A comparison of the immediate effects of resistance, aerobic, and concurrent exercise on postexercise hypotension

A comparison of the immediate effects of resistance, aerobic, and concurrent exercise on postexercise hypotension. The influence of resistance exercise (RE), aerobic exercise (AE), and concurrent exercise (CE) on postexercise hypotension (PEH) is not known. We investigated the immediate blood pressure (BP) lowering effects of exercise after RE, AE, and CE sessions among healthy subjects. Twenty-one men (20.7 ± 0.7 years) performed 4 experimental sessions each in a within-subject design: control (CTL-seated rest for 60 minutes), RE (3 sets at 80% 1RM for 8 exercises, including upper and lower limbs), AE (7-minutes warm-up followed by 50 minutes of cycle ergometer exercise at 65% VO?peak and 3-minute cooldown), and CE (2 sets at 80% 1RM for 6 exercises among those which composed the RE session, plus 20 minutes of cycle ergometer exercise at 65% VO?peak, 7-minute warm-up and 3-minute cooldown, exactly in this order). The total duration of each exercise session was approximately 60 minutes. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were assessed by ambulatory monitoring at rest (20 minutes) and every 10 minutes after the exercise during 120 minutes while in the laboratory. The duration of the decrease in SBP was longer after AE and CE (120 minutes) compared to RE (80 minutes); and for DBP after AE (50 minutes) compared to CE (40 minutes) and RE (20 minutes) (p < 0.05). The magnitude of the decrease in SBP and DBP was similar after all exercise sessions and significantly different from CTL (p < 0.05) (SBP: RE = 4.1 ± 2.0 mm Hg, AE = 6.3 ± 1.3 mm Hg, CE = 5.1 ± 2.2 mm Hg; DBP: RE = 1.8 ± 1.1 mm Hg, AE = 1.8 ± 1.0 mm Hg, CE = 1.6 ± 0.6 mm Hg). It was concluded that exercise sessions combining aerobic and resistance activities are as effective as AE sessions and more effective than RE sessions to promote PEH.     

Time course of strength and power recovery after resistance training with different movement velocities

The purpose of this study was to evaluate the time course of strength and power recovery after a single bout of strength training designed with fast and slow contraction velocities. Nineteen male subjects were randomly divided into 2 groups: the slow-velocity contraction (SV) group and the fast velocity contraction (FV) group. Resistance training protocols consisted of 5 sets of 12 repetition maximum (5 × 12RM) with 50 seconds of rest between sets and 2 minutes between exercises. Contraction velocity was controlled by the execution time for each repetition (SV-6 seconds to complete concentric and eccentric phases and for FV-1.5 seconds). Leg Press 45° 1RM (LP 1RM), horizontal countermovement jump (HCMJ), and right thigh circumference (TC) were accessed in 6 distinct moments: base (1 week before exercise), 0 (immediately after exercises), 24, 48, 72, and 96 hours after exercise protocol. The SV and FV presented significant LP 1RM decrements at 0, and these were still evident 24-48 hours postexercise. The magnitude of decline was significantly (p < 0.05) higher for FV. The SV and FV presented significant HCMJ decrements at 0, but only for FV were these still evident 24-72 hours postexercise. The SV and FV presented significant TC increments at 0, and these were still evident 24-48 hours postexercise for SV but for FV it continued up to 96 hours. The magnitude of increase was significantly (p < 0.05) higher for FV. In conclusion, the fast contraction velocity protocol resulted in greater decreases in LP 1RM and HCMJ performance, when compared with slow velocity. The results lead us to interpret that this variable may exert direct influence on acute muscle strength and power generation capacity.     

