The effects of replacing a portion of endurance training by explosive strength training on performance in trained cyclists

To investigate the effects of replacing a portion of endurance training by strength training on exercise performance, 14 competitive cyclists were divided into an experimental (E; n=6) and a control (C; n=8) group. Both groups received a training program of 9 weeks. The total training volume for both groups was the same [E: 8.8 (1.1) h/week; C: 8.9 (1.7) h/week], but 37% of training for E consisted of explosive-type strength training, whilst C received endurance training only. Simulated time trial performance (TT), short-term performance (STP), maximal workload ( ) and gross (GE) and delta efficiency (DE) were measured before, after 4 weeks and at the end of the training program (9 weeks). No significant group-by-training effects for the markers of endurance performance (TT and ) were found after 9 weeks, although after 4 weeks, these markers had only increased (P<0.05) in E. STP decreased (P<0.05) in C, whereas no changes were observed in E. For DE, a significant group-by-training interaction (P<0.05) was found, and for GE the group-by-training interaction was not significant. It is concluded that replacing a portion of endurance training by explosive strength training prevents a decrease in STP without compromising gains in endurance performance of trained cyclists. Electronic Publication     

The effects of creatine supplementation on muscular performance and body composition responses to short-term resistance training overreaching

To determine the effects of creatine supplementation during short-term resistance training overreaching on performance, body composition, and resting hormone concentrations, 17 men were randomly assigned to supplement with 0.3 g/kg per day of creatine monohydrate (CrM: n=9) or placebo (P: n=8) while performing resistance exercise (5 days/week for 4 weeks) followed by a 2-week taper phase. Maximal squat and bench press and explosive power in the bench press were reduced during the initial weeks of training in P but not CrM. Explosive power in the bench press, body mass, and lean body mass (LBM) in the legs were augmented to a greater extent in CrM (P0.05) by the end of the 6-week period. A tendency for greater 1-RM squat improvement (P=0.09) was also observed in CrM. Total testosterone (TT) and the free androgen index (TT/SHBG) decreased in CrM and P, reaching a nadir at week 3, whereas sex hormone binding globulin (SHBG) responded in an opposite direction. Cortisol significantly increased after week 1 in CrM (+29%), and returned to baseline at week 2. Insulin was significantly depressed at week 1 (–24%) and drifted back toward baseline during weeks 2–4. Growth hormone and IGF-I levels were not affected. Therefore, some measures of muscular performance and body composition are enhanced to a greater extent following the rebound phase of short-term resistance training overreaching with creatine supplementation and these changes are not related to changes in circulating hormone concentrations obtained in the resting, postabsorptive state. In addition, creatine supplementation appears to be effective for maintaining muscular performance during the initial phase of high-volume resistance training overreaching that otherwise results in small performance decrements.     

Effect of intense swimming training on rhinitis in high‐level competitive swimmers

Background Rhinitis is commonly reported by swimmers. Seasonal allergic rhinitis may impair athletes' performance and quality of life (QOL). No data are currently available on the changes of nasal symptoms during and after a swimming season. We aimed to determine in competitive swimmers: (1) the prevalence of rhinitis and its impact on their QOL during an intense training programme, (2) the changes in nasal symptoms and QOL after a resting period and (3) the relationship between rhinitis and airway hyperresponsiveness (AHR). Methods Thirty‐nine swimmers and 30 healthy controls answered the Rhinitis Quality of Life Questionnaire (RQLQ) and scored nasal symptoms on a seven‐point Likert scale during the week preceding their visit. Subjects had allergy skin prick tests and a methacholine challenge. Peak nasal inspiratory flows were also measured. The athletes performed these tests during an intense training period (V1), outside the pollen season and after at least 2 weeks without swimming (V2). Results At V1, rhinitis symptoms were reported by 74% of swimmers and 40% of controls (P<0.01). Eighty‐four percent of swimmers and 72% of controls were atopic (NS). RQLQ score was higher in swimmers compared with controls at V1 (27.3 ± 28.5 vs. 9.5 ± 12.7, respectively, P<0.005). The presence of AHR during training did not correlate with the presence of rhinitis symptoms. At V2, the nasal symptoms and RQLQ scores were similar in swimmers and controls. Conclusion Intense swimming training is associated with an increase in nasal symptoms and impairment in QOL in most competitive swimmers. Such an increase is not related to seasonal allergen exposure in atopic athletes and probably results from chlorine derivative exposure. Cite this as: V. Bougault, J. Turmel and L. P. Boulet, Clinical & Experimental Allergy, 2010 (40) 1238–1246.     

