Hormonal responses and adaptations to resistance exercise and training

Exercise improves glucose homeostasis that has been impaired by a high-fat diet by potentiating pancreatic β-cell function and mass through IRS2 in diabetic rats

In this study, we investigated the effects of a high-fat diet and exercise on pancreatic β-cell function and mass and its molecular mechanism in 90% pancreatectomized male rats. The pancreatectomized diabetic rats were given control diets (20% energy) or a high-fat (HF) diet (45% energy) for 12 wk. Half of each group was given regular exercise on an uphill treadmill at 20 m/min for 30 min 5 days/wk. HF diet lowered first-phase insulin secretion with glucose loading, whereas exercise training reversed this decrease. However, second-phase insulin secretion did not differ among the groups. Exercise increased pancreatic β-cell mass. This resulted from stimulated β-cell proliferation and reduced apoptosis, which is associated with potentiated insulin or IGF-I signaling through insulin receptor substrate-2 (IRS2) induction. Although the HF diet resulted in decreased proliferation and accelerated apoptosis by weakened insulin and IGF-I signaling from reduction of IRS2 protein, β-cell mass was maintained in HF rats just as much as in control rats via increased individual β-cell size and neogenesis from precursor cells. Consistent with the results of β-cell proliferation, pancreas duodenal homeobox-1 expression increased in the islets of rats in the exercise groups, and it was reduced the most in rats fed the HF diet. In conclusion, exercise combined with a moderate fat diet is a good way to maximize β-cell function and mass through IRS2 induction to alleviate the diabetic condition. This study suggests that dietary fat contents and exercise modulate β-cell function and mass to overcome insulin resistance in two different pathways.

Neuromuscular and hormonal responses to a single session of whole body vibration exercise in healthy young men

Whole body vibration (WBV) has been proposed as an alternative exercise stimulus to produce adaptive responses similar to resistance exercise. Few studies have analysed acute hormonal responses to WBV. Purpose To evaluate neuromuscular and hormonal responses to an acute bout of isometric half-squat exercise with and without superimposition of WBV. Methods Seven healthy males (22.3+/-2.7 years) performed 10 sets of half squat isometric exercise for 1 min with 1-min rest between sets. Two separate trials were conducted either with WBV [30 Hz; 3.5 g (1 g=9.81 m.s2)] or without vibration (Control). Salivary concentration of testosterone and cortisol was collected and maximal isometric unilateral knee extensions (MVC) were completed before, immediately after, 1, 2 and 24 h after treatment. Results Significant decreases in MVC were observed immediately after (229.4+/-53.2 Nm), 1 h (231.6+/-59.9 Nm), and 2 h (233.0+/-59.1 Nm) after WBV compared with baseline (252.7+/-56.4 Nm; P<0.05). No significant change in MVC was recorded in Control. Rate of torque development in the first 200 ms (RTD200 ms), and salivary testosterone and cortisol concentrations were unaffected in both conditions. However, there was a trend for change over time in cortisol (P=0.052), with an increase after WBV and decrease after Control. Conclusion A 10 min session of intermittent WBV was shown to produce an acute reduction in MVC in healthy individuals, which recovered after 24 h. No significant changes were identified in salivary concentration of testosterone and cortisol suggesting that WBV with low acceleration does not represent a stressful stimulus for the neuroendocrine system.

Alterations in IGF-I affect elderly: role of physical activity

The growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. However, it is clear that overexpression of IGF-I in the muscle can protect against age-related sarcopenia. Strength training appears to be the intervention of choice for the prevention and treatment of sarcopenia. IGF-I has been implicated in the loss of the muscle with age, and IGF-I expression levels change as a consequence of strength training in older adults. However, it seems that advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition in women and men. We concluded that resistive exercise is a significant determinant of muscle mass and function. Elevated levels of IGF-I have been found in physically active compared to sedentary individuals. Recent work suggests that IGF-I as a mediator plays an important role in muscle hypertrophy and angiogenesis, both of which characterize the anabolic adaptation of muscles to exercise.

