The Effects of Bicycle Frame Geometry on Muscle Activation and Power During a Wingate Anaerobic Test

The purpose of this study was to compare the effects of bicycle seat tube angles (STA) of (72° and 82°) on power production and EMG of the vastus laeralis (VL), vastus medialis (VM), semimembranous (SM), biceps femoris (BF) during a Wingate test (WAT). Twelve experienced cyclists performed a WAT at each STA. Repeated measures ANOVA was used to identify differences in muscular activation by STA. EMG variables were normalized to isometric maximum voluntary contraction (MVC). Paired t-tests were used to test the effects of STA on: peak power, average power, minimum power and percent power drop. Results indicated BF activation was significantly lower at STA 82° (482.9 ± 166.6 %MVC·s) compared to STA 72° (712.6 ± 265.6 %MVC·s). There were no differences in the power variables between STAs. The primary finding was that increasing the STA from 72° to 82° enabled triathletes’ to maintain power production, while significantly reducing the muscular activation of the biceps femoris muscle.

Key Points

• Road cyclists claim that bicycle seat tube angles between 72° and 76° are most effective for optimal performance in racing.
• Triathletes typically use seat tube angles greater than 76°. It is thought that a seat tube angle greater than 76° facilitates a smoother bike to run transition in the triathlon.
• Increasing the seat tube angle from 72 to 82 enabled triathletes’ to maintain power production, while significantly reducing the muscular activation of the biceps femoris muscle.
• Reduced hamstring muscular activation in the triathlon frame (82 seat tube angle) may serve to reduce hamstring tightness following the bike phase of the triathlon, allowing the runner to use a longer stride length.

Key words: Cycling, anaerobic power, triathlon, efficiency, EMG