Effect of intensive exercise‐induced testicular gametogenic and steroidogenic disorders in mature male Wistar strain rats: a correlative approach to oxidative stress

Aims: In order to investigate the effects of intensive exercise on reproductive dysfunctions in relation to oxidative stress, a total of 12 male rats (age: 3 months, weight: 127 ± 2.86 g) were randomly divided into: (1) control group (CG, n = 6) and (2) experimental group (Exp. G, n = 6). Methods: An exercise protocol of 3 h swimming day^?1, 5 days week^?1 was followed for 4 weeks in Exp. G, with no exercise in CG. All the animals were killed; blood, testes and the accessory sex organs were collected for estimation of different parameters. Results: A significant diminution (P < 0.001) was noted in testicular Δ⁵, 3β‐hydroxy‐steroid dehydrogenase (Δ⁵, 3β‐HSD), 17β‐hydroxy steroid dehydrogenase (17β‐HSD); plasma levels of testosterone, luteinizing hormone (LH); preleptotine spermatocytes (pLSc), midpachytene spermatocytes (mPSc) and stage 7 spermatids (7Sd); with no significant alteration in follicle stimulating hormone (FSH) and spermatogoia A (Asg) after intensive exercise. A significant elevation (P < 0.001) in malondialdehyde (MDA) and conjugated dienes (CD) along with significant reduction (P < 0.001) in glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione‐s‐transferase (GST) and peroxidase were found in testes of Exp. G. Moreover, the somatic index of testes and accessory sex organs were also decreased significantly (P < 0.001) after exercise. High correlations have been found in 17 β‐HSD with CAT (r = 0.90, P < 0.05) and peroxidase (r = 0.83, P < 0.05), epididymal somatic index with CD (r = ?0.91; P < 0.05) and GSH (r = 0.84, P < 0.05). Conclusion: The present study focused an chronic intensive exercise‐induced oxidative stress that may cause dysfunctions in male reproductive system including steroidogenesis and spermatogenesis.     

Heart rate dynamics after controlled training followed by a home-based exercise program

Daily aerobic training results in autonomic control of the heart toward vagal dominance. The constancy of vagal dominance after controlled training followed by a home-based training program in accordance with contemporary guidelines is not known. We set out here to study whether the vagal dominance induced by 8 weeks of controlled aerobic training is preserved after a 10-month home-based training program. For the controlled study, healthy men were randomized as training (n=18) and control subjects (n=6). The training was started by a supervised 8-week period with six training sessions a week [45 (15) min each] at an intensity of 70–80% of maximum heart rate, followed by a home-based training program for 10 months in accordance with the American College of Sports Medicine recommendations. Cardiovascular autonomic function was assessed by analyzing HR variability over a 24-h period and separately during the night hours (midnight–6 a.m.). Maximal running performance improved during the controlled training 16 (7)% (range 4–31%, P<0.001) and remained 8 (8)% (range –3 to 23%, P<0.001) above the baseline level after the home-based training program. At night, the vagally mediated high-frequency (HF) power of R-R intervals increased during the controlled training from 6.7 (1.3) to 7.3 (1.1) ln ms² (P<0.001) and remained higher than the baseline after the home-based training [7.0 (1.3) ln ms², P<0.05]. The changes in running performance correlated with the changes in HF power at night (r=0.41, P<0.05) and over 24 h (r=0.44, P<0.05) after the home-based training program. Similarly, the changes in body mass index correlated with the changes in HF power over 24 h (r=–0.44, P<0.05) after the home-based training program. The high vagal outflow to the heart after the home-based training is associated with good physical performance and body mass control.     

