BACKGROUNDː Hamstring Strain Injuries (HSI) are among the most common injuries in field based team sports with a high speed running component. The implementation of the Nordic Hamstring Exercise (NHE) is a well documented method of improving eccentric hamstring strength to mitigate the risk of HSI occurance. Sprint training is specific to the injury mechanism and is thought to activate the hamstrings through maximal eccentric contractions. The purpose of this study was to compare the effects of sprint training and the NHE on eccentric hamstring strength and sprint performance. METHODSː Twenty-eight participants (Mean ± SD age = 16.21 ± 1.34 years; height = 1.75m ± 0.10m; body mass = 68.5kg ± 12.1kg) completed an eccentric hamstring strength assessment and 40m sprint to assess acceleration and maximum speed. Participants were randomly allocated to either a NHE training or sprint training group. Two sessions per week for four-weeks of training was performed with baseline testing procedures repeated in the week following the intervention. Perceptions of soreness were recorded following the warmup in each training session. RESULTSː Both the NHE (effect size = 0.39, p < 0.05) and sprint training (effect size = 0.29, p <0.05) groups displayed significant gains in eccentric hamstring strength. The NHE group reported trivial improvements in sprint performance, whilst the sprint training group experienced a moderate improvement, specifically in maximum speed (ES = 0.83 Moderate). Sprint training also produced greater perceptions of soreness than the NHE following a fourweek training intervention, specifically before the start of the last session (p < 0.05). CONCLUSIONSː These findings indicate that sprint training had a beneficial effect for both eccentric hamstring strength and sprint performance, whilst also producing greater soreness than the NHE following the final training session. It was concluded that a fourweek block of maximum speed training may have both an injury prevention and performance enhancement benefit.

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Freeman, BW, Talpey, SW, James, LP, Opar, DA, and Young, WB. Common high-speed running thresholds likely do not correspond to high-speed running in field sports. J Strength Cond Res 37(7): 1411–1418, 2023—The purpose of this study was to clarify what percentage of maximum speed is associated with various running gaits. Fifteen amateur field sport athletes (age = 23 ± 3.6 years) participated in a series of 55-meter running trials. The speed of each trial was determined by instructions relating to 5 previously identified gait patterns (jog, run, stride, near maximum sprint, and sprint). Each trial was filmed in slow motion (240 fps), whereas running speed was obtained using Global Positioning Systems. Contact time, stride angle, and midstance free-leg knee angle were determined from video footage. Running gaits corresponded with the following running speeds, jogging = 4.51 m·s−1, 56%Vmax, running = 5.41 m·s−1, 66%Vmax, striding = 6.37 m·s−1, 78%Vmax, near maximum sprinting = 7.08 m·s−1, 87%Vmax, and sprinting = 8.15 m·s−1, 100%Vmax. Significant (p < 0.05) increases in stride angle were observed as running speed increased. Significant (p < 0.05) decreases were observed in contact time and midstance free-leg knee angle as running speed increased. These findings suggest currently used thresholds for high-speed running (HSR) and sprinting most likely correspond with jogging and striding, which likely underestimates the true HSR demands. Therefore, a higher relative speed could be used to describe HSR and sprinting more accurately in field sports.

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