The effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid supplementation on muscle mass,strength, and power in resistance-trained individuals: a randomized,double-blind,placebo-controlled study

Introduction

Studies utilizing beta-hydroxy-beta-methylbutyrate (HMB) supplementation in trained populations are limited. No long-term studies utilizing HMB free acid (HMB-FA) have been conducted. Therefore, we investigated the effects of 12 weeks of HMB-FA supplementation on skeletal muscle hypertrophy, body composition, strength, and power in trained individuals. We also determined the effects of HMB-FA on muscle damage and performance during an overreaching cycle.

Methods

A three-phase double-blind, placebo- and diet-controlled randomized intervention study was conducted. Phase 1 was an 8-week-periodized resistance-training program; Phase 2 was a 2-week overreaching cycle; and Phase 3 was a 2-week taper. Muscle mass, strength, and power were examined at weeks 0, 4, 8, and 12 to assess the chronic effects of HMB-FA; and assessment of these, as well as cortisol, testosterone, and creatine kinase (CK) was performed at weeks 9 and 10 of the overreaching cycle.

Results

HMB-FA resulted in increased total strength (bench press, squat, and deadlift combined) over the 12-week training (77.1 ± 18.4 vs. 25.3 ± 22.0 kg, p < 0.001); a greater increase in vertical jump power (991 ± 168 vs. 630 ± 167 W, p < 0.001); and increased lean body mass gain (7.4 ± 4.2 vs. 2.1 ± 6.1 kg, p < 0.001) in HMB-FA- and placebo-supplemented groups, respectively. During the overreaching cycle, HMB-FA attenuated increases in CK (?6 ± 91 vs. 277 ± 229 IU/l, p < 0.001) and cortisol (?0.2 ± 2.9 vs. 4.5 ± 1.7 μg/dl, p < 0.003) in the HMB-FA- and placebo-supplemented groups, respectively.

Conclusions

These results suggest that HMB-FA enhances hypertrophy, strength, and power following chronic resistance training, and prevents decrements in performance following the overreaching.     

Effect of glutamine supplementation combined with resistance training in young adults

The purpose of this study was to assess the effect of oral glutamine supplementation combined with resistance training in young adults. A group of 31 subjects, aged 18–24 years, were randomly allocated to groups (double blind) to receive either glutamine (0.9 g·kg lean tissue mass^–1·day^–1; n=17) or a placebo (0.9 g maltodextrin·kg lean tissue mass^–1·day^–1; n=14) during 6 weeks of total body resistance training. Exercises were performed for four to five sets of 6–12 repetitions at intensities ranging from 60% to 90% 1 repetition maximum (1 RM). Before and after training, measurements were taken of 1 RM squat and bench press strength, peak knee extension torque (using an isokinetic dynamometer), lean tissue mass (dual energy X-ray absorptiometry) and muscle protein degradation (urinary 3-methylhistidine by high performance liquid chromatography). Repeated measures ANOVA showed that strength, torque, lean tissue mass and 3-methylhistidine increased with training (P<0.05), with no significant difference between groups. Both groups increased their 1 RM squat by approximately 30% and 1 RM bench press by approximately 14%. The glutamine group showed increases of 6% for knee extension torque, 2% for lean tissue mass and 41% for urinary levels of 3-methylhistidine. The placebo group increased knee extension torque by 5%, lean tissue mass by 1.7% and 3-methylhistidine by 56%. We conclude that glutamine supplementation during resistance training has no significant effect on muscle performance, body composition or muscle protein degradation in young healthy adults. Electronic Publication     

Creatine supplementation improves muscular performance in older women

Muscle power and strength decrease with age leading to reduced independence and increased health risk from falls. Creatine supplementation can increase muscle power and strength. The purpose of this study was to examine the effects of 7 days of creatine supplementation on body composition, muscular strength, and lower-body motor functional performance in older women. Thirty 58–71 year old women performed three test sessions (T1–T3) each separated by one week. Each session consisted of one repetition maximum tests for bench press and leg press, and isometric hand-grip, tandem gait, upper-body ergometer, and lower-body ergometer tests. Following T2, subjects were assigned to a creatine monohydrate (0.3 g kg body mass⁻¹ for 7 days) (CR: 63.31 ± 1.22 year, 160.00 ± 1.58 cm, 67.11 ± 4.38 kg) or a placebo (PL: 62.98 ± 1.11 year, 162.25 ± 2.09 cm, 67.84 ± 3.90 kg) supplementation group. CR significantly (P < 0.05) increased bench press (1.7 ± 0.4 kg), leg press (5.2 ± 1.8 kg), body mass (0.49 ± 0.04 kg) and fat free mass (0.52 ± 0.05) and decreased completion time on the functional tandem gait tests from T2–T3. No significant changes were found for PL on any of the measured variables. No adverse side-effects were reported by either group. Short-term creatine supplementation resulted in an increase in strength, power, and lower-body motor functional performance in older women without any adverse side effects     

