Author(s): CORATELLA, G., LONGO, S., DORLANDO, A., STERI, E., LA SPINA, O., MOCCHI, C., CÈ, E., ESPOSITO, F., Institution: UNIVERSITY OF MILANO, Country: ITALY, Abstract-ID: 829

INTRODUCTION:
Nordic hamstrings exercise provides lengthening stimuli to the hamstrings with the intent to increase their resistive capacity to overstretching. While many longitudinal studies have found the effectiveness of NHE in increasing hamstrings strength and in elongating fascicles, the incorporation of NHE in the practice requires a deeper examination given the short-term effects due to the eccentric stimuli. Therefore, the present study investigated the exercises-induced muscle damage and the repeated-bout effect following a typical dose of NHE.
METHODS:
Thirteen active men (mean±SD; age=25.2±2.9 years; body mass=77.5±11.3 kg; height=176.4±8.4 cm) were recruited. Hamstrings eccentric strength, muscle soreness, passive range of motion (ROM), anatomical cross-sectional area and echo-intensity of biceps femoris, semitendinosus and semimembranosus were assessed at baseline, and up to four days after the NHE bout. The repeated-bout effect was examined after four weeks by repeating the same procedures. NHE session consisted of 4 x 6 repetitions. A two-way repeated-measures ANOVA as statistical analysis.
RESULTS:
After the first bout, hamstrings eccentric strength decreased and remained below the baseline up to three days (average loss: -25%, mean Cohen’s d effect size [ES] ranging from -3.88 to -2.95, p<0.05); muscle soreness increased two days after and remained higher up to four days (mean ES ranging from 1.30 to 1.62, p<0.05); passive ROM decreased up to four days (mean ES ranging from 0.64 to 1.62, p<0.05); anatomical cross-sectional area and echo intensity did not show any changes, both for the separate and combined muscles (p>0.05 for all comparisons). After the second bout, hamstrings eccentric strength decreased and remained below baseline up to one day (-22.5%, ES: -1.79, p<0.05); muscle soreness did not increase; passive ROM decreased up to two days (mean ES -ranging from -0.85 to -0.77); no change occurred in cross-sectional area and echo intensity.
CONCLUSION:
A typical dose of NHE showed impairments in muscle function but did not affect muscle structure. The current data offer novel perspectives on incorporating NHE into the weekly routine, since defining the recovery time course after a typical NHE dose. Additionally, the recovery after the second bout is much faster. In the practice, a first bout of NHE is suggested to be included far from competitions or a congested training routine, while a second bout can be safely incorporated without any meaningful impairments in the following days.