Examining the effect of verbal feedback vs. real-time software feedback on kinetic and kinematic metrics of the Nordic hamstring exercise

Purpose

A wealth of research exists for the Nordic hamstring exercise and several devices provide real-time feedback on torque profiling. However, none currently offer feedback on technique execution. This study investigated the effect of verbal and software feedback on Nordic exercise kinetic and kinematic metrics.

Methods

24 recreational participants completed two sets of three bilateral repetitions on a hamstring testing device. In a crossover design, one set was performed with verbal feedback, while the other set used software-based feedback. Hamstring strain injury risk metrics (peak torque, break-torque angle, and bilateral limb percentage difference) and exercise technique metrics (relative trunk-to-thigh angle and angular velocity of the knee) were recorded for analysis.

Results

The feedback type significantly affected eccentric knee flexor peak torque, by a mean decrease of 7.1 Nm when performed with software feedback (Cohen’s d = 0.238, p < 0.01). Altering feedback had no significant effect on bilateral limb difference percentage (Cohen’s d = 0.068, p = 0.578) or break-torque angle (Cohen’s d = 0.159, p = 0.115). Software feedback significantly decreased the mean of both the relative-trunk-to-thigh angle at peak torque by 5.7° (Cohen’s d = 0.514, p < 0.01) and the angular velocity of the knee at peak torque by 8.7 deg·s−1.

Conclusions

An integrated software feedback system significantly improves acute Nordic exercise technique, benefitting individuals initially exhibiting poorer technique the most.