The effect of 5, 10, and 20 repetition maximums on the recovery of voluntary and evoked contractile properties

Maximal strength training has been reported to emphasize neural adaptations. The main objective of this study was to detect differences in muscle activation between 5, 10, and 20 repetition maximum (RM) sets. Fourteen subjects performed elbow flexion with 5, 10, and 20RM. Subjects were tested for maximum isometric force (maximal voluntary contraction [MVC]), twitch amplitude (peak twitch [Pt]), time to peak twitch (TPT), half relaxation time ((1/2) RT), electromyography (EMG), and muscle activation (interpolated twitch). Subjects were tested preexercise and 30 seconds, 1, 2, and 3 minutes postexercise. There were no significant differences in MVC, muscle activation, or antagonist/agonist EMG after 5, 10, or 20RM. However, greater RM did have a greater detrimental effect on twitch properties than fewer RM. Peak twitch was significantly (p = 0.004) less (32.08%) for the 20 than for the 5RM, whereas TPT shortened (p < 0.05) by 7.3 and 11.1% with 10 and 20RM vs. 5RM, respectively. Half relaxation time at 20RM was shortened (p < 0.05) by 20.6 and 25.4% compared with that at 5 and 10RM, respectively. MVC, muscle activation, and temporal twitch properties did not recover within 3 minutes of recovery. In conclusion, whereas 5RM did not produce greater muscle inactivation, twitch contractile properties were affected to a greater degree by a higher number of RM.     

Short-term effects of selected exercise and load in contrast training on vertical jump performance

The present study examined the short-term effects of loaded half squats (HSs) and loaded jump squats (JSs) with low and moderate loads on the squat jump (SJ) and the countermovement jump (CMJ) performance using a contrast training approach. Ten men (mean +/- SD age, 23 +/- 1.8 years) performed the HS and JS exercises twice with loads of 30% of 1 repetition maximum (1RM) (HS30% and JS30%, respectively) and 60% of 1RM (HS60% and JS60%, respectively). On each occasion, 3 sets of 5 repetitions with 3 minutes of rest were performed as fast as possible. Vertical jump performance was measured before exercise, 1 minute after each set, and at the fifth and 10th minutes of recovery. The CMJ increased significantly after the first and second set (3.9%; p < 0.05) compared with preexercise values following the JS30% protocol and 3.3% after the second and third sets of the JS60% protocol. Following the HS60% protocol, CMJ increased after the first and the second sets (3.6%; p < 0.05) compared with preexercise values, whereas SQ increased only after the first set (4.9%; p < 0.05) in this condition. These data show that contrast loading with the use of low and moderate loads can cause a short-term increase in CMJ performance. The applied loads do not seem to present different short-term effects after loaded JSs. When the classic form of dynamic HS exercise is performed, however, at least a moderate load (60% of 1RM) needs to be applied.     

Salivary testosterone and cortisol responses in professional rugby players after four resistance exercise protocols

The acute response of free salivary testosterone (T) and cortisol (C) concentrations to four resistance exercise (RE) protocols in 23 elite men rugby players was investigated. We hypothesized that hormonal responses would differ among individuals after four distinct RE protocols: four sets of 10 repetitions (reps) at 70% of 1 repetition maximum (1RM) with 2 minutes' rest between sets (4 x 10-70%); three sets of five reps at 85% 1RM with 3 minutes' rest (3 x 5-85%); five sets of 15 reps at 55% 1RM with 1 minute's rest (5 x 15-55%); and three sets of five reps at 40% 1RM with 3 minutes' rest (3 x 5-40%). Each athlete completed each of the four RE protocols in a random order on separate days. T and C concentrations were measured before exercise (PRE), immediately after exercise (POST), and 30 minutes post exercise (30 POST). Each protocol consisted of four exercises: bench press, leg press, seated row, and squats. Pooled T data did not change as a result of RE, whereas C declined significantly. Individual athletes differed in their T response to each of the protocols, a difference that was masked when examining the pooled group data. When individual data were retrospectively tabulated according to the protocol in which each athlete showed the highest T response, a significant protocol-dependent T increase for all individuals was revealed. Therefore, RE induced significant individual, protocol-dependent hormonal changes lasting up to 30 minutes after exercise. These individual responses may have important ramifications for modulating adaptation to RE and could explain the variability often observed in studies of hormonal response to RE.     

