The highly repetitive movement makes cycling prone to injuries. Research showed the importance of effective muscle recruitment and kinematics in preventing these injuries. However, little evidence exists on how fatigue influences these factors, mainly due to a lack of possibilities to measure kinematics outside the laboratory. Advances in sensor technology allow for mobile measurement of neuromuscular control and kinematics to quantify the fatiguing effects of sport-specific duration and setting in cycling.
PURPOSE: Quantifying the effects of sport-specific fatigue on neuromuscular activation and lower limb kinematics in road cycling.
METHODS: 6 Elite female cyclists (Age: 22.8 +/- 2.2. Height: 169 +/- 7 cm. Weight: 57.3 +/- 2.9 kg. Power > 4,5 W/kg) performed a 205 altitude meters hill climb (avg. incl. 8%) twice, interspersed by a flat 1 hour cycle at mild intensity. Bilateral surface electromyography (EMG) of the m. vastus medialis (VM) and m. vastus lateralis (VL) was combined with wireless inertial magnetic units (IMU’s) at the lower and upper leg, sacrum and sternum to measure kinematics. A paired Wilcoxon signed-rank test was used to compare EMG (VL:VM activation ratio) and IMU data (3D knee and hip ROM) during the final minute of the first (UH1) and second, fatigued uphill ride (UH2).
RESULTS: Mean VL:VM ratio showed a non-significant increase of the right(R) (UH1: 1.19 +/- 0.08; UH2: 1.35 +/- 0.22; p<0.06) and left(L) leg (UH1: 1.20 +/- 0.08; UH2: 1.25 +/- 0.10; p<0.34). Sagittal-plane knee angles showed no significant difference between UH1 and UH2, though mean hip angles did show an increase in both R (UH1: 68.0 +/- 3.10, UH2: 73.7 +/- 3.20 p<0.031) and L (UH1: 65.2 +/- 4.20, UH2: 72.5 +/- 4.40; p<0.031).
DISCUSSION: In this small population significant changes were seen in hip angle as a consequence of fatigue. Non-significant increases in VL/VM ratio were observed. Previous research in patella femoral pain syndrome (PFPS) showed a higher VL:VM ratio (1.78) in symptomatic than in healthy subjects (1.17). This might be an indicator of overuse after repetitive exposure. More subject are needed to test this hypothesis.
CONCLUSIONS: This study showed the possibility of continuously measuring muscle activation and kinematics in the sport-specific setting and objectified the effects of fatigue during uphill cycling.