Oxygen uptake, muscle activity and ground reaction force during water aerobic exercises.

This study aimed to compare the oxygen uptake (VO2), the muscle activity of lower limbs, and the vertical ground reaction force (V-GRF) of women performing water aerobic exercises at different intensities. 12 young women performed the experimental protocol, which consisted of 3 water exercises (stationary running [SR], frontal kick [FK] and cross country skiing [CCS]) at 3 intensities (first and second ventilatory thresholds and maximum effort). A two-way repeated measures ANOVA was used. Regarding VO2, different responses between intensities (p<0.001) were found, and values between exercises were similar. For electromyographic activity (EMG), differences between intensities for all muscles (p<0.001) were found. Greater EMG signals were observed in the FK compared to SR for rectus femoris, semitendinosus, vastus lateralis and biceps femoris muscles (p<0.05). Regarding V-GRF, there was an increase in the V-GRF at greater intensities compared to the first ventilatory threshold (p=0.001). In addition, lower values were found during CCS compared to the SR and FK exercises (p<0.001). Thus, greater cardiorespiratory and neuromuscular responses were observed with increasing intensity. Exercises such as CCS could be used to attenuate the V-GRF; if the purpose is to reduce the muscular activity of lower limbs at a specific intensity, SR could be recommended.

Correlations between serum hormones, strength and endurance in healthy elderly South-American men.

AIM: Declines in muscular strength resulting from reduced serum anabolic hormones and neural activity may influence the reduction in aerobic capacity in older men. However, there has been little investigation into the relationship between steroid hormones and muscular strength, as well as endurance capacity in elderly subjects. The purpose of this study was to investigate the possible relationship between serum steroid hormones, strength and aerobic performance in older men. METHODS: Twenty-eight aged men (65±4 years) were evaluated in dynamic strength (one repetition maximum test), isometric strength (maximal voluntary contraction) and rate of force development. Peak oxygen uptake and maximal workload were determined during a ramp protocol on a cycle ergometer. In addition, blood samples were taken to determine basal cortisol, total and free testosterone. RESULTS: No correlations were found between steroid hormonal concentrations and the performance parameters investigated. CONCLUSION: Our results suggest that single measurements of steroids hormones concentrations are not related to the strength and endurance capacity of healthy South-American elderly men.

Vertical ground reaction force during water exercises performed at different intensities.

The aim of the present study was to compare the peak vertical ground reaction force (V-GRF(peak)) and impulse of women performing water aerobic exercises at different intensities in aquatic and dry land environments. 15 young women performed 1 session in each environment consisting of 3 water aerobic exercises (stationary running, frontal kick and cross country skiing) performed at 3 cadences (first ventilatory threshold, second ventilatory threshold and maximum effort, as determined during exercise in water) in a randomized order. 2-way and 3-way repeated measures ANOVA were used to analyze the impulse and V-GRF(peak), respectively. Significantly lower values of V-GRF(peak) and impulse (p<0.001) were observed for the aquatic environment. Significant differences were observed among all cadences for V-GRF(peak) and impulse (p<0.001) in both environments except for the V-GRF(peak) between the cadences corresponding to the second ventilatory threshold and maximum effort in the aquatic environment. In addition, significantly lower V-GRF(peak) values in the aquatic environment were found for cross country skiing compared to the other exercises (p<0.001). Thus, water exercises are safe for people that need to minimize vertical ground reaction force; however, an important issue to be considered during water aerobics training is the exercise and intensity to be prescribed.

3 Different types of strength training in older women.

The objective of the present study was to evaluate and compare the neuromuscular, morphological and functional adaptations of older women subjected to 3 different types of strength training. 58, healthy women (67 ± 5 year) were randomized to experimental (EG, n=41) and control groups (CG, n=17) during the first 6 weeks when the EG group performed traditional resistance exercise for the lower extremity. Afterwards, EG was divided into three specific strength training groups; a traditional group (TG, n=14), a power group (PG, n=13) that performed the concentric phase of contraction at high speed and a rapid strength group (RG, n=14) that performed a lateral box jump exercise emphasizing the stretch-shortening-cycle (SSC). Subjects trained 2 days per week through the entire 12 weeks. Following 6 weeks of generalized strength training, significant improvements occurred in EG for knee extension one-repetition (1RM) maximum strength (+19%), knee extensor muscle thickness (MT, +15%), maximal muscle activation (+44% average) and onset latency ( -31% average) for vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) compared to CG (p<0.05). Following 6 more weeks of specific strength training, the 1RM increased significantly and similarly between groups (average of +21%), as did muscle thickness of the VL (+25%), and activation of VL (+44%) and VM (+26%). The onset latency of RF (TG=285 ± 109 ms, PG=252 ± 76 ms, RG=203 ± 43 ms), reaction time (TG=366 ± 99 ms, PG=274 ± 76 ms, RG=201 ± 41 ms), 30-s chair stand (TG=18 ± 3, PG=18 ± 1, RG=21 ± 2) and counter movement jump (TG=8 ± 2 cm, PG=10 ± 3 cm, RG=13 ± 2 cm) was significantly improved only in RG (p<0.05). At the end of training, the rate of force development (RFD) over 150 ms (TG=2.3 ± 9.8 N·s(-1), PG=3.3 ± 3.2 N·s(-1), RG=3.8 ± 6.8 N·s(-1), CG=2.3 ± 7.0 N·s(-1)) was significantly greater in RG and PG than in TG and CG (p<0.05). In conclusion, rapid strength training is more effective for the development of rapid force production of muscle than other specific types of strength training and by consequence, better develops the functional capabilities of older women.

