Muscle Activation in World-Champion, World-Class, and National Breaststroke Swimmers.

PURPOSE: To investigate the muscle-activation patterns and coactivation with the support of kinematics in some of the world's best breaststrokers and identify performance discriminants related to national elites at maximal effort. METHODS: Surface electromyography was collected in 8 muscles from 4 world-class (including 2 world champions) and 4 national elite breaststroke swimmers during a 25-m breaststroke at maximal effort. RESULTS: World-class spent less time during the leg recovery (P = .043), began this phase with a smaller knee angle (154.6° vs 161.8°), and had a higher median velocity of 0.18 m/s during the leg glide than national elites. Compared with national elites, world-class swimmers showed a difference in the muscle-activation patterns for all 8 muscles. In the leg-propulsion phase, there was less triceps brachii activation (1 swimmer 6% vs median 23.0% [8.8]). In the leg-glide phase, there was activation in rectus femoris and gastrocnemius during the beginning of this phase (all world-class vs only 1 national elite) and a longer activation in pectoralis major (world champions 71% [0.5] vs 50.0 [4.3]) (propulsive phase of the arms). In the leg-recovery phase, there was more activation in biceps femoris (50.0% [15.0] vs 20.0% [14.0]) and a later and quicker activation in tibialis anterior (40.0% [7.8] vs 52.0% [6.0]). In the stroke cycle, there was no coactivation in tibialis anterior and gastrocnemius for world champions. CONCLUSION: These components are important performance discriminants. They can be used to improve muscle-activation patterns and kinematics through the different breaststroke phases. Furthermore, they can be used as focus points for teaching breaststroke to beginners.

Muscle coordination, activation and kinematics of world-class and elite breaststroke swimmers during submaximal and maximal efforts.

The aims of this study were to describe muscular activation patterns and kinematic variables during the complete stroke cycle (SC) and the different phases of breaststroke swimming at submaximal and maximal efforts. Surface electromyography (sEMG) was collected from eight muscles in nine elite swimmers; five females (age 20.3 ± 5.4 years; Fédération Internationale de Natation [FINA] points 815 ± 160) and four males (27.7 ± 7.1 years; FINA points 879 ± 151). Underwater cameras were used for 3D kinematic analysis with automatic motion tracking. The participants swam 25 m of breaststroke at 60%, 80% and 100% effort and each SC was divided into three phases: knee extension, knee extended and knee flexion. With increasing effort, the swimmers decreased their SC distance and increased their velocity and stroke rate. A decrease during the different phases was found for duration during knee extended and knee flexion, distance during knee extended and knee angle at the beginning of knee extension with increasing effort. Velocity increased for all phases. The mean activation pattern remained similar across the different effort levels, but the muscles showed longer activation periods relative to the SC and increased integrated sEMG (except trapezius) with increasing effort. The muscle activation patterns, muscular participation and kinematics assessed in this study with elite breaststroke swimmers contribute to a better understanding of the stroke and what occurs at different effort levels. This could be used as a reference for optimising breaststroke training to improve performance.

Effect of single bout versus repeated bouts of stretching on muscle recovery following eccentric exercise.

OBJECTIVES: To analyze the effects of a single bout and repeated bouts of stretching on indirect markers of exercise-induced muscle damage. DESIGN: A randomized controlled clinical trial at a university human research laboratory was conducted. METHODS: Fifty-six untrained males were randomly divided into four groups. (I) a single stretching group underwent a single bout of stretching on the quadriceps muscle; (II) an eccentric exercised group underwent eccentric quadriceps muscle contractions until exhaustion; (III) an eccentric exercise group followed by a single bout of stretching; (IV) an eccentric exercised group submitted to repeated bouts of stretching performed immediately and 24, 48, and 72 h post-exercise. Muscle stiffness, muscle soreness, maximal concentric peak torque, and plasma creatine kinase activity were assessed before exercise and 1, 24, 48, 72, and 96 h post-exercise. RESULTS: All exercised groups showed significant reduction in maximal concentric peak torque and significant increases in muscle soreness, muscle stiffness, and plasma creatine kinase. There were no differences between these groups in all assessed variables, with the exception of markers of muscle stiffness, which were significantly lower in the eccentric exercise group followed by single or repeated bouts. The single stretching group showed no change in any assessed variables during the measurement period. CONCLUSIONS: Muscle stretching performed after exercise, either as single bout or as repeated bouts, does not influence the levels of the main markers of exercise-induced muscle damage; however, repeated bouts of stretching performed during the days following exercise may have favorable effects on muscle stiffness.

