Nordic Hamstring Exercise training induces improved lower-limb swing phase mechanics and sustained strength preservation in sprinters

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Nordic Hamstring Exercise (NHE) training improves eccentric hamstring strength and sprint performance. However, detraining causes rapid reductions of achieved adaptations. Furthermore, the transfer of improved hamstring capacity to swing phase mechanics of sprints is unknown. This longitudinal study aimed (1) to quantify NHE-induced adaptations by camera- based isokinetic assessments and sprint analyses, (2) to relate the magnitude of adaptations to the participants’ initial performance level, (3) to investigate the transferability to sprints, and (4) to determine strength preservations after three months. Twelve sprinters (21 y, 1.81 m, 74 kg) were analysed throughout 22 weeks. They performed maximal sprints and eccentric knee flexor and concentric knee extensor tests before and after a 4-week NHE training. Sprints and isokinetic tests were captured by ten and four high-speed cameras. The dynamic control ratio at the equilibrium point (DCRe) evaluated thigh muscle balance. High- intensity NHE training elicited significant improvements of hamstring function (p range: <0.001 to 0.011, d range: 0.44 to 1.14), thigh muscle balance (p<0.001, d range: 0.80 to 1.08) and hamstring-related parameters of swing phase mechanics (p range: <0.001 to 0.022, d range: 0.12 to 0.57). Sprint velocity moderately increased (+1.4%, p<0.001, d=0.26). Adaptations of Hecc hamstring function and DCRe thigh muscle balance revealed moderate to strong transfers to improved sprint mechanics (, p range: <0.001 to 0.048, R2 range: 34% to 83%). The weakest participants demonstrated the highest adaptations of isokinetic parameters (p range: 0.003 to ≤0.023, R2 range: 42% to 62%), whereas sprint mechanics showed no effect of initial performance level. Three months after the intervention, hamstring function (+6% to +14%) and thigh muscle balance (+8% to +10%) remained significantly enhanced (p<0.001, ƞp2 range: 0.529 to 0.621). High-intensity NHE training induced sustained, improved hamstring function of sprinters, which can be transferred to swing phase mechanics of maximal sprints. The initial performance level, NHE training procedures and periodisation should be considered to optimize adaptations.
OriginalspracheEnglisch
ZeitschriftScandinavian journal of medicine & science in sports
Seitenumfang13
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PublikationsstatusElektronische Veröffentlichung vor Drucklegung. - 20.12.2020

ID: 5535423

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