Exploring Single-Leg Jump Testing as an Assessment of Functional Capacity in Achilles Tendinopathy: A Cross-Sectional Study.

Introduction: This study explored single-leg jump testing as a quantitative measure of functional capacity by analyzing jump performance metrics (JPM) and the associated onset of muscle activity in Achilles tendinopathy (AT) participants compared to healthy controls (CON). Methods: Twenty-four males participating in running sports (12 AT, 12 CON) performed the testing battery on a force plate, including vertical jumps, reactive jumps (RJs), and drop jumps. Analyzed JPM included ground contact time, flight time, peak force during jumps and landings, jump height, modified reactive strength index, and net impulse. Additionally, the limb-symmetry index was compared between groups along with the onset of seven lower limb muscles measured by surface electromyography. Results: Multivariate comparisons showed no significant differences in JPM or limb-symmetry index between AT and CON participants. Solely, the AT group presented an earlier onset of tibialis anterior during RJs (p=0.005). Discussion: In conclusion, single-leg jump testing in the targeted population indicated no generalized changes in overall functional capacity or onset of muscle activity, except in one jump for one specific muscle. However, the descriptively observed increased variability might suggest heterogeneous coping strategies in the presence of AT, highlighting the need for individualized assessments to detect performance deficits.