Significant strength gains observed in rugby players after specific resistance exercise protocols based on individual salivary testosterone responses

Our previous work has demonstrated that professional athletes show protocol-dependent variability in salivary testosterone (T) responses to resistance exercise (RE). The current study examines the consistency and functional outcomes of prescribing a RE regimen based on T response. We hypothesized that prescribing an individual-specific RE protocol based on T response would enhance weight training gains. Sixteen amateur rugby players [(mean +/- SD) age: 20 +/- 2 years; height: 181.5 +/- 8.2 cm; weight: 94.2 +/- 11.1 kg] were characterized by their maximal (Tmax) and minimal (Tmin) T response to four RE protocols: four sets of 10 repetitions (reps) at 70% of one repetition maximum (1RM) with 2 minutes' rest between sets (4 x10-70%); three sets of five reps at 85% 1RM with 3 minutes' rest (3 x 5-85%); five sets of 15 reps at 55% of 1RM with 1 minute's rest (5 x 15-55%); and three sets of 5 reps at 40% 1RM with 3 minutes' rest (3 x 5-40%). Eight athletes then performed a 3-week training block performing only their Tmax protocol. The remaining eight only performed Tmin. After 3 weeks, the athletes were retested on the RE protocols and then crossed over and performed the alternate 3-week training block. All 16 athletes showed significant increases in estimated bench and leg press 1RM strength and bodyweight while performing Tmax. When Tmin was performed, 75% of athletes showed either no change or a significant decline in 1RM performance. Consistent protocol-responses over the experimental period were seen for both the Tmax and Tmin protocols in 12 of 16 athletes. Thus, a relationship between an individual's biologically available T response to RE and enhanced functional gains is reported.     

Changes in arterial distensibility and flow-mediated dilation after acute resistance vs. aerobic exercise

Previous research has shown significantly lower arterial distensibility (AD) after resistance exercise (RE) yet higher AD after aerobic exercise (AE). These changes may be related to exercise-induced differences in vasodilatory capacity. The purpose of this study was to investigate the vasodilatory and AD responses to acute AE and RE. Forearm blood flow (FBF) during reactive hyperemia (RH) was assessed before and 60 minutes after exercise, whereas aortic and femoral pulse wave velocity was measured as an index of arterial stiffness pre, 40, and 60 minutes after an acute bout of AE (30-minute leg ergometry at 65% of VO2peak) and RE (3 sets, 10 reps; upper and lower body at 65% 1 repetition maximum) in 10 male subjects (24.9 ± 0.86 years). Area under the curve (AUC) was employed to determine differences in flow. After the intervention, we found that central pulse wave velocity decreased 8% after AE and remained depressed at this level through 60 minutes of observation, whereas RE increased central pulse wave velocity 9.8% from pre to 40 and 60 minutes postexercise. Area under the curve for FBF-RH significantly increased 38% after RE, yet there was no significant change after AE. Forearm vasodilatory capacity increased after acute RE but not after acute AE. This suggests that changes in AD may be disassociated from changes in vasodilatory capacity after acute exercise. Further, in a direct comparison of RE vs. AE, we have shown that RE has greater increases in limb blood flow and augments postexercise hypotension greater at 40 minutes postexercise when compared to AE.     

Effect of unilateral and bilateral resistance exercise on maximal voluntary strength,total volume of load lifted,and perceptual and metabolic responses

The present study investigated the effect of unilateral and bilateral resistance exercise (RE) on maximal voluntary strength, total volume of load lifted (TVLL), rating of perceived exertion (RPE) and blood lactate concentration of resistance-trained males. Twelve healthy men were assessed for the leg extension one-repetition maximum (1RM) strength using bilateral and unilateral contractions. Following this assessment, an RE session (3 sets of repetitions to failure) was conducted with bilateral and unilateral (both limbs) contractions using a load of 50% 1RM. The TVLL was calculated by the product of the number of repetitions and the load lifted per repetition. RPE and blood lactate were measured before, during and after each set. Session RPE was measured 30 minutes after RE sessions. There was a significant difference in the bilateral (120.0±11.9) and unilateral (135.0±20.2 kg) 1RM strength (p < 0.05). The TVLL was similar between both RE sessions. Although the repetitions decreased with each successive set, the total number of repetitions completed in the bilateral protocol (48) was superior to the unilateral (40) protocol (p < 0.05). In both bouts, RPE increased with each subsequent set whilst blood lactate increased after set 1 and thereafter remained stable (p < 0.05). The RPE and lactate responses were not significantly different between both sessions. In conclusion, a bilateral deficit in leg extension strength was confirmed, but the TVLL was similar between both RE sessions when exercising to voluntary fatigue. This outcome could be attributed to the number of repetitions completed in the unilateral RE bout. The equal TVLL would also explain the similar perceptual and metabolic responses across each RE session.     

