Symmetry in the front crawl stroke of different skill level of able-bodied and disabled swimmers

Copyright: © 2020 Santos et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Although swimming is recognized as a symmetrical sport, equivalence between each body side cannot be insured. Swimmers with physical and motor impairment may present asymmetries that are even more pronounced. Therefore, the objective of this study was to assess the symmetry of temporal coordination in the front crawl stroke phases and their dimensional characteristics among swimmers of different levels of skill and disabled swimmers. Forty-one swimmers (28 men and 13 women, 18,8 ± 3,3 years, divided 21 of them into groups of high and low level of skill and 20 in disabled swimmers group) performed a 50m maximum of front-crawl test while they were recorded by six synchronized cameras (four underwater and two above water) for analysis of the stroke phases, stroke dimensions (anteroposterior, mediolateral and vertical amplitude), index of coordination and hand speed. The symmetry index was calculated by the difference between the right and the left strokes. Comparisons were made using the Kruskal-Wallis test and multivariate comparisons were made using the Mann-Whitney test, with p <0.05. Asymmetry was noted in anteroposterior and mediolateral amplitudes of the stroke, index of coordination, duration of the recovery phase, each of the underwater phases and in the hand speed during the downseep phase, regardless of the level of skill or impairment. The disabled swimmers also showed asymmetry in the vertical amplitude of the stroke as well as in the insweep and upsweep speed. The reasons for these asymmetries may be the preference for unilateral breathing, force imbalance between pairs of homologous muscles and motor control deficit. The training with stereotypic movements may explain the similarity of asymmetries among the different groups of swimmers

Front crawl swimming performance and bi-lateral force asymmetry during land-based and tethered swimming tests

©Journal of Sports Science and Medicine. The aims of this study were to investigate whether land-based and tethered swimming strength tests can explain swimming performance in 200-meter front crawl and, whether these tests were able to identify bilateral symmetry in force production. In the first session, eighteen swimmers completed a maximum effort 200 m front crawl swim (swimming performance) and 15 seconds maximal effort tethered front crawl swim. In the second session, participants performed the upper extremity isometric strength test. Peak force production of tethered swimming and isometric strength tests were significantly correlated for the strongest and weakest sides (r = 0.58 and r = 0.63, respectively; p < 0.05), but only peak force production during tethered swimming correlated with 200 m swimming performance time (r = -0.55, p < 0.05). Bilateral asymmetries in peak force and rate of force development were similar between the tethered swimming and isometric strength tests (peak force: 13%, p = 0.24; rate of force development: 15%, p = 0.88) However, both tests detected significant difference of peak force and rate of force development between body sides. The tethered swimming test can partially explain the 200 m front crawl swimming performance. In addition, the land-based and tethered swimming tests may be used to identify bilateral asymmetry of swimming

Age-related changes in the rate of muscle activation and rapid force characteristics

Declines in muscle size and strength are commonly reported as a consequence of aging; however, few studies have investigated the influence of aging on the rate of muscle activation and rapid force characteristics across the lifespan. This study aims to investigate the effects of aging on the rate of muscle activation and rapid force characteristics of the plantar flexors. Plantar flexion peak force (PF), absolute (peak, 50, and 100–200 ms), and relative (10 %, 30 %, and 50 %) rate of force development (RFD), the rapid to maximal force ratio (RFD/PF), and the rate of electromyography rise (RER) were examined during an isometric maximal voluntary contraction (MVC) in young (age = 22 ± 2 years), middle-aged (43 ± 2 years), and old (69 ± 5 years) men. The old men exhibited lower PF (30.7 % and 27.6 % lower, respectively) and absolute (24.4–55.1 %) and relative (16.4–28.9 %) RFD values compared to the young and middle-aged men (P ≤ 0.03). RER values were similar between the young and old men (P ≥ 0.30); however, RER values were greater for the middle-aged men when compared to the young and old men for the soleus (P < 0.01) and the old men for the medial gastrocnemius (P ≤ 0.02). Likewise, RFD/PF ratios were similar between young and old men (P ≥ 0.26); however, these ratios were greater for the middle-aged men at early (P ≤ 0.03), but not later (P ≥ 0.10), time intervals. The lower PF and absolute and relative RFD values for the old men may contribute to the increased functional limitations often observed in older adults. Interestingly, higher rates of muscle activation and greater early RFD/PF ratios in middle-aged men may be a reflection of physiological alterations in the neuromuscular system occurring in the fifth decade