The effect of fatigue on body kinematics during simulated flat water kayak

Abstract

Flat-water kayak requires both technical skills and muscle strength. Previous studies con- ducted during simulated kayaking suggest that different kinematic variables (joints range of motion [RoM], symmetry, paddle position) are related to performance improvements [1,2] and may distinguish athletes of different competitive levels. On the other hand, muscle fatigue negatively affects both upper and lower limbs performance [3], but its effect on kayaking tech- nique and body arrangement has not been analyzed yet. In this study, we examined changes of 3D kinematics through a simulated 500-meter kayak sprint. Ten athletes (7 M, 3 F, mean age 17±2 y) performed on a kayak ergometer: 1) an incremental test (INCR) to detect peak oxygen uptake (O2peak); 2) a 500-meter sprint trial (TT). During TT, besides collecting cardiometabolic response to exercise and blood lactate concentration ([Lapeak]), a motion capture system sam- pled the 3D coordinates of 40 cutaneous markers. For each athlete, joints RoMs (trunk, pel- vis, lower and upper limbs) were obtained together with symmetry indices. Stroke frequency was computed from the wrist landmarks trajectory. To assess the effect of fatigue on kinemat- ics, data obtained at the beginning of TT (11th-20th rowing cycles) were compared with that obtained at the end (last 10 cycles). During INCR, O2peak was 3.36 L/min. TT lasted 130.1±9.2 s, and paddle frequency was 1.1±0.2 s-1. During TT, in all subjects O2 value was higher than 90% of O2peak, whereas [Lapeak] was 10.6±3.1 mM, thus indicating a large contribution of both aerobic and anaerobic energy systems. Fatigue influenced joints RoM, with an increment in lower limbs joints (significant hip rotation, effect size [ES] 0.60), and a decrement in domi- nant side shoulder (rotation and adduction; ES 0.58). Trunk inclination also increased (ES 0.63). The first part of TT was performed with a higher shoulder rotation asymmetry (larger domi- nant limb RoM) than the last part. Results suggest that fatigue affects kinematic variables relat- ed to technical skills, where increased trunk and lower limb RoMs may compensate reduced upper limb movements and symmetry. If confirmed, these data can provide useful information to optimize training programs.