Outdoor Cycling
Creators: name: Joerger, Jared 
Publisher: name: University of Nevada, Las Vegas
Year: 2016

description: The purpose of this study is to compare lower extremity muscle activity and power output during cycling outdoors overground and cycling on a stationary bike trainer at different self-perceived intensity levels. Recreational and competitive cyclists and triathletes, eight male (48.6±8.7 years, 178.9±7.8 cm, 87.1±8.3kg) and three female (40.3±6.8 years, 158±1 cm, 59.6±9.3 kg), signed institutionally approved informed consents and participated in this study. Power data were collected using power instrumented bicycle pedals (PowerTap, Madison, WI) attached to the cyclist's bicycle. Muscle activity was recorded using wireless electromyography (Delsys, Inc., Natick, MA) sampling at 1926Hz. Participants were tested for maximum voluntary isometric contraction (MVIC) for all muscles tested: the rectus femoris, biceps femoris, vastus lateralis, gluteus maximus, and gastrocnemius. MVIC data were used to normalize electromyography (EMG) from each cycling condition. Participants were instructed to complete four-minute cycling trials at different self-perceived intensity levels (RPE 11, RPE 13, RPE 15) during overground and stationary cycling. For overground cycling, participants rode around a pre-marked, 400-m loop. For stationary cycling, participant's bicycles were fixed to a stationary bike trainer. During each condition, participants continuously pedaled for two minutes, then were instructed to coast for two seconds. They then resumed cycling for another two minutes.
EMG data were processed by correcting for any zero offset, full-wave rectifying the data, and normalizing to MVIC. The two second pause was visually identified, then a twenty second average for each muscle was calculated following the pause. Power data were also visually inspected, and the two second pause was identified. A twenty second average was calculated for power output following the pause. A 2 (stationary versus overground) x 3 (RPE) repeated measures ANOVA was run for each dependent variable (?=0.05). The statistical analysis was completed using SPSS statistical software (v24). 
Power output did not differ between overground and stationary, regardless of intensity (p>0.05). However, power output increased as intensity increased, regardless of mode (p<0.05). There was no significant difference between overground and stationary cycling for the rectus femoris, regardless of intensity (p>0.05). Muscle activity significantly increased as RPE level increased, regardless of mode (p<0.05). Biceps femoris muscle activity was influenced by the interaction of mode and intensity. Using post hoc testing, it was determined that muscle activity increased as intensity increased during stationary cycling (p<0.05). However, there was no significant difference in muscle activity between modes of cycling and no change in activity as RPE level increased (p>0.05). There was no significant difference between overground and stationary cycling for vastus lateralis muscle activity (p>0.05). Muscle activity increased as RPE level increased, regardless of mode (p<0.05). Gluteus maximus activity was significantly greater during overground cycling than stationary cycling, regardless of intensity (p<0.05). Muscle activity also increased as self-selected intensity increased, regardless of mode (p<0.05). There was no significant difference between mode of cycling for gastrocnemius (p>0.05). Muscle activity increased as RPE level increased (p<0.05). The results of this study show that hip extensor and knee flexor muscles have unique responses between submaximal overground and stationary cycling.