The combined effects of exercise and ingestion of a meal replacement in conjunction with a weight loss supplement on body composition and fitness parameters in college-aged men and women

This study was performed to evaluate the combined effect of a meal replacement and an alleged weight loss supplement (WLS) on body composition, fitness parameters, and clinical health in moderately overweight college-aged men and women. Body mass, bench press 1 repetition maximum (1RM), leg press 1RM, body composition, V(O2)max, fasting glucose (GLU), and lipid panels were evaluated before (T1) and after (T2) 8 weeks of combined resistance training (RT) and cardiovascular training (CVT). After T1, subjects were randomly assigned in a double-blind fashion to either the WLS (6 men, 7 women; 21 ± 5 years, 168 ± 8 cm, 75.4 ± 12.7 kg, 31.6 ± 7.7%BFAT) or placebo (PLA: 6 men, 6 women; 22 ± 4 years, 174 ± 9 cm, 84.1 ± 8.8 kg, 30.2 ± 5.6%BFAT) group. Both groups performed 3 d · wk(-1) of combined progressive RT (2 × 12 reps of 8 exercises at 75-80% 1RM) and CVT (30 minutes on a cycle ergometer at 70-85% heart rate reserve). Subjects consumed 4 capsules per day and a once-daily meal replacement throughout the protocol. Percent body fat, bench press 1RM, and leg press 1RM significantly improved (p < 0.05) in both groups. Blood GLU (G × T; p = 0.048) improved in WLS and systolic blood pressure (SBP) approached significance (G × T; p = 0.06) in the WLS group. Follow-up analysis of SBP revealed a significant within-group decrease in the WLS group, whereas no within-group changes were found for either group for GLU. Practically speaking, daily supplementation with a meal replacement and a thrice weekly exercise program can increase fitness levels and improve body composition, whereas adding a thermogenic substance provides no additional benefit over fitness or body composition changes but may favorably alter serum markers of clinical health.     

Early-phase neuroendocrine responses and strength adaptations following eccentric-enhanced resistance training

The purpose of this study was to evaluate the early-phase muscular performance adaptations to 5 weeks of traditional (TRAD) and eccentric-enhanced (ECC+) progressive resistance training and to compare the acute postexercise total testosterone (TT), bioavailable testosterone (BT), growth hormone (GH), and lactate responses in TRAD- and ECC+-trained individuals. Twenty-two previously untrained men (22.1 +/- 0.8 years) completed 1 familiarization and 2 baseline bouts, 15 exercise bouts (i.e., 3 times per week for 5 weeks), and 2 postintervention testing bouts. Anthropometric and 1 repetition maximum (1RM) measurements (i.e., bench press and squat) were assessed during both baseline and postintervention testing. Following baseline testing, participants were randomized into TRAD (4 sets of 6 repetitions at 52.5% 1RM) or ECC+ (3 sets of 6 repetitions at 40% 1RM concentric and 100% 1RM eccentric) groups and completed the 5-week progressive resistance training protocols. During the final exercise bout, blood samples acquired at rest and following exercise were assessed for serum TT, BT, GH, and blood lactate. Both groups experienced similar increases in bench press (approximately 10%) and squat (approximately 22%) strength during the exercise intervention. At the conclusion of training, postexercise TT and BT concentrations increased (approximately 13% and 21%, respectively, p < 0.05) and GH concentrations increased (approximately 750-1200%, p < 0.05) acutely following exercise in both protocols. Postexercise lactate accumulation was similar between the TRAD (5.4 +/- 0.4) and ECC+ (5.6 +/- 0.4) groups; however, the ECC+ group's lactate concentrations were significantly lower than those of the TRAD group 30 to 60 minutes into recovery. In conclusion, TRAD training and ECC+ training appear to result in similar muscular strength adaptations and neuroendocrine responses, while postexercise lactate clearance is enhanced following ECC+ training.     