Neuroendocrine responses to an acute bout of eccentric-enhanced resistance exercise

PURPOSE

The purpose of this study was to compare the total testosterone (TT), bioavailable testosterone (BT), growth hormone (GH), lactate, and ratings of perceived exertion (RPE) responses between a single bout of traditional (TRAD) and eccentric-enhanced resistance exercise (ECC+) of matched training volumes.

METHODS

Twenty-two previously untrained males (21.9+/-0.8 yr) completed one familiarization and one baseline 1RM testing bout, for the bench press and squat exercises, and then two exercise bouts. During exercise bout 1, all subjects completed a TRAD protocol (four sets of six reps at 52.5% 1RM), and the subsequent exercise bout consisted of either a TRAD or an ECC+ protocol (three sets of six reps at 40% 1RM concentric and 100% 1RM eccentric) for the bench press and squat exercises. Blood samples acquired at rest, immediately after (T1), and 15, 30, 45, and 60 min after exercise were assessed for serum TT, BT, GH, and blood lactate concentrations.

RESULTS

Resting and postexercise TT, BT, and GH were not significantly different between groups. Postexercise TT was not elevated during either bout or in either group, whereas BT increased 15-16% at T1 in both groups during bout 2. Postexercise GH concentrations were elevated 500-7000% above baseline after both protocols. Postexercise lactate accumulation and RPE were greater with ECC+ than TRAD.

CONCLUSION

TRAD and ECC+ show similar neuroendocrine and differing metabolic responses during the early phase of resistance exercise in untrained, college-age men.

Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis

Low-intensity resistance exercise training combined with blood flow restriction (REFR) increases muscle size and strength as much as conventional resistance exercise with high loads. However, the cellular mechanism(s) underlying the hypertrophy and strength gains induced by REFR are unknown. We have recently shown that both the mammalian target of rapamycin (mTOR) signaling pathway and muscle protein synthesis (MPS) were stimulated after an acute bout of high-intensity resistance exercise in humans. Therefore, we hypothesized that an acute bout of REFR would enhance mTOR signaling and stimulate MPS. We measured MPS and phosphorylation status of mTOR-associated signaling proteins in six young male subjects. Subjects were studied once during blood flow restriction (REFR, bilateral leg extension exercise at 20% of 1 repetition maximum while a pressure cuff was placed on the proximal end of both thighs and inflated at 200 mmHg) and a second time using the same exercise protocol but without the pressure cuff [control (Ctrl)]. MPS in the vastus lateralis muscle was measured by using stable isotope techniques, and the phosphorylation status of signaling proteins was determined by immunoblotting. Blood lactate, cortisol, and growth hormone were higher following REFR compared with Ctrl (P < 0.05). Ribosomal S6 kinase 1 (S6K1) phosphorylation, a downstream target of mTOR, increased concurrently with a decreased eukaryotic translation elongation factor 2 (eEF2) phosphorylation and a 46% increase in MPS following REFR (P < 0.05). MPS and S6K1 phosphorylation were unchanged in the Ctrl group postexercise. We conclude that the activation of the mTOR signaling pathway appears to be an important cellular mechanism that may help explain the enhanced muscle protein synthesis during REFR.

Increase in kinins on post-exercise hypotension in normotensive and hypertensive volunteers

Post-exercise hypotension is an important event for blood pressure regulation, especially in hypertensive individuals. Although post-exercise hypotension is a well-known phenomenon, the mechanism responsible is still unclear. The kallikrein-kinin system is involved in blood pressure control, but its role in post-exercise hypotension has not yet been investigated. Thus, the purpose of this study was to investigate the involvement of the vasodilators bradykinin and des-Arg(9)-BK and kallikrein activity in post-exercise hypotension promoted by 35 min of cycle ergometer (CE) or circuit weight-training (CWT) bouts in normotensive and hypertensive individuals. A significant decrease in mean arterial pressure at 45 and 60 min after CE and 45 min after CWT was observed in normotensive individuals. Hypertensive values of mean arterial pressure were significantly reduced at 45 and 60 min after CE and at 60 min after CWT. Before exercise, plasma bradykinin concentrations and kallikrein activity were higher in hypertensive compared to normotensive volunteers. Kinin levels increased in the groups evaluated at the end of the training period and 60 min post-exercise. These data suggest that the kallikrein-kinin system may be involved in post-exercise hypotension in normotensive and hypertensive individuals subjected to CE and CWT bouts.

