Biomechanical Response to Acute Stretching in Dancers and Non-Dancers.

This study aimed to investigate the bio- mechanical response of the hamstring muscles to acute stretching in dancers (D) compared to non-dancers (ND). Maximal range of motion (ROMMax) and stiffness of the hamstrings were assessed in 46 young males, 23 undergraduate students (ND) and 23 professional dancers (D). Ages of the two groups were D 21.5 ± 0.60 years; ND 27.5 ± 0.98 years). Testing was performed in two sessions, familiarization with procedures in the first session and the tests themselves (pre- and post-test and intervention) in the second, with a 24- to 48-hour interval between. The pre-test consisted of three trials of passive knee extension to the point of increased tension in the hamstrings, defined as ROMMax. The resistance torque recorded at ROMMax was defined as torqueMax. Six 30-second constant torque stretches were performed at 100% of the torqueMaxreached in the pre-test in one lower limb only (intervention), with the contralateral limb used as control. The torque measured at an identical ROM before (pre-test) and after (post-test) the intervention was defined as torqueROM, and represented stiffness in this study. Reliability of the ROMMax, torqueMax, and torqueROMwas assessed via intraclass correlation coefficients (ICC3, k) and standard error of the measurements (SEM). Comparison between dancers and non-dancers, control, and intervention conditions for all dependent variables was performed using ANOVA repeated measures followed by Tukey post hoc comparisons to highlight any interaction. The submaximal stretch intensity applied caused torqueROM to decrease in both D and ND groups (p < 0.01), indicating a decrease in stiffness, but no difference between the groups was found. A significantly greater increase in ROMMax was found for the D group compared to the ND group (p < 0.01), suggesting that other aspects in addition to MTU biomechanical adaptations may have played a role in the ROMMax increase, especially for the D group. Further research is needed to explore what those other adaptations are. Meanwhile, coaches and physical therapists should be aware that dancers may require different stretch training protocols than non-dancers.

Variations in Repetition Duration and Repetition Numbers Influence Muscular Activation and Blood Lactate Response in Protocols Equalized by Time Under Tension.

The aim of this study was to investigate the impact of protocols equalized by the time under tension (TUT) but composed of different repetition durations and repetitions numbers on muscle activation and blood lactate concentration. Twenty-two males with previous experience in resistance training performed 2 training protocols (A and B) with the Smith machine bench press exercise, both with 3 sets, 3 minutes' rest, and 60% of 1 repetition maximum (1RM). Protocol A consisted of 6 repetitions with a 6-second repetition duration for each repetition, whereas in Protocol B the subjects performed 12 repetitions with a 3-second repetition duration for each repetition. Muscular activation was measured in the anterior deltoid, pectoralis major, and triceps brachii muscles while performing the 2 protocols, and the normalized root mean square of the electromyographic signal (EMGRMS) was calculated for each set. Blood lactate concentrations were measured during and until 12 minutes after the completion of each protocol. The results showed that the EMGRMS of all muscles increased during the sets and was higher in Protocol B when compared with Protocol A. Likewise, blood lactate concentrations also increased throughout the sets and were higher in Protocol B both during and after the completion of each training session. The data obtained in this study show that training protocols conducted with the same TUT, but with different configurations, produce distinct neuromuscular and metabolic responses so that performing higher repetition numbers with shorter repetition durations might be a more appropriate strategy to increase muscle activation and blood lactate concentration.