Effect of resistance exercise on muscle steroidogenesis

Circulating testosterone is elevated acutely following resistance exercise (RE) and is an important anabolic hormone for muscle adaptations to resistance training. The purpose of this study was to examine the acute effect of heavy RE on intracrine muscle testosterone production in young resistance-trained men and women. Fifteen young, highly resistance-trained men (n = 8; 21 +/- 1 yr, 175.3 +/- 6.7 cm, 90.8 +/- 11.6 kg) and women (n = 7; 24 +/- 5 yr, 164.6 +/- 6.7 cm, 76.4 +/- 15.6 kg) completed 6 sets of 10 repetitions of Smith machine squats with 80% of their 1-repetition maximum. Before RE and 10 and 70 min after RE, muscle biopsies were obtained from the vastus lateralis. Before RE, after 3 and 6 sets of squats, and 5, 15, 30, and 70 min into recovery from RE, blood samples were obtained using venipuncture from an antecubital vein. Muscle samples were analyzed for testosterone, 17beta-hydroxysteroid dehydrogenase (HSD) type 3, and 3beta-HSD type 1 and 2 content. Blood samples were analyzed for glucose and lactate concentrations. No changes were found for muscle testosterone, 3beta-HSD type 1 and 2, and 17beta-HSD type 3 concentrations. However, a change in protein migration in the Bis-Tris gel was observed for 17beta-HSD type 3 postexercise; this change in migration indicated an approximately 2.8 kDa increase in molecular mass. These findings indicate that species differences in muscle testosterone production may exist between rats and humans. In humans, muscle testosterone concentrations do not appear to be affected by RE. This study expands on the current knowledge obtained from animal studies by examining resting and postexercise concentrations of muscle testosterone and steroidogenic enzymes in humans.     

Resistance and aerobic exercise: the influence of mode on the relationship between IL-6 and glucose tolerance in young men who are obese

Regular exercise lowers indicators of disease risk including some inflammatory cytokines; however, the relationship between different modes of acute exercise, cytokine levels, and subsequent glucose tolerance is unclear. The purpose was to determine the effects of resistance (RES) and aerobic (AER) exercises on interleukin-6 (IL-6) and its association with glucose tolerance 24 hours after exercise. After testing for 1 repetition maximum (1RM) and VO2peak, 10 obese (body mass index > 30 kg · m(-2)), untrained men aged 18-26 years completed 3 protocols: 60 minutes of RES, AER, and a resting (CON) condition. The RES was 2 sets of 8 repetitions and a third set to fatigue at 80% 1RM of 8 lifts using all major muscle groups. The AER was 60 minutes of cycling at 70% of VO2peak. On day 1, subjects completed the 60-minute exercise or resting protocol, and on day 2, they completed an oral glucose tolerance test (OGTT). Blood was collected before and after exercise, at 2 and 7 hour postexercise, and before and every 30 minutes during the OGTT and was analyzed for IL-6, glucose and insulin. Postexercise IL-6 was greater in RES (8.01 ± 2.08 pg · mL(-1)) vs. in AER (4.26 ± 0.27 pg · mL(-1)), and both were greater than in CON (1.61 ± 0.18 pg · mL(-1)). During the OGTT, there were no differences in glucose or insulin between conditions for single time points or as area under the curve. The RES caused greater IL-6 levels immediately after exercise that may be related to the greater active muscle mass compared to AER. Neither exercise produced enhanced glucose removal compared to control; thus, despite the greater elevation in IL-6 in RES, for these exercise conditions and this population, this cytokine did not influence glucose tolerance.     

Salivary hormone and immune responses to three resistance exercise schemes in elite female athletes

This study examined the salivary hormone and immune responses of elite female athletes to 3 different resistance exercise schemes. Fourteen female basketball players each performed an endurance scheme (ES-4 sets of 12 reps, 60% of 1 repetition maximum (1RM) load, 1-minute rest periods), a strength-hypertrophy scheme (SHS-1 set of 5RM, 1 set of 4RM, 1 set of 3RM, 1 set of 2RM, and 1set of 1RM with 3-minute rest periods, followed by 3 sets of 10RM with 2-minute rest periods) and a power scheme (PS-3 sets of 10 reps, 50% 1RM load, 3-minute rest periods) using the same exercises (bench press, squat, and biceps curl). Saliva samples were collected at 07:30 hours, pre-exercise (Pre) at 09:30 hours, postexercise (Post), and at 17:30 hours. Matching samples were also taken on a nonexercising control day. The samples were analyzed for testosterone, cortisol (C), and immunoglobulin A concentrations. The total volume of load lifted differed among the 3 schemes (SHS > ES > PS, p < 0.05). Postexercise C concentrations increased after all schemes, compared to control values (p < 0.05). In the SHS, the postexercise C response was also greater than pre-exercise data (p < 0.05). The current findings confirm that high-volume resistance exercise schemes can stimulate greater C secretion because of higher metabolic demand. In terms of practical applications, acute changes in C may be used to evaluate the metabolic demands of different resistance exercise schemes, or as a tool for monitoring training strain.     