The effects of short-term resistance training on endocrine function in men and women

This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group (squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5?min post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol (CORT) and growth hormone (GH). Serum TT concentrations were significantly (P?≤?0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations. Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3 when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all training phases but no significant differences were observed with training. These data illustrate that untrained individuals may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive in the early phase of strength adaptations with resistance training.     

The specificity of strength training: the effect of posture

There is a paucity of research into the importance of performing strength training exercises in postures specific to the movements they are attempting to facilitate. In addressing this question, 27 previously trained subjects were randomly allocated into heavy weight training and control groups. The weight training group performed 4–6 sets of 6–10 repetitions of the squat and bench press lifts twice a week for 8 weeks. Prior to and after the training period the following tests were conducted: bench press throw at 30% of maximal load, vertical jump, maximal squat and bench press lifts, push-up test performed over a force platform, 40-m sprint, 6-s cycle, and isokinetic tests assessing upper and lower body musculature in varying actions. The results supported the concept that posture is important in training as those exercises conducted in similar postures to the training recorded the greatest improvement in performance. For example, after completion of the training the weight training subjects significantly increased by approximately 12% the maximal load lifted in the bench press exercise and the peak torque in the isokinetic bench press test. However, performance in the isokinetic horizontal arm adduction test was not significantly changed. We speculate that the phenomenon of posture specificity may, at least in part, be caused by the differing postures altering the neural input to the musculature. The results stress the importance of selecting exercises in which the posture closely resembles that of the movements they are attempting to facilitate.     

Effects of creatine monohydrate ingestion in sedentary and weight-trained older adults

To investigate the effects of an oral creatine supplementation in older adults, 32 elderly subjects (67–80 years; 16 females, 16 males) were randomly assigned to four equivalent subgroups (control-creatine; control-placebo; trained-creatine; trained-placebo) based on whether or not they took part in an 8-week strength training programme and an 8-week oral creatine monohydrate creatine supplementation programme. The strength training programme consisted of three sets of eight repetitions at 80% of one-repetition maximum, for leg press, leg extension and chest press, 3 days a week. The 52-day supplementation programme consisted of 20 g of creatine monohydrate (or glucose) and 8 g of glucose per day for the initial 5 days followed by 3 g of creatine monohydrate (or glucose), and 2 g of glucose per day. Prior to and after the training and supplementation periods, body mass, body fat, lower limb muscular volume, 1-, 12-repetitions maxima and isometric intermittent endurance tests for leg press, leg extension and chest press were determined. In all groups, no significant changes in anthropometric parameters were observed. For all movements, the increases in 1- and 12-repetitions maxima were greater (P < 0.02) in trained than control subjects. No significant interactions (supplementation/training/time) were observed for the 1-, 12-repetitions maxima, and the isometric intermittent endurance, whatever the movement considered. We conclude that oral creatine supplementation does not provide additional benefits for body composition, maximal dynamical strength, and dynamical and isometric endurances of healthy elderly subjects, whether or not it is associated with an effective strength training.     

The effects of supplementation with 19-nor-4-androstene-3,17-dione and 19-nor-4-androstene-3,17-diol on body composition and athletic performance in previously weight-trained male athletes

The purpose of this study was to determine the effects of 8 weeks of norsteroid supplementation on body composition and athletic performance in previously weight-trained males. Subjects were weight and percent body fat matched and randomly assigned to receive either 100 mg of 19-nor-4-androstene-3,17-dione (N-dione) and 56 mg of 19-nor-4-androstene-3,17-diol (N-diol; 156 mg total norsteroid per day), or a placebo (a multivitamin). Each subject participated in resistance training 4 days/week for the duration of the study. Body composition was assessed via dual-energy X-ray absorptiometry. Circumference measures were taken of a relaxed and flexed arm (maximum circumference of the arm), waist (level of umbilicus), and thigh (15 cm proximal to the patella). Strength was determined with a one-repetition maximum bench press, while force and power were determined with a dumbbell bench press (60% body weight) on a Stratec Galileo force platform. Profile of mood states scores were evaluated for vigor and fatigue. There were no significant changes in any of the parameters measured. In conclusion, low-dose supplementation with N-dione and N-diol does not appear to alter body composition, exercise performance, or mood states. Electronic Publication     

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.     