Evidence of the physiotherapeutic interventions used currently after exercise-induced muscle damage: systematic review and meta-analysis.

INTRODUCTION: Exhaustive and/or unaccustomed exercise, mainly involving eccentric muscle actions, induces temporary muscle damage, evidenced by delayed onset muscle soreness (DOMS) and decreased muscle function. Different strategies to recover from its signs and symptoms have been studied and, as a result, a significant number of articles on this issue have been published. OBJECTIVE: To assess whether some modalities currently used in physiotherapy such as massage, cryotherapy, stretching and low-intensity exercise are effective for treating the signs and symptoms of exercise-induced muscle damage. METHODS: Randomized controlled trials (RCTs), written in English or Portuguese, that included physiotherapeutic interventions [i.e., massage, cryotherapy, stretching and low-intensity exercise, on adult human subjects (18-60 years old) of both gender] were searched on electronic databases including MEDLINE, CINHAL, EMBASE, PEDro and SPORTDiscus. MAIN OUTCOME MEASURES: "Muscle soreness" and "muscle strength" were the outcome measures included in the meta-analysis. RESULTS: Thirty-five studies were included; nine analysed the effects of massage, 10 examined the effects of cryotherapy, nine investigated the effects of stretching and seven focused on low-intensity exercise intervention. Massage was the only intervention with positive effects, reducing soreness at 24 h, on average, 0.33 on 10 cm visual analog scale (95 percent CI: -0.59, -0.07) and increasing muscle recovery by 1.87 percent (95 percent CI: 0.30, 3.44). Additionally, there is inconclusive evidence to support the use of cryotherapy, while there is little evidence to prove the efficacy of stretching and low-intensity exercise. CONCLUSION: Massage proved slightly effective in the relief of symptoms and signs of exercise-induced muscle damage. Therefore, its mean effect was too small to be of clinical relevance. There is a lack of evidence to support the use of cryotherapy, stretching and low-intensity exercise.

Gender differences in the kinematics and ball velocity of overarm throwing in elite team handball players.

The aim of this study was to investigate the throwing velocity and kinematics of overarm throwing in team handball of elite female and male handball players. Kinematics and ball velocity of a 7 metre-throw in eleven elite male (age 23.6 ± 5.2 yr, body mass 87.0 ± 6.8 kg, height 1.85 ± 0.05 m) and eleven elite female (age 20.3 ± 1.8 yr, body mass 69.9 ± 5.5 kg, height 1.75 ± 0.05 m) team handball players were recorded. The analysis consisted of maximal joint angles, angles at ball release, maximal angular velocities of the joint movements, and maximal linear velocities of the distal endpoints of segments and their timing during the throw. The ball release velocity of the male handball players was significantly higher than the females (21.1 vs. 19.2 m · s(-1); p < 0.05). No major differences in kinematics were found, except for the maximal endpoint velocities of the hand and wrist segment, indicating that male and female handball players throw with the same technique. It was concluded that differences in throwing velocity in elite male and female handball players are generally not the result of changes in kinematics in the joint movements.

EMG activation of abdominal muscles in the crunch exercise performed with different external loads.

OBJECTIVE: The aim of this study was to describe by means of surface electromyography the activation of the rectus abdominis, obliquus externus and rectus femoris muscles during the "crunch" abdominal exercise performed with loads. METHODS: Thirteen subjects performed crunch exercises with loads representing 80, 60, 40 and 20% of the 1-RM (100%) in a random order with the subjects drawing lots, and with a 5 min rest between sets. Surface bipolar EMG electrodes were used. The root mean square of the EMG was calculated for the first repetition of each load. Differences between conditions were tested using a one way ANOVA for repeated measures. Post-hoc Bonferroni tests was used to detect significant differences between specific loads (p<0.05). RESULTS: An average of the percentage values of all studied abdominal muscles was used as a representative value of abdominal synergy (Ab Syn). In general it can be concluded that the abdominal muscles were significantly more recruited in the 100% load condition. Abdominal activation significantly differed between the various loads; however, in general adjacent loads (20 vs. 40% - 1-RM) did not differ. CONCLUSIONS: These results suggest that for young, healthy and physically active adults when the objective is progression in the training process of abdominal force, the option ought to be for changes of load superior to 20% of the 1-RM.