The influence of frequency, intensity, volume and mode of strength training on whole muscle cross-sectional area in humans

Strength training is an important component in sports training and rehabilitation. Quantification of the dose-response relationships between training variables and the outcome is fundamental for the proper prescription of resistance training. The purpose of this comprehensive review was to identify dose-response relationships for the development of muscle hypertrophy by calculating the magnitudes and rates of increases in muscle cross-sectional area induced by varying levels of frequency, intensity and volume, as well as by different modes of strength training. Computer searches in the databases MEDLINE, SportDiscus and CINAHL were performed as well as hand searches of relevant journals, books and reference lists. The analysis was limited to the quadriceps femoris and the elbow flexors, since these were the only muscle groups that allowed for evaluations of dose-response trends. The modes of strength training were classified as dynamic external resistance (including free weights and weight machines), accommodating resistance (e.g. isokinetic and semi-isokinetic devices) and isometric resistance. The subcategories related to the types of muscle actions used. The results demonstrate that given sufficient frequency, intensity and volume of work, all three types of muscle actions can induce significant hypertrophy at an impressive rate and that, at present, there is insufficient evidence for the superiority of any mode and/or type of muscle action over other modes and types of training. Tentative dose-response relationships for each variable are outlined, based on the available evidence, and interactions between variables are discussed. In addition, recommendations for training and suggestions for further research are given.

Plasma agouti-related protein (AGRP), growth hormone, insulin responses to a single circuit-resistance exercise in male college students

The ability of acute exercise to stimulate appetite and food intake depends on intensity, duration, and agouti-related protein (AGRP) levels. Fasting, as well as any negative energy balance, has been reported to increase AGRP expression in the arcuate nucleus (ARC) of the hypothalamus and other extra-hypothalamic tissues in human and rats. The purpose of the present study was to investigate the response of plasma AGRP, GH and insulin to a single circuit-resistance exercise. Twenty volunteer male college students completed a single bout of circuit-resistance training (10 exercises at 35% of 1RM). Blood samples were collected before, immediately and 30 min following the exercise protocol. Plasma AGRP and GH levels showed a significant increase immediately after exercise and returned to pre exercise values during the recovery period. The data indicate that exercise protocol was able to increase plasma AGRP and GH levels. A higher plasma AGRP level might result in an acute exercise-induced hyperphagia and help to fuel post-exercise restoration processes.

Influence of training on plasma adrenaline and noradrenaline kinetics in untrained standardbreds

REASONS FOR PERFORMING STUDY

Catecholamines (CAT) play an important role in modulating the response to exercise. But the kinetics of CAT changes during exercise are difficult to study due to their short biological half-life.

OBJECTIVES

Learning about variations in plasma CAT levels during training could furnish new information regarding sweating, redistribution of blood flow and energy metabolism.

METHODS

Four untrained Standardbreds, adapted to treadmill work, were used to determine the influence of training on plasma adrenaline (A) and noradrenaline (NA) kinetics. Horses underwent a standardised exercise test (SET) on treadmill before (SET1), and 1 (SET2) and 2 months after (SET3) the start of a moderate training period on treadmill. The SET procedure was: warm-up and a single step of 2 min at 200 beats/min heart rate (SS). The automatic blood collection system (that has been carried out during SS) and the preparation of the horses have been described previously. The system was programmed to obtain a blood sample every 15 sec (8 blood samples per SS). Analyses were performed by HPLC. Training progress was monitored by means of anaerobic threshold velocity (V4) and the velocity during SS (V200). Wilcoxon's test was used for statistical analysis.

RESULTS

Decreased levels of A and NA with significant differences between SET1/SET2 and SET1/SET3 for A (P = 0.007) and NA (P = 0.007) were found. There were no differences between SET2 and SET3 for A (P = 0.195) and NA (P = 0.054).

CONCLUSIONS

Training appears to influence the level of plasma CAT and this influence is greater during the first training period in untrained Standardbreds.