Cortisol,testosterone, and insulin action during intense swimming training in humans

An increase in the amounts of circulating plasma cortisol or a decrease in testosterone can result in whole-body insulin resistance. The purpose of this study was to determine if the increase in cortisol and/or decrease in testosterone concentrations commonly evident with intense endurance training is associated with insulin resistance. Male (n = 9) and female (n = 10) swimmers were examined during the off-season, after 9 weeks (9 WKS) of training averaging 5,500 m·day^–1 and after an additional 9 weeks (18 WKS) of training averaging 8,300 m·day^–1. Resting plasma cortisol concentration was (P <– 0.05) higher in the women compared to the men at 9 WKS; values were not significantly different between genders at 18 WKS. Plasma testosterone concentration decreased significantly (P <– 0.05) in the men at 9 and 18 WKS, but did not change in the women. Whole-body insulin action, as determined by insulin and glucose responses during a 120 min, 75-g oral glucose tolerance test, did not change with training in either the men or women. These data indicated that plasma testosterone concentration can decrease in male swimmers during intense endurance training; this alteration does not affect whole-body insulin action. There would also appear to be a gender-specific response of plasma cortisol to endurance training, which does not influence insulin action.     

Effect of concurrent strength and endurance training on skeletal muscle properties and hormone concentrations in humans

The purpose of this study was to investigate the effect of concurrent strength and endurance training on strength, endurance, endocrine status and muscle fibre properties. A total of 45 male and female subjects were randomly assigned to one of four groups; strength training only (S), endurance training only (E), concurrent strength and endurance training (SE), or a control group (C). Groups S and E trained 3 days a week and the SE group trained 6 days a week for 12 weeks. Tests were made before and after 6 and 12 weeks of training. There was a similar increase in maximal oxygen consumption (V˙O_{2 max}) in both groups E and SE (P < 0.05). Leg press and knee extension one repetition maximum (1 RM) was increased in groups S and SE (P < 0.05) but the gains in knee extension 1 RM were greater for group S compared to all other groups (P < 0.05). Types I and II muscle fibre area increased after 6 and 12 weeks of strength training and after 12 weeks of combined training in type II fibres only (P < 0.05). Groups SE and E had an increase in succinate dehydrogenase activity and group E had a decrease in adenosine triphosphatase after 12 weeks of training (P < 0.05). A significant increase in capillary per fibre ratio was noted after 12 weeks of training in group SE. No changes were observed in testosterone, human growth hormone or sex hormone binding globulin concentrations for any group but there was a greater urinary cortisol concentration in the women of group SE and decrease in the men of group E after 12 weeks of training (P < 0.05). These findings would support the contention that combined strength and endurance training can suppress some of the adaptations to strength training and augment some aspects of capillarization in skeletal muscle. Accepted: 10 November 1998     

Effects of three tapering techniques on the performance, forces and psychometric measures of competitive swimmers

The 100-m and 400-m swim time, tethered swimming forces, mood states and self-ratings of well-being of 27 competitive swimmers were measured before and after 4 weeks of intense training and after 1 week and 2 weeks of tapering for major competition. The swimmers were divided into three groups. Each group completed one of three taper regimes similar to those currently performed by swimmers in preparation for competition: (a) reduced training frequency according to each athlete's daily ratings of well-being, (b) reduced training volume, and (c) reduced training volume and intensity. Significant improvements in the Profile of Mood States measures of tension, depression and anger (P?P?P?P?>?0.05) were observed and no significant differences were revealed among the three tapering techniques. These data highlighted the importance of providing sufficient recovery before competition, since 1 week of reduced training was not long enough to maximise the benefits of tapering. However, none of the three types of tapering currently used by competitive swimmers could be shown to be more beneficial than the others.     

Serum hormones and physical performance capacity in young boy athletes during a 1-year training period

Summary Serum hormones and physical performance capacity in boy athletes (AG;n = 19) were investigated during a 1-year training period (between the ages of 11.6 and 12.6 years). Six young untrained boys served as the control group (CG). The mean serum testosterone concentration increased significantly in AG (P<0.05) following the training period from 2.92 nmol·l^–1, SD 1.04 to 5.81 nmol·l^–1, SD 1.33. Significant differences were not observed in the cortisol, sex hormone binding globulin and growth hormone levels during the follow-up period. The AG clearly increased speed (P<0.001), speed-strength (P<0.01-P<0.001) and anaerobic capacity (P<0.001) whereas CG had only slight increases (NS) in physical performance capacity during a 1-year period. During the last 6-month training period significant positive correlations (r=0.490–0.58;P<0.05 -P<0.01) were observed in AG between the relative changes in testosterone, testosterone: cortisol ratio and growth hormone and the relative performance change in speed, maximal isometric force and endurance, respectively. At the end of the period significant positive correlations were observed in all subjects between the level of testosterone and speed-strength (r=0.52–0.64;P<0.01 -P<0.001) and anaerobic capacity (r=0.49;P<0.05). It was concluded that an increase in anabolic activity with the synchronous training already has positive effects on trainability and physical performance capacity at an early stage in puberty.     