Increased number of forced repetitions does not enhance strength development with resistance training

Some research suggests that strength improvements are greater when resistance training continues to the point at which the individual cannot perform additional repetitions (i.e., repetition failure). Performing additional forced repetitions after the point of repetition failure and thus further increasing the set volume is a common resistance training practice. However, whether short-term use of this practice increases the magnitude of strength development with resistance training is unknown and was investigated here. Twelve basketball and 10 volleyball players trained 3 sessions per week for 6 weeks, completing either 4 x 6, 8 x 3, or 12 x 3 (sets x repetitions) of bench press per training session. Compared with the 8 x 3 group, the 4 x 6 protocol involved a longer work interval and the 12 x 3 protocol involved higher training volume, so each group was purposefully designed to elicit a different number of forced repetitions per training session. Subjects were tested on 3- and 6-repetition maximum (RM) bench press (81.5 +/- 9.8 and 75.9 +/- 9.0 kg, respectively, mean +/- SD), and 40-kg Smith Machine bench press throw power (589 +/- 100 W). The 4 x 6 and 12 x 3 groups had more forced repetitions per session (p < 0.01) than did the 8 x 3 group (4.1 +/- 2.6, 3.1 +/- 3.5, and 1.2 +/- 1.8 repetitions, respectively), whereas the 12 x 3 group performed approximately 40% greater work and had 30% greater concentric time. As expected, all groups improved 3RM (4.5 kg, 95% confidence limits, 3.1- 6.0), 6RM (4.7 kg, 3.1-6.3), bench press throw peak power (57 W, 22-92), and mean power (23 W, 4-42) (all p < or = 0.02). There were no significant differences in strength or power gains between groups. In conclusion, when repetition failure was reached, neither additional forced repetitions nor additional set volume further improved the magnitude of strength gains. This finding questions the efficacy of adding additional volume by use of forced repetitions in young athletes with moderate strength training experience.     

Rest-interval length affects leukocyte levels during heavy resistance exercise

We sought to determine the effect of varying rest intervals on leukocyte levels during heavy resistance exercise. Nine college men completed 2 exercise bouts of 10 sets of 10 repetitions at 65% 1 repetition maximum (1RM) leg press with 1- (1MIN) or 3-minute (3MIN) rest intervals, respectively. Blood collected at rest (PRE), immediately postexercise (POST), and 1.5 hours postexercise (1.5H) was analyzed for leukocyte levels. Data were analyzed using a 2 x 3 repeated measures analysis of variance. A greater PRE-POST lymphocytosis (+83% vs. +16%, p = 0.002) and monocytosis (+47% vs. +15%, p = 0.005) was observed following 1MIN vs. 3MIN. Serum creatine kinase (CK) activity was increased to a greater extent 24 h postexercise following the 1-minute rest protocol (p = 0.022). CK was correlated (r = 0.611) to the PRE-POST lymphocytosis. We conclude that short rest intervals increase the extent of postexercise lymphocytosis and monocytosis, when total work is kept constant.     

Time course of proteolytic, cytokine, and myostatin gene expression after acute exercise in human skeletal muscle.

