Eccentric Braking in the Squat with Varied Inertial Loads: a Case Study with 2D Analysis

Eccentric braking plays a key role in flywheel exercises, contributing to strength gains and neuromuscular control. This case study examined how different inertial loads (0.035, 0.050, and 0.075 kg·m²) affect eccentric braking during the squat, using two-dimensional kinematic analysis. The aim of the study was to examine eccentric overload during the squat exercise under different inertial loads. One participant performed three sets of eight repetitions per load, with two additional reps for flywheel acceleration. Movements were recorded laterally with a digital camera and analysed using Tracker software, referencing the hip joint. Vertical coordinates (Y-axis) were smoothed using a five-point moving average. Velocity and acceleration were derived from the first and second derivatives, respectively. Negative acceleration peaks at the end of the downward motion identified the eccentric braking phase. At 0.035 kg·m², a larger range of motion and higher negative acceleration peaks were found, but with irregular patterns, indicating reduced motor control. The intermediate load (0.050 kg·m²) produced similarly high peaks with greater consistency across cycles. At 0.075 kg·m², movement was more constrained, with slower execution and smaller peaks, but with greater stability and control, suggesting refined motor coordination. These findings demonstrate that increasing inertial load directly influences eccentric braking: lighter loads yield high eccentric force but less control; intermediate loads balance force and stability; heavier loads reduce peak force yet enhance control. This underscores the importance of progressive load selection in flywheel training to match the stimulus to specific training goals.