Nordic hamstring evidence

Hamstring strains often happen when a runner’s back-thigh muscles are lengthening under load, and a new 2026 study says nine weeks of Nordic hamstring training changed that mechanics in measurable ways. (sciencedirect.com) The Nordic hamstring exercise is the partner drill where an athlete kneels and slowly resists a forward fall, forcing the hamstrings to work while they lengthen. Researchers from the University of Queensland, the University of Southern Queensland, and Stanford studied how that drill changed the biceps femoris long head, the hamstring muscle most often injured in sprinting. (eurekalert.org) The new paper was published March 19, 2026 in the *Journal of Sport and Health Science* and tracked changes during a supervised nine-week program. The team used ultrasound to measure muscle fascicles, motion capture to estimate whole muscle-tendon length, and prior sarcomere measurements to estimate what happened at the microscopic level. (pubmed.ncbi.nlm.nih.gov) The key finding was mechanical, not just anatomical: after training, muscle fibers worked at longer overall lengths while the sarcomeres — the tiny force-producing units inside them — stayed closer to their optimal range instead of being pushed toward overstretch. The authors said that pattern helps explain why eccentric training lowers injury risk in sprinting sports. (eurekalert.org) That explanation builds on a 2024 paper from the same group, which reported that nine weeks of Nordic hamstring training increased fascicle length by 19% in the central region and 33% in the distal region of the biceps femoris long head. The same study found serial sarcomere number rose 25% centrally and 49% distally, muscle volume increased 8%, and knee-flexion strength increased 40%. (pmc.ncbi.nlm.nih.gov) Those numbers matter because hamstring injuries are common in sports built on sprinting and acceleration. A Stanford summary of the earlier work said they account for about 10% of injuries in field-based sports, while a 2024 umbrella review found Nordic hamstring interventions cut hamstring injuries by as much as 51% across the literature it examined. (humanperformance.stanford.edu) (pmc.ncbi.nlm.nih.gov) The new study does not show injury counts in a season-long team trial; it shows a mechanism in the lab that fits the injury-prevention results reported in earlier reviews. The participant group in the 2024 structural study was also small, with 12 people completing the nine-week supervised program. (pmc.ncbi.nlm.nih.gov 1) (pmc.ncbi.nlm.nih.gov 2) The same 2024 paper found some of the gains started to fade after three weeks without training. Fascicle length fell 12% in the central region and 16% in the distal region after detraining, alongside reductions in serial sarcomere number. (pmc.ncbi.nlm.nih.gov) So the picture from these studies is narrower and clearer than a generic “stronger hamstrings” claim: nine weeks of Nordic work appears to remodel the muscle so it can tolerate longer lengths without overstraining its smallest working parts. That gives coaches and athletes a biological reason, not just an outcome statistic, for keeping the exercise in training plans. (sciencedirect.com) (eurekalert.org)