The aim of this study was to examine the time course induction of select proteolytic [muscle ring finger-1 (MuRF-1), atrogin-1, forkhead box 3A (FOXO3A), calpain-1, calpain-2], myostatin, and cytokine (IL -6, -8, -15, and TNF-alpha) mRNA after an acute bout of resistance (RE) or run (RUN) exercise. Six experienced RE (25 +/- 4 yr, 74 +/- 14 kg, 1.71 +/- 0.11 m) and RUN (25 +/- 4 yr, 72 +/- 5 kg, 1.81 +/- 0.07 m) subjects had muscle biopsies from the vastus lateralis (RE) or gastrocnemius (RUN) before, immediately after, and 1, 2, 4, 8, 12, and 24 h postexercise. RE increased (P < 0.05) mRNA expression of MuRF-1 early (3.5-fold, 1-4 h), followed by a decrease in atrogin-1 (3.3-fold) and FOXO3A (1.7-fold) 8-12 h postexercise. Myostatin mRNA decreased (6.3-fold; P < 0.05) from 1 to 24 h postexercise, whereas IL-6, IL-8, and TNF-alpha mRNA were elevated 2-12 h. RUN increased (P < 0.05) MuRF-1 (3.6-fold), atrogin-1 (1.6-fold), and FOXO3A (1.9-fold) 1-4 h postexercise. Myostatin was suppressed (3.6-fold; P < 0.05) 8-12 h post-RUN. The cytokines exhibited a biphasic response, with immediate elevation (P < 0.05) of IL-6, IL-8, and TNF-alpha, followed by a second elevation (P < 0.05) 2-24 h postexercise. In general, the timing of the gene induction indicated early elevation of proteolytic genes, followed by prolonged elevation of cytokines and suppression of myostatin. These data provide basic information for the timing of human muscle biopsy samples for gene expression studies involving exercise. Furthermore, this information suggests a greater induction of proteolytic genes following RUN compared with RE.     

Effects of age on testosterone responses to resistance exercise and musculoskeletal variables in men

This study compared serum total testosterone (TT) and free testosterone (FT) responses of young (20-26 years, n = 8), middle-aged (38-53 years, n = 7), and older (59-72 years, n = 9) men to resistance exercise. We also examined the relationships between testosterone (T) levels and strength, bone mineral density (BMD), and body composition variables for each age group. Subjects were tested for isotonic muscular strength (1 repetition maximum [1RM]), BMD (dual-energy x-ray absorptiometry [DXA]) and body composition (DXA). Each group performed an acute exercise protocol (3 sets, 10 repetitions, 80% of 1RM, 6 exercises). Blood samples were obtained at baseline, immediately postexercise, and 15 minutes postexercise for the TT and FT assays. The older age group had significantly (p < 0.05) lower T levels than the young group, but each group exhibited an increase (p < 0.05) in TT and FT immediately postexercise. Total T and FT were significantly correlated (p < 0.05) with strength in middle-aged and older men and with bone-free lean tissue mass in older men. In conclusion, middle-aged and older men showed similar relative T responses to those of younger men to a single bout of high-intensity resistance exercise. However, T levels were related to strength and muscle mass only in middle-aged or older men. On a practical application level, older men can complete a high-intensity resistance exercise program resulting in spikes in T that may attenuate age-related muscle and BMD loss.     

Short vs. long rest period between the sets in hypertrophic resistance training: influence on muscle strength, size, and hormonal adaptations in trained men

Acute and long-term hormonal and neuromuscular adaptations to hypertrophic strength training were studied in 13 recreationally strength-trained men. The experimental design comprised a 6-month hypertrophic strength-training period including 2 separate 3-month training periods with the crossover design, a training protocol of short rest (SR, 2 minutes) as compared with long rest (LR, 5 minutes) between the sets. Basal hormonal concentrations of serum total testosterone (T), free testosterone (FT), and cortisol (C), maximal isometric strength of the leg extensors, right leg 1 repetition maximum (1RM), dietary analysis, and muscle cross-sectional area (CSA) of the quadriceps femoris by magnetic resonance imaging (MRI) were measured at months 0, 3, and 6. The 2 hypertrophic training protocols used in training for the leg extensors (leg presses and squats with 10RM sets) were also examined in the laboratory conditions at months 0, 3, and 6. The exercise protocols were similar with regard to the total volume of work (loads x sets x reps), but differed with regard to the intensity and the length of rest between the sets (higher intensity and longer rest of 5 minutes vs. somewhat lower intensity but shorter rest of 2 minutes). Before and immediately after the protocols, maximal isometric force and electromyographic (EMG) activity of the leg extensors were measured and blood samples were drawn for determination of serum T, FT, C, and growth hormone (GH) concentrations and blood lactate. Both protocols before the experimental training period (month 0) led to large acute increases (p < 0.05-0.001) in serum T, FT, C , and GH concentrations, as well as to large acute decreases (p < 0.05-0.001) in maximal isometric force and EMG activity. However, no significant differences were observed between the protocols. Significant increases of 7% in maximal isometric force, 16% in the right leg 1RM, and 4% in the muscle CSA of the quadriceps femoris were observed during the 6-month strength-training period. However, both 3-month training periods performed with either the longer or the shorter rest periods between the sets resulted in similar gains in muscle mass and strength. No statistically significant changes were observed in basal hormone concentrations or in the profiles of acute hormonal responses during the entire 6-month experimental training period. The present study indicated that, within typical hypertrophic strength-training protocols used in the present study, the length of the recovery times between the sets (2 vs. 5 minutes) did not have an influence on the magnitude of acute hormonal and neuromuscular responses or long-term training adaptations in muscle strength and mass in previously strength-trained men.     