Cardiorespiratory and neuromuscular responses during water aerobics exercise performed with and without equipment.

The aim of the study was to compare the cardiorespiratory and neuromuscular responses to water aerobics exercise performed with and without equipment. 15 women performed stationary jogging combined with elbow flexion/extension without equipment, with water-drag forces equipment and with water-floating equipment, at 2 submaximal cadences and at maximal cadence. Heart rate, oxygen uptake and electromyographic signal from biceps brachii, triceps brachii, biceps femoris and rectus femoris were collected during the exercise. The heart rate and oxygen uptake showed significantly higher values during the execution of the water aerobics exercise with either equipment compared to the execution without equipment. In addition, significant difference was found between submaximal cadences. For neuromuscular responses, no significant differences were found between the submaximal cadences for all muscles analyzed; however, significant differences were found between these submaximal cadences and the maximal cadence. Similarly, the results showed no significant differences between the execution of the exercise with or without equipment, except in the muscle activation of triceps brachii and biceps femoris, which was higher when using water-floating and water-drag forces equipment, respectively. In conclusion, the water aerobics exercise presented higher cardiorespiratory responses with equipment and also increased the cadence of execution. Nevertheless, neuromuscular responses were higher only at maximal cadence.

Physiological effects of concurrent training in elderly men.

The aim of the present study was to investigate the effects of concurrent strength and endurance training on neuromuscular and hormonal parameters in elderly men. 23 healthy men (65±4 years) were randomly assigned to 1 of 3 groups: concurrent (CG, n=8), strength (SG, n=8) or endurance group (EG, n=7). The programs consisted, of strength training, endurance training on a cycle ergometer or a combination of both in the same session 3 times per week over a duration of 12 weeks. Subjects were evaluated on parameters related to muscle strength, muscle activation and serum hormones. There were significant increases in lower-body strength in all groups (P<0.05), with higher increases in SG (67%) than CG (41%) and both were higher than EG (25%) (p<0.01). Only SG and CG increased upper-body strength (p<0.01), with no significant difference between the 2 groups. Furthermore, there were significant decreases in free testosterone in EG after training. Significant increases in isometric strength and maximal muscle activation (p<0.05) as well as decreases in the submaximal muscle activation to the same load, were only seen in SG (p<0.05). The present results suggest that the interference effect observed due to concurrent strength and endurance training could be related to impairment of neural adaptations.

Cardiorespiratory responses to stationary running at different cadences in water and on land.

AIM: The aim of the current study was to analyze the heart rate (HR), oxygen uptake (V.O(2)), and percentage of maximal HR (%HR(max)) and V.O(2) (%V.O(2max)) responses to stationary running exercise performed at different cadences on land (LA) and in water (WA). METHODS: The sample comprised 12 apparently healthy women (mean age 22.33+/-0.57 years). The exercise was performed in WA and LA environments (interval of 2 hours) at submaximal cadences of 60, 80 and 100 bpm for a period of 4 min at each cadence (interval of 5 min). HR and V.O(2) data were collected using a Polar S610TM and Aerosport KB1-C gas analyzer, respectively. The data were analyzed using factorial ANOVA for mixed models, Tukey's post hoc and Pearson's correlation test, with P<0.05 (SPSS version 13.0). RESULTS: Significant differences were found between the environments for all variables (HR, V.O(2), %HR(max) and %V.O(2max): P<0.001), with higher values for LA. Significant differences were found between the cadences for all variables (HR, V.O(2), %HR(max) and %V.O(2max): P<0.001). The effect of the interaction environment cadence was only significant for %HR(max) (P=0.041). The correlations between HR and V.O(2) (WA: r=0.857; P<0.001 and LA: r=0.556; P<0.001) and %HR(max) and %V.O(2) (WA: r=0.860; P<0.001 and LA: r=0.798; P<0.001) exhibited high and significant correlation coefficient values, especially for WA, suggesting that variable increased linearly with increases in cadence. CONCLUSIONS: The results suggest that cardiorespiratory responses to stationary running exercise are lower in WA, though they can be maximized by increasing the execution cadence.