Abstract
This study investigated whether and how ultralow-volume Nordic hamstring exercise (NHE) training can maintain neuromuscular adaptations achieved through initial moderate-volume training. Specifically, we examined changes in eccentric knee flexor strength, fascicle length, and stiffness of the biceps femoris long head (BFlh) across different training volumes. Forty-five resistance-trained males were randomly assigned to three groups: low-volume, ultralow-volume, and control (n = 15 per group). Training groups performed standardized moderate-volume NHE training (48 repetitions/week) for 2 weeks, followed by low-volume (eight repetitions/week) or ultralow-volume (four repetitions/week) training for 8 weeks. Eccentric knee flexor strength, BFlh fascicle length, and BFlh stiffness assessed via shear wave elastography were measured at four time points: weeks 0 (baseline), 2, 6, and 10. In both training groups, eccentric knee flexor strength increased significantly during the initial 2 weeks and continued to increase through week 6 despite the reduction in training volume, with no further increases beyond week 6. BFlh fascicle length increased, and stiffness decreased significantly after 2 weeks of moderate-volume training, and these adaptations were maintained throughout the subsequent 8 weeks. No significant differences were found between the two training groups for any parameter. The control group showed no significant changes. These findings indicate that neuromuscular adaptations induced by 2 weeks of moderate-volume NHE training can be effectively maintained with as little as four repetitions per week of supramaximal NHE training, providing practical implications for in-season training programming.