Occurrence of fatigue during sets of static squat jumps performed at a variety of loads

Research has identified that the optimal power load for static squat jumps (with no countermovement) is lower than the loads usually recommended for power training. Lower loads may permit the performance of additional repetitions before the onset of fatigue compared with heavier loads; therefore, the aim of this study was to determine the point of fatigue during squat jumps at various loads (0, 20, 40, 60% 1-repetition maximum [1RM]). Seventeen professional rugby league players performed sets of 6 squat jumps (with no countermovement), using 4 loading conditions (0, 20, 40, and 60% of 1RM back squat). Repeated measures analysis of variance revealed no significant differences (p > 0.05) in force, velocity, power, and displacement between repetitions, for the 0, 20, and 40% loading conditions. The 60% condition showed no significant difference (p > 0.05) in peak force between repetitions; however, velocity (1.12 + 0.10 and 1.18 + 0.11 m·s(-1)), power (3,385 + 343 and 3,617 + 396 W) and displacement (11.13 + 2.31 and 11.85 + 2.16 cm) were significantly (p < 0.02) lower during repetition 6 compared with repetition 2. These findings indicate that when performing squat jumps (with no countermovement) with a load <40% 1RM back squat, up to >6 repetitions can be completed without inducing fatigue and a minimum of 4-6 repetitions should be performed to achieve peak power output. When performing squat jumps (with no countermovement) with a load equal to the 60% 1RM only, 5 repetitions should be performed to minimize fatigue and ensure maintenance of velocity and power.     

Time course of myogenic and metabolic gene expression in response to acute exercise in human skeletal muscle.

The aim of this study was to examine the time course activation of select myogenic (MRF4, Myf5, MyoD, myogenin) and metabolic (CD36, CPT1, HKII, and PDK4) genes after an acute bout of resistance (RE) or run (Run) exercise. Six RE subjects [25 +/- 4 yr (mean +/- SD), 74 +/- 14 kg, 1.71 +/- 0.11 m] and six Run subjects (25 +/- 4 yr, 72 +/- 5 kg, 1.81 +/- 0.07 m, 63 +/- 8 ml.kg(-1).min(-1)) were studied. Eight muscle biopsies were taken from the vastus lateralis (RE) and gastrocnemius (Run) before, immediately after, and 1, 2, 4, 8, 12 and 24 h after exercise. RE increased mRNA of MRF4 (3.7- to 4.5-fold 2-4 h post), MyoD (5.8-fold 8 h post), myogenin (2.6- and 3.5-fold 8-12 h post), HKII (3.6- to 10.5-fold 2-12 h post), and PDK4 (14- to 26-fold 2-8 h post). There were no differences in Myf5, CD36, and CPT1 mRNA levels 0-24 h post-RE. Run increased mRNA of MyoD (5.0- to 8.0-fold), HKII (12- to 16-fold), and PDK4 (32- to 52-fold) at 8-12 h postexercise. There were no differences in MRF4, Myf5, myogenin, CD36 and CPT1 mRNA levels 0-24 h post-Run. These data indicate a myogenic and metabolic gene induction with RE and Run exercise. The timing of the gene induction is variable and generally peaks 4-8 h postexercise with all gene expression not significantly different from the preexercise levels by 24 h postexercise. These data provide basic information for the timing of human muscle biopsy samples for gene-expression studies involving exercise.