Long-term creatine supplementation improves muscular performance during resistance training in older women

This study examined the effects of long-term creatine supplementation combined with resistance training (RT) on the one-repetition maximum (1RM) strength, motor functional performance (e.g., 30-s chair stand, arm curl, and getting up from lying on the floor tests) and body composition (e.g., fat-free mass, muscle mass, and % body fat using DEXA scans) in older women. Eighteen healthy women (64.9 ± 5.0 years) were randomly assigned in a double-blind fashion to either a creatine (CR, N = 9) or placebo (PL, N = 9) group. Both groups underwent a 12-week RT program (3 days week^?1), consuming an equivalent amount of either creatine (5.0 g day^?1) or placebo (maltodextrin). After 12 week, the CR group experienced a greater (P < 0.05) increase (Δ%) in training volume (+164.2), and 1RM bench press (+5.1), knee extension (+3.9) and biceps curl (+8.8) performance than the PL group. Furthermore, CR group gained significantly more fat-free mass (+3.2) and muscle mass (+2.8) and were more efficient in performing submaximal-strength functional tests than the PL group. No changes (P > 0.05) in body mass or % body fat were observed from pre- to post-test in either group. These results indicate that long-term creatine supplementation combined with RT improves the ability to perform submaximal-strength functional tasks and promotes a greater increase in maximal strength, fat-free mass and muscle mass in older women.     

Creatine supplementation post-exercise does not enhance training-induced adaptations in middle to older aged males

Purpose

The present study evaluated the effects of creatine monohydrate (CrM) consumption post-exercise on body composition and muscle strength in middle to older males following a 12-week resistance training program.

Methods

In a double-blind, randomized trial, 20 males aged between 55 and 70 years were randomly assigned to consume either CrM-carbohydrate (CHO) [20 g days^?1 CrM + 5 g days^?1 CHO × 7 days, then 0.1 g kg^?1 CrM + 5 g CHO on training days (average dosage of ~8.8 g)] or placebo CHO (20 g days^?1 CHO × 7 days, then 5 g CHO on training days) while participating in a high intensity resistance training program [3 sets × 10 repetitions at 75 % of 1 repetition maximum (1RM)], 3 days weeks^?1 for 12 weeks. Following the initial 7-day “loading” phase, participants were instructed to ingest their supplement within 60 min post-exercise. Body composition and muscle strength measurements, blood collection and vastus lateralis muscle biopsy were completed at 0, 4, 8 and 12 weeks of the supplement and resistance training program.

Results

A significant time effect was observed for 1RM bench press (p = 0.016), leg press (p = 0.012), body mass (p = 0.03), fat-free mass (p = 0.005) and total myofibrillar protein (p = 0.005). A trend for larger muscle fiber cross-sectional area in the type II fibers compared to type I fibers was observed following the 12-week resistance training (p = 0.08). No supplement interaction effects were observed.

Conclusion

Post-exercise ingestion of creatine monohydrate does not provide greater enhancement of body composition and muscle strength compared to resistance training alone in middle to older males.     

Creatine supplementation does not enhance submaximal aerobic training adaptations in healthy young men and women

The benefits of dietary creatine supplementation on muscle performance are generally related to an increase in muscle phosphocreatine content. However, creatine supplementation may benefit endurance sports through increased glycogen re-synthesis following exercise. This study investigated the effect of creatine supplementation on muscle glycogen content, submaximal exercise fuel utilisation and endurance performance following 4 weeks of endurance training. Thirteen healthy, physically active, non-vegetarian subjects volunteered to take part and completed the study. Subjects were supplemented with either creatine monohydrate (CREAT, n = 7) or placebo-maltodextrin (CON, n = 6). Submaximal fuel utilisation and endurance performance were assessed before and after a 4 week endurance training program. Muscle biopsies were also collected before and following training for assessment of muscle creatine and glycogen content. Training increased quadriceps glycogen content to the same degree (∼20%) in both groups (P = 0.04). There was a significant training effect on submaximal fuel utilisation and improved endurance performance. However, there was no significant treatment effect of creatine supplementation. Creatine supplementation does not effect metabolic adaptations to endurance training.     