Increased oxidative stress indices in the blood of child swimmers

The blood redox status of child athletes is compared with that of age-matched untrained individuals. In the present study, 17 swimmers (10.1 ± 1.6 years) and 12 non-athletes (9.9 ± 1.1 years) participated. Reduced glutathione (GSH) was lower by 37% in swimmers compared to non-athletes (P < 0.01), oxidized glutathione (GSSG) was not different and their ratio (GSH/GSSG) was lower by 43% in swimmers compared to non-athletes (P < 0.01). Thiobarbituric acid-reactive substances concentration was higher by 25% in swimmers compared to controls. Catalase exhibited a strong trend toward lower levels in swimmers (P = 0.08). Finally, total antioxidant capacity was found lower by 28% in swimmers compared to controls (P < 0.05). In conclusion, we report that children participating in swimming training exhibit increased oxidative stress and less antioxidant capacity compared to untrained counterparts and suggest that children may be more susceptible to oxidative stress induced by chronic exercise.     

Effect of 6 weeks of sprint training on growth hormone responses to sprinting

This study examined the effect of 6 weeks of prescribed sprint training on the human growth hormone (hGH) response to cycle ergometer sprinting. Sixteen male subjects were randomly assigned to a training (n=8) or a control (n=8) group. Each subject completed two main trials, consisting of two all-out 30-s cycle-ergometer sprints separated by 60 min of passive recovery, once before, and once after a 6-week training period. The training group completed three supervised sprint-training sessions per week in addition to their normal activity, whilst control subjects continued with their normal activity. In the training group, peak and mean power increased post-training by 6% (P<0.05) and 5% (P<0.05), respectively. Post-exercise blood pH did not change following training, but the highest post-exercise blood lactate concentrations were greater [highest measured value: 13.3 (1.0) vs 15.0 (1.1) mmol l^–1], with lower blood lactate concentrations for the remainder of the recovery period (P<0.05). Post-exercise plasma ammonia concentrations were lower after training [mean highest measured value: 184.1 (9.8) vs 139.0 (11.7) mol l^–1, P<0.05]. Resting serum hGH concentrations did not change following training, but the peak values measured post-exercise decreased by over 40% in the training group [10.3 (3.1) vs 5.8 (2.5) g l^–1, P<0.05], and mean integrated serum hGH concentrations were 55% lower after training [567 (158) vs 256 (121) min g l^–1, P<0.05]. The hGH response to the second sprint was attenuated similarly before and after training. This study showed that 6 weeks of combined speed- and speed-endurance training blunted the human growth hormone response to sprint exercise, despite an improvement in sprint performance.     

Resistance exercise-induced increase in muscle mass correlates with p70S6 kinase phosphorylation in human subjects

The purpose of the present study was to investigate the possible relationship between a change in Thr³⁸⁹ phosphorylation of p70S6 kinase (p70^S6k) after a single resistance training session and an increase in skeletal muscle mass following short-term resistance training. Eight male subjects performed an initial resistance training session in leg press, six sets of 6RM with 2 min between sets. Muscle biopsies were obtained from the vastus lateralis before (T1) and 30 min after the initial training session (T2). Six of these subjects completed a 14-week resistance-training programme, three times per week (nine exercises, six sets, 6RM). A third muscle biopsy was obtained at the end of the 14-week training period (T3). One repetition maximum (1RM) squat, bench press and leg press strength as well as fat-free mass (FFM, with dual energy X-ray absorptiometry) were determined at T1 and T3. The results show that the increase in Thr³⁸⁹ phosphorylation of p70^S6k after the initial training session was closely correlated with the percentage increase in whole body FFM (r = 0.89, P < 0.01), FFM_leg (r = 0.81, P < 0.05), 1RM squat (r = 0.84, P < 0.05), and type IIA muscle fibre cross sectional area (r = 0.82, P < 0.05) after 14 weeks of resistance training. These results may suggest that p70^S6k phosphorylation is involved in the signalling events leading to an increase in protein accretion in human skeletal muscle following resistance training, at least during the initial training period.     