POTENTIAL RELEVANCE

It may prove interesting to associate the study of training-induced modifications of the concentration of plasma CAT with thermoregulation, which is under catecholaminergic control and undergoes important adaptations during training.

Short-term strength training and the expression of myostatin and IGF-I isoforms in rat muscle and tendon: differential effects of specific contraction types

In skeletal muscle, an increased expression of insulin like growth factor-I isoforms IGF-IEa and mechano-growth factor (MGF) combined with downregulation of myostatin is thought to be essential for training-induced hypertrophy. However, the specific effects of different contraction types on regulation of these factors in muscle are still unclear, and in tendon the functions of myostatin, IGF-IEa, and MGF in relation to training are unknown. Female Sprague-Dawley rats were subjected to 4 days of concentric, eccentric, or isometric training ( n = 7–9 per group) of the medial gastrocnemius, by stimulation of the sciatic nerve during general anesthesia. mRNA levels for myostatin, IGF-IEa, and MGF in muscle and Achilles' tendon were measured by real-time RT-PCR. Muscle myostatin mRNA decreased in response to all types of training (2- to 8-fold) ( P < 0.05), but the effect of eccentric training was greater than concentric and isometric training ( P < 0.05). In tendon, myostatin mRNA was detected, but no changes were seen after exercise. IGF-IEa and MGF increased in muscle (up to 15-fold) and tendon (up to 4-fold) in response to training ( P < 0.01). In tendon no difference was seen between training types, but in muscle the effect of eccentric training was greater than concentric training for both IGF-IEa and MGF ( P < 0.05), and for IGF-IEa isometric training had greater effect than concentric ( P < 0.05). The results indicate a possible role for IGF-IEa and MGF in adaptation of tendon to training, and the combined changes in myostatin and IGF-IEa/MGF expression could explain the important effect of eccentric actions for muscle hypertrophy.

Efficacy and Feasibility of a Novel Tri-Modal Robust Exercise Prescription in a Retirement Community: A Randomized, Controlled Trial

OBJECTIVES

To test the feasibility and efficacy of current guidelines for multimodal exercise programs in older adults.

DESIGN

Randomized, controlled trial.

SETTING

Retirement village.

PARTICIPANTS

Thirty-eight subjects (14 men and 24 women) aged 76.6 +/- 6.1.

INTERVENTION

A wait list control or 10 weeks of supervised exercise consisting of high-intensity (80% of one-repetition maximum (1RM)) progressive resistance training (PRT) 3 days per week, moderate-intensity (rating of perceived exertion 11 to 14/20) aerobic training 2 days per week, and progressive balance training 1 day per week.

MEASUREMENTS

Blinded assessments of dynamic muscle strength (1RM), balance, 6-minute walk, gait velocity, chair stand, stair climb, depressive symptoms, self-efficacy, and habitual physical activity level.

RESULTS

Higher baseline strength and psychological well-being were associated with better functional performance. Strength gains over 10 weeks averaged 39+/-31% in exercise, versus 21+/-24% in controls (P=.10), with greater improvements in hip flexion (P=.01), hip abduction (P=.02), and chest press (P=.04) in the exercise group. Strength adaptations were greatest in exercises in which the intended continuous progressive overload was achieved. Stair climb power (12.3+/-15%, P=.002) and chair stand time (-7.1+/-15%, P=.006) improved significantly and similarly in both groups. Reduction in depressive symptoms was significantly related to compliance (attendance rate r=-0.568, P=.009, PRT progression in loading r=-0.587, P=.02, and total volume of aerobic training r=-0.541, P=.01), as well as improvements in muscle strength (r=-0.498, P=.002).

CONCLUSION

Robust physical and psychological adaptations to exercise are linked, although volumes and intensities of multiple exercise modalities sufficient to cause significant adaptation appear difficult to prescribe and adhere to simultaneously in older adults.

