Can in-season Nordic hamstring exercise microdosing retain eccentric hamstring strength?

Exercise microdosing has been adopted in sports to maintain physical capacities throughout the competitive season. This study aimed to determine whether in-season Nordic hamstring exercise (NHE) microdosing could retain eccentric hamstring strength after a preseason NHE program. Thirty-four athletes completed a 5-week preseason program including a typical-volume NHE protocol (up to 60 repetitions per week). Athletes were then randomized to either a control group, which performed no NHE during the in-season period, or a microdose group, which performed one set of 6 NHE repetitions per week. Eccentric hamstring strength was assessed at baseline, immediately after preseason, and after 5 and 10 weeks of the in-season period. From baseline to the end of preseason, athletes experienced a mean increase of 9.5% (95% CI, 5.3 to 14.3%) in eccentric hamstring strength (microdose: 317±82 N to 346±82 N; control: 292±82 N to 321±82 N). After 5 weeks of the in-season period, strength values returned to baseline levels (microdose: 324±83 N; control: 289±83 N) and remained stable through the 10th in-season week (microdose: 330±83 N; control: 290±84 N). No significant between-group differences were observed. In conclusion, this microdose strategy was insufficient to retain eccentric hamstring strength after the preseason training period.