No abstract

Zemková, E, Cepková, A, Uvaček, M, and Šooš, L. A novel method for assessing muscle power during the standing cable wood chop exercise. J Strength Cond Res 31(8): 2246-2254, 2017-The study estimates the repeatability and sensitivity of a novel method for assessing (a) the maximal power during the standing cable wood chop exercise with different weights and (b) the endurance of the core muscles. A group of 23 fit men performed (a) maximal effort single repetitions of the standing cable wood chop exercise with weights increasing stepwise up to 1 repetition maximum (1RM) and (b) a set of 20 repetitions at a previously established weight at which maximal power was achieved. Results showed that mean power during the standing cable wood chop exercise is a reliable parameter, with intraclass correlation coefficient values above 0.90 for all weights tested. It was also shown to be a sensitive parameter able to discriminate within-group differences in the maximal power and endurance of core muscles. Substantial individual differences were found in mean power, especially at higher weights, and in the maximal power achieved at about 75% of 1RM (462.2 ± 57.4 W, n = 11), 67% of 1RM (327.2 ± 49.7 W, n = 7), and 83% of 1RM (524.0 ± 63.2 W, n = 5). At these weights, there were also significant differences between the initial and the final repetitions of the wood chop exercise (13.9%, p = 0.025; 10.2%, p = 0.036; and 13.8%, p = 0.028, respectively). These findings indicate that evaluation of the maximal power and endurance of the core muscles during the standing cable wood chop exercise on a weight stack machine is a reliable method and sensitive to differences among physically active individuals.

This study evaluates the effect of 8 weeks of the stable and unstable resistance training on muscle power. Thirty-three healthy men recreationally trained in resistance exercises, randomly assigned into two groups, performed resistance exercises either under stable or unstable conditions for 8 weeks (three sessions per week). Before and after 4 and 8 weeks of the training, they underwent squats and chest presses on either a stable surface or on a BOSU ball and a Swiss ball respectively with increasing weights up to at least 85% 1RM. Results showed significant improvements of mean power during chest presses on a Swiss ball at weights up to 60.7% 1RM after 4 and 8 weeks of the instability resistance training. Mean power increased significantly also during squats on a BOSU ball at weights up to 48.1% 1RM after 4 but not 8 weeks of instability resistance training. However, there were no significant changes in mean power during bench presses and squats on a stable support surface after the same training. These findings indicate that there is no cross effect of instability resistance training on power produced under stable conditions. This confirms and complies with the principle for specificity of training.

This study compares the differences in peak and mean power in the acceleration, as well as over the entire concentric phase of jumps and squats performed with and without countermovement (i.e. delta power) in athletes of different specializations. The participants performed either barbell squats or barbell jumps with and without countermovement bearing a weight of 70% 1RM. Results identified a significantly higher delta mean power in the entire concentric phase of jumps than in squats for high jumpers (29.8%, p=0.009) and volleyball players (24.3%, p=0.027). More specifically, their values were significantly higher during jumps in indoor volleyball players but not in beach volleyball players. On the other hand, rock & roll performers exhibited a significantly higher delta mean power during squats than jumps (19.5%, p=0.034) but this was only evident in those who specialized in acrobatics as opposed to dance. However, the values did not differ significantly during either jumps or squats for hockey players (9.5%, p=0.424) and karate competitors (11.6%, p=0.331). A similar trend was observed for peak and mean power in the acceleration phase of jumps and squats. It may be concluded then, that enhancement of power in the concentric phase of jumps and squats bearing an external load, differs in athletes with diverse demands on the explosive strength of their lower limbs. For most athletes, jumping may be considered a more specific alternative for the estimation of the

Background: seated behaviour and a lack of physical activity among university students may cause changes to posture leading to health problems. We were interested whether between-gender differences in spinal curvature exist among university students with a predominantly sedentary lifestyle. Methods: a group of 20 female (age 20 ± 0.73 years) and 39 male (age 20 ± 1.08 years) university students with a predominantly sedentary lifestyle participated in the study. The thoracic and lumbar curvature was evaluated while standing and sitting using the Spinal Mouse. Results: showed that 10% of the female students and 30.77% of the male students had thoracic hyperkyphosis, while 10% of the female students and 2.56% of the male students suffered from lumbar hyperlordosis in the standing posture. In the sitting posture, 0% of the females and up to 30.77% of the males had mild thoracic hyperkyphosis, and 25.00% of the females and 23.90% of the males had mild lumbar hyperkyphosis. Conclusions: these findings indicate that differences between the sexes as regards to curvature of the spine exist. Prolonged sitting during university courses could contribute to their poor posture. It is therefore necessary to focus purposefully on compensation exercises that eliminate postural deviations in female and male young adults.