The Effects of Low-Dose Creatine Supplementation Versus Creatine Loading in Collegiate Football Players

OBJECTIVE: To compare the effects of low doses of creatine and creatine loading on strength, urinary creatinine concentration, and percentage of body fat. DESIGN AND SETTING: Division IA collegiate football players took creatine monohydrate for 10 weeks during a sport-specific, periodized, off-season strength and conditioning program. One-repetition maximum (1-RM) squat, urinary creatinine concentrations, and percentage of body fat were analyzed. SUBJECTS: Twenty-five highly trained, Division IA collegiate football players with at least 1 year of college playing experience. MEASUREMENTS: We tested strength with a 1-RM squat exercise before, during, and after creatine supplementation. Percentage of body fat was measured by hydrostatic weighing before and after supplementation. Urinary creatinine concentration was measured via light spectrophotometer at 0, 1, 3, 7, 14, 21, 28, 35, 42, 48, 56, and 63 days. An analysis of variance with repeated measures was computed to compare means for all variables. RESULTS: Creatine supplementation had no significant group, time, or interaction effects on strength, urinary creatinine concentration, or percentage of body fat. However, significant time effects were found for 1-RM squat and fat-free mass in all groups. CONCLUSIONS: Our data suggest that creatine monohydrate in any amount does not have any beneficial ergogenic effects in highly trained collegiate football players. However, a proper resistance training stimulus for 10 weeks can increase strength and fat-free mass in highly trained athletes.     

Effect of high versus low-velocity resistance training on muscular fitness and functional performance in older men

This study investigated the effect of a 10-week power training (PT) program versus traditional resistance training (TRT) on functional performance, and muscular power and strength in older men. Twenty inactive volunteers (60–76 years old) were randomly assigned to a PT group (three 8–10 repetition sets performed as fast a possible at 60% of 1-RM) or a TRT group (three 8–10 repetition sets with 2–3 s contractions at 60% of 1-RM). Both groups exercised 2 days/week with the same work output. Outcomes were measured with the Rikli and Jones functional fitness test and a bench and leg press test of maximal power and strength (1-RM). Significant differences between and within groups were analyzed using a two-way analysis of variance (ANOVA). At 10 weeks there was a significantly (P < 0.05) greater improvement in measures of functional performance in the PT group. Arm curling improved by 50 versus 3% and a 30 s chair-stand improved by 43 versus 6% in the PT and TRT groups, respectively. There was also a significantly greater improvement in muscular power (P < 0.05) in the PT group. The bench press improved by 37 versus 13%, and the leg press by 31 and 8% in the PT and TRT groups, respectively. There was no significant difference between groups in improved muscular strength. It appears that in older men there may be a significantly greater improvement in functional performance and muscular power with PT versus low velocity resistance training.     

Effects of creatine monohydrate supplementation during combined strength and high intensity rowing training on performance.

This study investigated the effect of creatine monohydrate (Cr) supplementation on performance and training volume in rowers. Twenty-two rowers trained with continuous and interval rowing and resistance training 4 and 2 days/week, respectively, for 6 weeks. Cr supplementation consisted of a 5-day load (0.3 g/kg(-1) x day(-1)) followed by a 5-week maintenance dose (0.03 g/kg(-1) x day(-1)) while training. Five days of Cr loading did not change body composition, repeated interval rowing performance, 2,000-m rowing times, or strength performance. Five additional weeks of training with a maintenance dose of Cr or placebo significantly improved body composition, VO2max, 2,000-m rowing times, repeated power interval performance, and strength to a similar extent in both groups. Subjects training with Cr did not perform more repetitions per set of strength exercise nor produce or maintain higher power outputs during repeated rowing sessions. Cr supplementation did not increase performance or training volume over a placebo condition in rowers that performed a combined high intensity rowing and strength program.     