Strength training effects on physical performance and serum hormones in young soccer players

To determine the effects of simultaneous explosive strength and soccer training in young men, 8 experimental (S) and 11 control (C) players, aged 17.2 (0.6) years, were tested before and after an 11-week training period with respect to the load-vertical jumping curve [loads of 0–70 kg (counter-movement jump CMJ0–70)], 5- and 15-m sprint performances, submaximal running endurance and basal serum concentrations of testosterone, free testosterone and cortisol. In the S group, the 11-week training resulted in significant increases in the low-force portion of the load-vertical jumping curve (5–14% in CMJ0–30, P<0.01) and in resting serum total testosterone concentrations (7.5%, P<0.05), whereas no changes were observed in sprint running performance, blood lactate during submaximal running, resting serum cortisol and resting serum free testosterone concentrations. In the C group, no changes were observed during the experimental period. In the S group, the changes in CMJ0 correlated (P<0.05–0.01) with the changes in the 5-m (r=0.86) and 15-m (r=0.92) sprints, whereas the changes in CMJ40 correlated negatively with the changes in the testosterone:cortisol ratio (r=–0.84, –0.92, respectively, P<0.05). These data indicate that young trained soccer players with low initial strength levels can increase explosive strength by adding low-frequency, low-intensity explosive-type strength training. The inverse correlations observed between changes in CMJ40 and changes in the testosterone:cortisol ratio suggest that a transient drop in this ratio below 45% cannot always be interpreted as a sign of overstrain or neuroendocrine dysfunction.An erratum to this article can be found at     

Total blood volume in endurance-trained postmenopausal females: relation to exercise mode and maximal aerobic capacity

We have recently shown that postmenopausal female distance runners demonstrate elevated levels of blood volume compared with sedentary healthy peers. We also found a strong positive relation between blood volume and maximal oxygen consumption. In young adult males, endurance exercise training increases blood volume when performed in the upright, but not in the supine body position. Based on these observations, we hypothesized that among postmenopausal females, the elevation in blood volume would be absent or attenuated in women who train in the horizontal vs. upright body position, and that the lower blood volume in the former would be associated with lower maximal aerobic capacity. Thus, we measured supine resting plasma and total blood volumes (Evans blue dye) and maximal oxygen consumption in postmenopausal women: 10 sedentary controls, 10 swimmers and 10 runners matched for age (60 ± 2; 59 ± 2; 58 ± 2 years, mean ± SE) and hormone replacement use (5 per group). The swimmers and runners were further matched for training volume (4.5 ± 0.2 vs. 4.8 ± 0.6 h week^–1), relative performance (78 ± 5 vs. 75 ± 3% of age-group world record) and fat-free mass (45.5 ± 0.8 vs. 44.9 ± 1.5 kg). Total blood volume and maximal oxygen consumption were highest in the runners (81.2 ± 4; 52.4 ± 3 mL kg^–1, respectively) and progressively lower in the swimmers (68.8 ± 3; 44.2 ± 2) and controls (59.2 ± 2; 37.9 ± 2; all P < 0.05). In the pooled population, blood volume was positively related to maximal oxygen consumption (r= 0.72, P < 0.0001). We conclude that in endurance-trained postmenopausal females matched for training volume and competitive performance: (1) blood volume is lower in those who train in the horizontal (swimmers) compared with the upright position (runners); (2) the lower blood volume is associated with a lower maximal aerobic capacity. Nevertheless, blood volume and maximal oxygen consumption are higher in postmenopausal women who train in the horizontal position than in sedentary controls.     

Preparatory versus main competitions: differences in performances, lactate responses and pre-competition plasma cortisol concentrations in elite male swimmers

