Force-velocity Profiling Of A 60 M Sprint Following 6 Weeks Of Eccentric Strength Training

The hamstrings are critical to horizontal force production during maximal sprints. Eccentric (ECC) training of the hamstring increases muscle strength, which can contribute to improvement in sprint performance. Different elements of the sprint, such as maximum velocity (vmax), horizontal force production (Fh), and power output may be altered by ECC strength. PURPOSE: To determine changes in vmax, Fh, and maximal power output (Pmax) in a 60 m sprint after a 6-week intervention performing either the Nordic Hamstring Exercise (NHE) or Romanian deadlift (RDL). METHODS: Participants were randomly allocated to the RDL or NHE training groups. Sprint testing was performed prior to training group allocation (PRE) and after 6 weeks of eccentrically-biased RDL or NHE exercises (POST). Each participant performed 3 maximal 60 m sprints with the fastest trial used for analysis. The vmax was calculated by fitting split velocities to an exponential function. Fh was calculated as body mass multiplied by the horizonal acceleration determined from the exponential function fit derivative. Pmax was calculated as Fh*vmax/4. Separate full factorial linear mixed effects models were used to assess differences between groups and across time. Summary data are presented as mean (standard deviation) and model results are presented at estimate [95% confidence interval]. RESULTS: RDL group (n = 12, age: 20.6 (0.9) years, height: 1.75 (0.1) m, mass = 72.7 (6.5) kg, males = 7) and NHE group (n = 9, age: 20.9 (1.1) years, height: 1.70 (0.1) m, mass = 68.5 (10.9) kg, males = 4) had 60 m sprint times of 8.59 (0.77) s and 8.91 (0.85) s at PRE, respectively. The POST sprint times were 8.52 (0.86) s and 8.87 (0.79) s, respectively. There were no significant group by time interactions across all sprint outcomes (vmax, p = 0.40; Fh, p = 0.81; Pmax, p = 0.79). There were no significant differences by group for vmax (p = 0.31), Fh (p = 0.25), and Pmax (p = 0.17) or by time for vmax (p = 0.62), Fh (p = 0.57), and Pmax (p = 0.21). CONCLUSIONS: ECC strength training did not improve sprint times nor did any force-velocity property change. These findings could be explained by the short training duration (6 weeks), lack of sprint-specific training, and limiting the analysis to the entire 60 m sprint. Future work will investigate the influence of each training group on acceleration split times.