Skeletal muscle metabolism during short duration high-intensity exercise: influence of creatine supplementation

Seven male subjects performed repeated bouts of high-intensity exercise, on a cycle ergometer, before and after 6 d of creatine supplementation (20 g Cr H₂O day^-1). The exercise protocol consisted of five 6-s exercise periods performed at a fixed exercise intensity, interspersed with 30-s recovery periods (Part I), followed (40 s later) by one 10 s exercise period (Part II) where the ability to maintain power output was evaluated. Muscle biopsies were taken from m. vastus lateralis at rest, and immediately after (i) the fifth 6 s exercise period in Part I and (ii) the 10 s exercise period in Part II. In addition, a series of counter movement (CMJ) and squat (SJ) jumps were performed before and after the administration period. As a result of the creatine supplementation, total muscle creatine [creatine (Cr) + phosphocreatine (PCr)] concentration at rest increased from (mean + SEM) 128.7 (4.3) to 151.5 (5.5)mmolkg^_1 dry wt (P < 0.05). This was accompanied by a 1.1 (0.5) kg increase in body mass (P < 0.05). After the fifth exercise bout in Part I of the exercise protocol, PCr concentration was higher [69.7 (2.3) vs. 45.6 (7.5) mmol kg“‘ dry wt, P < 0.05], and muscle lactate was lower [26.2 (5.5) vs. 44.3 (9.9) mmol kg”¹ dry wt, P < 0.05] after vs. before supplementation. In Part II, after creatine supplementation, subjects were better able to maintain power output during the 10-s exercise period (P < 0.05). There was no change in jump performance as a result of the creatine supplementation (P > 0.05). These findings show that enhanced fatigue resistance during short duration high-intensity exercise following creatine supplementation is associated with a greater availability of PCr and a lower accumulation of lactate in the muscle. The finding that jump performance was not enhanced suggests that short-term creatine feeding does not influence peak power output.     

The effect of varying the time of concentric and eccentric muscle actions during resistance training on skeletal muscle adaptations in women

This study investigated the effect of manipulating the time to complete both the concentric (CON) and eccentric (ECC) muscle actions during resistance training on strength, skeletal muscle properties and cortisol in women. Twenty-eight women (mean ± SE age = 24.3 ± 1.1 year) with strength training experience completed three training sessions per week for 9 weeks. Two sets of four lower body exercises (leg press, parallel squat, knee extension and knee flexion) were completed using 6–8 RM intensity. The long CON (LC) group performed the CON action for 6 s and the ECC action for 2 s, while the long ECC (LE) group completed the CON and ECC phases for 2 and 6 s, respectively. Both groups experienced significant increases in leg press CON only, ECC only and combined ECC and CON maximal strength (1 RM). Immunohistochemical analyses demonstrated that both types I and IIA vastus lateralis fibre areas significantly increased following LC training while only type I fibre area increased following LE training. There was a decrease in MHCIId(x) with a concomitant increase in MHCIIa (P < 0.05) in both groups. Twenty-four hour urinary cortisol significantly increased after LC training only. It was concluded that LC resistance training was more effective than LE for increasing both types I and IIA fibre area and cortisol when time under tension and intensity of muscle actions were matched between the two modes of resistance training in young healthy women.     

A comparison of strength and muscle mass increases during resistance training in young women

Strength gains with resistance training are due to muscle hypertrophy and nervous system adaptations. The contribution of either factor may be related to the complexity of the exercise task used during training. The purpose of this investigation was to measure the degree to which muscle hypertrophy contributes to gains in strength during exercises of varying complexity. Nineteen young women resistance trained twice a week for 20 weeks, performing exercises designed to provide whole-body training. The lean mass of the trunk, legs and arms was measured by dual energy x-ray absorptiometry and compared to strength gains (measured as the 1-repetition maximum) in bench press, leg press and arm curl exercises, pre-, mid- (10 weeks) and post-training. No changes were found in a control group of ten women. For the exercise group, increases in bench press, leg press and arm curl strength were significant from pre- to mid-, and from mid- to post-training (P P?相似文献   

Hormonal responses to training and its tapering off in competitive swimmers: relationships with performance