Two groups of elite male swimmers were studied using a similar protocol during the winter training seasons of two consecutive years. In the first season (September 1997–January 1998), eight male swimmers (age 19–25 years) of the Italian National Team participated, after 12 weeks of increased training volume, in a preparatory national competition (PWC) and then, after a further 6 weeks of specific training, in the World Championships (WC, both competitions in a 50-m pool), which represented the main competition at the end of the 18-week-long winter season. In the second season (September 1998–December 1998), a group of ten high-level male swimmers (18–22 years) participated, after 8 weeks of increased training volume, in a preparatory national competition (PIC) and then, after a further 6 weeks of specific training, in the Italian Championships (IC, both competitions in a 25-m pool), the main competition at the end of the 14-week-long winter season. A tapering period lasting 1–3 weeks was observed before the main competition in both seasons. All swimmers were competing at distances of up to 400 m; two of them participated in the study in both seasons. The swimming velocities and post-competition blood lactate concentrations were higher in the main competitions than in the preparatory competitions in both seasons. Pre-competition plasma cortisol (CORT) concentrations were higher than the initial values at the beginning of the season, reaching maximal values at the preparatory competitions and then decreasing before the main competitions in both seasons. The percentage increase in individual swimming velocity from the preparatory to the main competition was positively correlated with the corresponding increase in post-competition blood lactate (r=0.63, P=0.046) in the 1997 season (WC), and negatively correlated with the corresponding decrease in pre-competition CORT concentration (r=−0.66, P=0.019) in the 1998 season (IC). Our results indicate that a decrease in pre-competition CORT could be a prerequisite for an improvement in swimming performance. Accepted: 9 March 2000     

Resting thyroid and leptin hormone changes in women following intense,prolonged exercise training

This study examined whether free (f) triidothyronine (T3), f thyroxine (T4), thyroid stimulating hormone (TSH), and leptin concentrations at rest changed in response to 20 weeks of exercise-training. Two groups of women were recruited for participation in the study, collegiate athletes (n=17) and sedentary controls (n=4). Exercise training consisted of daily athletic activity such as rowing, running, and weight lifting. Subjects were initially grouped into rowers and controls. However, earlier suggested criteria were further used to categorize hormone changes (percentages) in the subjects into (+) responders (increases), (–) responders (decreases), or non-responders (no changes). The fT3 results of the rowers revealed two distinct categories of responses, (–) responder (all decreases; n=10) and non-responder (no change; n=7) rowers. In the responders fT3 concentration decreased (P<0.05) from baseline (BL) during an intense training period [(mean SEM) at 5 weeks by –28.2 (6.2)% and at 10 weeks by –24.9 (7.9)%], then returned towards BL levels (20 weeks compared to BL, P>0.05). Similar changes (P<0.05), at comparable times, were noted for letpin and TSH concentrations in the (–) responder rowers. The non-responder rowers and control subjects displayed no significant (P>0.05) hormone changes over the 20 weeks. The hormone changes observed in the (–) responder rowers were not significantly (P>0.05) correlated with changes in body composition or hydration status during the study. The mechanism for the hormone changes in the (–) responder rowers is unclear. We speculate the decrease in concentrations of TSH and fT3 could be attributable to a lower hypothalamic-pituitary signaling action, and this is related to the decreased leptin concentrations, and could represent a possible means of energy conservation in these exercising women. Electronic Publication     

The relationship between monocarboxylate transporters 1 and 4 expression in skeletal muscle and endurance performance in athletes

The purpose of this study was to examine the relationship between skeletal muscle monocarboxylate transporters 1 and 4 (MCT1 and MCT4) expression, skeletal muscle oxidative capacity and endurance performance in trained cyclists. Ten well-trained cyclists (mean ± SD; age 24.4 ± 2.8 years, body mass 73.2 ± 8.3 kg, VO_2max 58 ± 7 ml kg⁻¹ min⁻¹) completed three endurance performance tasks [incremental exercise test to exhaustion, 2 and 10 min time trial (TT)]. In addition, a muscle biopsy sample from the vastus lateralis muscle was analysed for MCT1 and MCT4 expression levels together with the activity of citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HAD). There was a tendency for VO_2max and peak power output obtained in the incremental exercise test to be correlated with MCT1 (r = −0.71 to −0.74; P < 0.06), but not MCT4. The average power output (P _average) in the 2 min TT was significantly correlated with MCT4 (r = −0.74; P < 0.05) and HAD (r = −0.92; P < 0.01). The P _average in the 10 min TT was only correlated with CS activity (r = 0.68; P < 0.05). These results indicate the relationship between MCT1 and MCT4 as well as cycle TT performance may be influenced by the length and intensity of the task.     