Suppression of endogenous testosterone production attenuates the response to strength training: a randomized, placebo-controlled, and blinded intervention study

We hypothesized that suppression of endogenous testosterone would inhibit the adaptations to strength training in otherwise healthy men. Twenty-two young men with minor experience with strength training participated in this randomized, placebo-controlled, double-blinded intervention study. The subjects were randomized to treatment with the GnRH analog goserelin (3.6 mg) or placebo (saline) subcutaneously every 4 wk for 12 wk. The strength training period of 8 wk, starting at week 4, included exercises for all major muscles [3-4 sets per exercise x 6-10 repetitions with corresponding 6- to 10-repetition maximum (RM) loads, 3/wk]. A strength test, blood sampling, and whole body DEXA scan were performed at weeks 4 and 12. Endogenous testosterone decreased significantly (P < 0.01) in the goserelin group from 22.6 +/- 5.5 (mean +/- SD) nmol/l to 2.0 +/- 0.5 (week 4) and 1.1 +/- 0.6 nmol/l (week 12), whereas it remained constant in the placebo group. The goserelin group showed no changes in isometric knee extension strength after training, whereas the placebo group increased from 240.2 +/- 41.3 to 264.1 +/- 35.3 Nm (P < 0.05 within and P = 0.05 between groups). Lean mass of the legs increased 0.37 +/- 0.13 and 0.57 +/- 0.30 kg in the goserelin and placebo groups, respectively (P < 0.05 within and P = 0.05 between groups). Body fat mass increased 1.4 +/- 1.0 kg and decreased 0.6 +/- 1.2 kg in the goserelin and placebo groups, respectively (P < 0.05 within and between groups). We conclude that endogenous testosterone is of paramount importance to the adaptation to strength training.

Suppression of testosterone does not blunt mRNA expression of myoD, myogenin, IGF, myostatin or androgen receptor post strength training in humans

We hypothesized that suppression of endogenous testosterone blunts mRNA expression post strength training (ST). Twenty-two young men were randomized for treatment with the GnRH analogue goserelin (3.6 mg every 4 weeks) or placebo for a period of 12 weeks. The ST period of 8 weeks started at week 4. Strength test, blood sampling, muscle biopsies, and whole-body dual-energy X-ray absorptiometry (DXA) scan were performed at weeks 4 and 12. Muscle biopsies were taken during the final ST session (pre, post 4 h, and post 24 h). Resting serum testosterone decreased significantly (P < 0.01) in the goserelin group from 22.6 +/- 1.6 (mean +/- s.e.m.) to 2.0 +/- 0.1 nmol l(-1) (week 4), whereas it remained unchanged in the placebo group. An acute increase of serum testosterone was observed during the final ST session in the placebo group (P < 0.05), whereas a decreased response was observed in the goserelin group (P < 0.05). mRNA expression of IGF-IE(bc) and myogenin increased, while expression of myostatin decreased (P < 0.01); however, no differences were observed between the groups. Muscle strength and muscle mass showed a tendency to increase more in the placebo group than in the goserelin group (P = 0.05). In conclusion, despite blocked acute responses of testosterone and 10- to 20-fold lower resting levels in the goserelin group, ST resulted in a similar mRNA expression of myoD, myogenin, IGF-IE(abc), myostatin and androgen receptor as observed in the placebo group. Therefore, in the present study, the molecular events were the same, despite divergent muscle hypertrophy and strength gains.

The acute effects of different whole body vibration amplitudes on the endocrine system of young healthy men: a preliminary study

Whole body vibration (WBV) has been suggested as an alternative form of exercise producing adaptive responses similar to that of resistance training. Very limited information is available on the effects of different vibration parameters on anabolic hormones. In this study, we compared the acute effects of different WBV amplitudes on serum testosterone (T) and insulin growth factor-1 (IGF-1). Nine healthy young recreationally active adult males (age 22 +/- 2 years, height 181 +/- 6.3 cm, weight 77.4 +/- 9.5 kg) voluntarily participated in this randomized controlled (cross-over design) study. The subjects performed 20 sets of 1 min each of WBV exercise in the following conditions: Non-vibration condition (control), low amplitude vibration [low (30 Hz, 1.5 mm peak-to-peak amplitude)] and high amplitude vibration [high (30 Hz, 3 mm peak-to-peak amplitude)]. Blood samples were collected before, after 10 sets, at the end (20th set) and after 24 h of the exercise bout. WBV exercise did not produce significant changes in serum T and IGF-1 either with low or high amplitude when compared with the control condition. The results of this study demonstrate that a single session of WBV exposure with a frequency of 30 Hz and amplitudes of 1.5 and 3 mm does not noticeably alter serum T and IGF-1 levels.