During a winter training season, the effects of 12 weeks of intense training and 4 weeks of tapering off (taper) on plasma hormone concentrations and competition performance were investigated in a group of highly trained swimmers (n = 8). Blood samples were collected and the swimmers performed their speciality in competition at weeks 10 (mid-season), 22 (pre-taper) and 26 (post-taper). No statistically significant changes were observed in the concentrations of total testosterone (TT), non-sex hormone binding globulin-boundtestosterone (NSBT), cortisol (C), luteinising hormone, thyroid stimulating hormone, triiodothyronine, thyroxine plasma catecholamines, creatine kinase and ammonia during training and taper. Mid-season NSBT: C ratio and the amount of training were statistically related (r = 0.82,P < 0.05). Competition performance slightly declined during intense training [0.52 (SD 2.51) %, NS] and improved during taper [2.32 (SD 1.69)%,P < 0.01]. Changes in performance during training and taper correlated with changes in ratios TT: C (r = 0.86,P < 0.01andr = 0.81,P < 0.05, respectively) and NSBT: C (r = 0.77,P < 0.05 andr = 0.76,P < 0.05, respectively). In summary, these results showed that the monitored plasma hormones and metabolic indices were unaltered by 12 weeks of intense training and 4 weeks of taper. The TT: C and NSBT: C ratios, however, appeared to be effective markers of the swimmers' performance capacities throughout the training season.     

Similar hormonal responses to concentric and eccentric muscle actions using relative loading

Conventional resistance exercise is performed using sequential concentric (CON) and eccentric (ECC) contractions, utilizing the same muscle load. Thus, relative to maximal CON and ECC resistance, the ECC contraction is loaded to a lesser degree. We have recently shown that at the same absolute load, CON contractions are associated with greater growth hormone (GH) but similar total testosterone (TT) and free testosterone (FT) responses compared with ECC contractions and attributed the larger GH response to greater relative CON loading. In the present study, we have examined the same endocrine parameters to six different upper and lower body exercises using relative loading rather than absolute loading, hypothesizing that GH responses would be similar for CON and ECC actions, but TT and FT responses would be greater after ECC contractions. Seven young men with recreational weight training experience completed an ECC and CON muscle contraction trial on two different occasions in a counterbalanced fashion. The exercises consisted of four sets of 10 repetitions of lat pull-down, leg press, bench press, leg extension, military press, and leg curl exercises at 65% of an ECC or CON 1–RM with 90 s between sets and exercises. CON and ECC actions were performed at the same speed. ECC 1-RMs were considered to be 120% of the CON 1-RM for the same exercise. Blood samples were collected before, immediately after, and 15 min after the exercise. GH significantly increased across both trials but was not different between the two trials. Total testosterone was not significantly altered in response to either trial; however, free testosterone concentrations increased in response to both ECC and CON trials. Data suggest that CON and ECC muscle contractions produce similar GH, T, and free testosterone responses with the same relative loading.     

Effects of vibration and resistance training on neuromuscular and hormonal measures

The aim was to study whether whole body vibration (WBV) combined with conventional resistance training (CRT) induces a higher increase in neuromuscular and hormonal measures compared with CRT or WBV, respectively. Twenty-eight young men were randomized in three groups; squat only (S), combination of WBV and squat (S+V) and WBV only (V). S+V performed six sets with eight repetitions with corresponding eight repetition maximum (RM) loads on the vibrating platform, whereas S and V performed the same protocol without WBV and resistance, respectively. Maximal isometric voluntary contraction (MVC) with electromyography (EMG) measurements during leg press, counter movement jump (CMJ) measures (mechanical performance) including jump height, mean power (P _mean), peak power (P _peak) and velocity at P _peak (V _ppeak) and acute hormonal responses to training sessions were measured before and after a 9-week training period. ANOVA showed no significant changes between the three groups after training in any neuromuscular variable measured [except P _mean, S higher than V (P<0.05)]. However, applying t tests within each group revealed that MVC increased in S and S+V after training (P<0.05). Jump height, P _mean and P _peak increased only in S, concomitantly with increased V _ppeak in all groups (P<0.05). Testosterone increased during training sessions in S and S+V (P<0.05). Growth hormone (GH) increased in all groups but S+V showed higher responses than S and V (P<0.05). Cortisol increased only in S+V (P<0.05). We conclude that combined WBV and CRT did not additionally increase MVC and mechanical performance compared with CRT alone. Furthermore, WBV alone did not increase MVC and mechanical performance in spite of increased GH.