Acute and cumulative effects of focused high-frequency vibrations on the endocrine system and muscle strength

The purpose of this study was to evaluate the acute and long-term effects of local high-intensity vibration (HLV, f = 300 Hz) on muscle performance and blood hormone concentrations in healthy young men. Totally 18 subjects (cV group) were studied in two sessions, either without (control) or with HLV treatment. The protocol was the same on both control and test days, except that, in the second session, subjects underwent HLV treatment. Counter-movement jumping (CMJ), maximal isometric voluntary contraction (MVC) test, and hormonal levels were measured before the procedure, immediately thereafter, and 1 h later. To assess the long-term effects of HLV, the cV group was subjected to HLV on the leg muscles for 4 weeks, and a second group (cR group, n = 18) embarked upon a resistance training program. All subjects underwent an MVC test and an isokinetic (100 deg/s) test before training, 4 weeks after training, and 2 months after the end of training. The HLV protocol significantly increased the serum level of growth hormone (GH, P < 0.05) and creatine phosphokinase (CPK, P < 0.05), and decreased the level of cortisol (P < 0.05). None of GH, CPK or testosterone levels were altered in controls. There was a significant improvement in MVC (P < 0.05). After 4 weeks, both the cV and cR groups demonstrated significant improvement in MVC and isokinetic tests (P < 0.05). This increase persisted for at least 2 months. Our results indicate that HLV influences the levels of particular hormones and improves neuromuscular performance. Our results indicate that HLV has a long-term beneficial effect comparable to that of resistance training.     

Resting serum dehydroepiandrosterone sulfate level increases after 8-week resistance training among young females

This study examined changes among young females of resting serum dehydroepiandrosterone sulfate (DHEAS) concentration after an 8-week period of resistance training. Nineteen healthy untrained young females [training group: age 18.9 (0.3) years, n=10, control group: age 19.3 (1.0) years, n=9; mean (SD)] were recruited in this study. The training group participated in an 8-week resistance training program (2 days per week on nonconsecutive days). The control group did not involve in any resistance training or regular exercise during the study period. Muscular strength, anthropometry, and resting hormonal levels were measured before and after training in both groups. Serum concentrations of DHEAS, dehydroepiandrosterone (DHEA), testosterone and cortisol were measured by radioimmunoassay. Body mass (2.4%) and lean body mass (2.4%) were significantly increased in the training group (P<0.05), but not in the control group. The training also significantly increased one-repetition maximum (1-RM) values (P<0.05). In the training group, resting concentration of serum DHEAS significantly increased after training (P<0.05). Percent change of DHEAS in the training group was greater than that of the control group (P<0.05). In the training group, the change of DHEAS level was positively correlated with the change of lean body mass during the training (r=0.61; P<0.05). Serum DHEA, testosterone and cortisol concentrations did not change in either group during the training. The dramatic increase of resting serum DHEAS concentration after training indicates that DHEAS might be an anabolic hormone marker of adaptation to resistance training among young females. Results are presented as mean (SD).     

The effect of whole-body cryostimulation on the prooxidant–antioxidant balance in blood of elite kayakers after training

The effect of whole-body cryostimulation prior to kayak training on the prooxidant-antioxidant balance was evaluated and compared to the effect of a single cryostimulation treatment in untrained men. The kayakers underwent a ten-day training cycle with pre-training daily whole-body cryostimulation for three min (temperature: –120 to –140°C) and training without cryostimulation as a control. Blood samples were obtained before and after the sixth and the tenth day of training and from the untrained men before and 20 min after cryostimulation. In untrained men cryostimulation induced an increase in the activity of superoxide dismutase (SOD) by 36% (P < 0.001) and glutathione peroxidase (GPx) by 68% (P < 0.01) in the erythrocytes and an increase in the conjugated dienes (CD) in plasma by 36% (P < 0.05) and in the erythrocytes by 71% (P < 0.001). In the kayakers comparing both types of training after the sixth day, the level of CD in plasma was 46 (P < 0.001) and 40% (P < 0.01) lower in erythrocytes, and the concentration of thiobarbituric acid-reactive substances in plasma was 24% (P < 0.05) lower with pre-training cryostimulation. After the sixth day of training with cryostimulation, SOD activity was also 47% (P < 0.001) lower, while GPx activity after the tenth day was reduced by more than 50% (P < 0.01) as compared to control training. Whole-body cryostimulation per se stimulates the generation of reactive oxygen species. Yet, the oxidative stress induced by kayak training was reduced by prior exposure to extremely low temperatures.