Contralateral effects of unilateral strength training: evidence and possible mechanisms

If exercises are performed to increase muscle strength on one side of the body, voluntary strength can increase on the contralateral side. This effect, termed the contralateral strength training effect, is usually measured in homologous muscles. Although known for over a century, most studies have not been designed well enough to show a definitive transfer of strength that could not be explained by factors such as familiarity with the testing. However, an updated meta-analysis of 16 properly controlled studies (range 15–48 training sessions) shows that the size of the contralateral strength training effect is ∼8% of initial strength or about half the increase in strength of the trained side. This estimate is similar to results of a large, randomized controlled study of training for the elbow flexors (contralateral effect of 7% initial strength or one-quarter of the effect on the trained side). This is likely to reflect increased motoneuron output rather than muscular adaptations, although most methods are insufficiently sensitive to detect small muscle contributions. Two classes of central mechanism are identified. One involves a “spillover” to the control system for the contralateral limb, and the other involves adaptations in the control system for the trained limb that can be accessed by the untrained limb. Cortical, subcortical and spinal levels are all likely to be involved in the “transfer,” and none can be excluded with current data. Although the size of the effect is small and may not be clinically significant, study of the phenomenon provides insight into neural mechanisms associated with exercise and training.

Hyperinsulinaemia, hyperaminoacidaemia and post-exercise muscle anabolism: the search for the optimal recovery drink

Dietary supplements and other ergogenic aids are popular among athletes. Recent studies have shown that nutritional mixtures containing protein hydrolysates, added leucine, and high-glycaemic carbohydrates greatly augment insulin secretion compared with high-glycaemic carbohydrates only. When post-exercise hyperinsulinaemia is supported by hyperaminoacidaemia induced by protein hydrolysate and leucine ingestion, net protein deposition in muscle should occur. Thus, consumption of post-exercise recovery drinks containing these nutrients in conjunction with appropriate resistance training may lead to increased skeletal muscle hypertrophy and strength. However, the long-term effects on body composition and exercise performance remain to be determined.

Acute BDNF and cortisol response to low intensity exercise and following ramp incremental exercise to exhaustion in humans

The effect of short-term aerobic exercise and a following ramp incremental cycle ergometry to exhaustion on the acute response of the serum concentrations of brain derived neurotrophic factor (BDNF) and cortisol (COR) was examined in 8 healthy male athletes. Venous and capillary blood samples were drawn at rest, immediately after a 10 min warm-up period with aerobic exercise and after a ramp test to exhaustion, as well as 3, 6, 10 and 15 min post exercise. Capillary blood lactate (LA) concentration and blood gases as well as serum BDNF and COR concentrations did not change during the warm-up period. LA was increased (p<0.05) at the end of the ramp test and during recovery period while bicarbonate concentration, carbon dioxide pressure, pH and base excess were decreased (p<0.05) during this period. Serum BDNF was increased at the point of exhaustion (p<0.05) while no significant differences were found between values at rest and those during recovery period. At 10 and 15 min post incremental exercise, COR concentrations were increased (p<0.05) compared to rest. The present study is the first to demonstrate in humans that in contrast to short duration aerobic exercise immediately after a following short duration high-intensity exercise to exhaustion, there is a transient augmentation of serum BDNF concentration. Short-term response of serum BDNF and COR concentrations differs as BDNF returns to baseline level faster than COR.

Ghrelin and glucoregulatory hormone responses to a single circuit resistance exercise in male college students

INTRODUCTION

It has been suggested that ghrelin may play a role in growth hormone (GH) secretion to exercise.

OBJECTIVE

The present study was designed to examine the effects of a single bout of circuit resistance exercise on plasma glucose, ghrelin, GH, and c-peptide, and cortisol.

