Acute Effects of Cycling-Induced Fatigue on Walking Gait in Endurance Athletes

Previous studies have shown that the transition from cycling to running is less biomechanically efficient than a stand-alone run, which makes triathletes more susceptible to injury and inhibits performance. While several studies have examined the effects of cycling on running gait, little is known about its impact on walking gait. PURPOSE: The purpose of this study was to examine any changes in muscle recruitment and hip and knee kinetics and kinematics during walking of endurance athletes under cycling-induced fatigue conditions. METHODS: Six college-aged women performed two conditions walking across force plates, heel strike to heel strike, with their dominant leg. The first condition was without fatigue, and the next was after a cycling fatigue protocol where they performed 10 minutes of high-intensity cardio on a stationary bicycle. Fatigue indices included a minimum of 80% heart rate max and a subjective measure on the RPE Borg scale. Hip and knee kinematics were measured using flexion and extension moment using a 12-camera motion analysis system with Cortex software (Motion Analysis Corp., Santa Rosa, CA) and 32 retro-reflective markers. Kinetic measures examined braking and propulsion forces using force plates (Accugait, AMTI, MA). Muscle recruitment was measured using wireless EMG sensors (Delsys, MA) placed on the tibialis anterior, gastrocnemius, vastus lateralis, and biceps femoris of the dominant leg. RESULTS: Kinematic results showed a statistically significant increase in hip and knee flexion after fatigue conditions were met in all participants for the first 30% of the cycle (early-mid stance). No significant difference was found during the swing phase. There were no significant differences in kinetic measures between the two groups. EMG results demonstrated a decreased activation of the biceps femoris muscle during the fatigue trial. CONCLUSION: Walking biomechanics may be influenced by cycling fatigue, but not to the extent of running biomechanics.