DESIGN AND METHODS

Fourteen volunteer male physical education students completed a single bout circuit resistance training (10 exercises, three circuits, and at 60% of 1-RM). Blood samples were collected before, immediately after the exercise, and 24-h following the exercise protocol.

RESULTS

GH, glucose, and c-peptide showed a significant increase immediately after exercise and returned to pre exercise values over time. Plasma ghrelin showed a significant decrease immediately after the exercise and increased significantly 24-h following the exercise.

CONCLUSION

In conclusion, a decrease in plasma ghrelin following a single bout of circuit resistance exercise indicates that an increase in GH is not related to plasma ghrelin levels. An acute exercise-induced hyperphagia during the long-recovery was considered.

Effects of Unaccustomed and Accustomed Exercise on the Immune Response in Runners

PURPOSE

To test the hypothesis that long-term immunological response may be different after accustomed concentric and unaccustomed eccentric exercise in endurance-trained men.

METHODS

Fourteen highly endurance-trained male runners performed two bouts of high-intensity exercise with at least 2-wk intervals between bouts. Concentric exercise consisted of a 60-min level run with a targeted heart rate of 80% VO2 peak. Eccentric exercise was conducted lying on a specially designed exercise rack, eliciting eccentric action of the musculus quadriceps femoris. Blood samples were taken before and 1, 6, 24, 72, and 144 h after exercise to determine creatine kinase (CK), C-reactive protein (CRP), and interleukin-6 (IL-6). Lymphocyte subset distribution was assessed using flow cytometry.

RESULTS

We found a significant (P < 0.05) increase of CD4 (eccentric: 17%; concentric: 20%), CD3+/CD4+ (16 vs 19%), CD25+ (45 vs 29%), CD25+/CD4+ (27 vs 50%), HLA-DR+ (20 vs 15%), HLA-DR+/CD4+ (16 vs 67%), and CD19+/CD45+ (52 vs 103%) positive lymphocytes 1 h after both exercise bouts. However, eccentric exercise resulted in a significantly higher and longer (6 h) increase of CD25+/CD4+ and HLA-DR+/CD8+ lymphocytes and a peak increase of CK at 72 h. IL-6 and CRP increased only after concentric exercise within the first 24 h. Both exercises resulted in a decrease of monocyte activation (LFA-1: CD18+/CD11a+) after 6 h, with an increase for the eccentric exercise part after 24 h (P < 0.05).

CONCLUSION

Accustomed concentric exercise mainly induced an acute-phase response, with increased CRP, IL-6, and activation of CD4 lymphocyte subsets. Unaccustomed eccentric exercise provided a delayed increase in CK and activation of monocytes and CD4+ and CD8+ subsets. Therefore, the immunological reaction depends not only on the type of contraction but also on the adaptation to the exercise.

Hypertrophy with unilateral resistance exercise occurs without increases in endogenous anabolic hormone concentration

We aimed to gain insight into the role that the transitory increases in anabolic hormones play in muscle hypertrophy with unilateral resistance training. Ten healthy young male subjects (21.8 +/- 0.4 years, 1.78 +/- 0.04 m, 75.6 +/- 2.9 kg; mean +/- SE) engaged in unilateral resistance training for 8 week (3 days/week). Exercises were knee extension and leg press performed at 80-90% of the subject's single repetition maximum (1RM). Blood samples were collected in the acute period before and after the first training bout and following the last training bout and analyzed for total testosterone, free-testosterone, luteinizing hormone, sex hormone binding globulin, growth hormone, cortisol, and insulin-like growth factor-1. Thigh muscle cross sectional area (CSA) and muscle fibre CSA by biopsy (vastus lateralis) were measured pre- and post-training. Acutely, no changes in systemic hormone concentrations were observed in the 90 min period following exercise and there was no influence of training on these results. Training-induced increases were observed in type IIx and IIa muscle fibre CSA of 22 +/- 3 and 13 +/- 2% (both P < 0.001). No changes were observed in fibre CSA in the untrained leg (all P > 0.5). Whole muscle CSA increased by 5.4 +/- 0.9% in the trained leg (P < 0.001) and remained unchanged in the untrained leg (P = 0.76). Isotonic 1RM increased in the trained leg for leg press and for knee extension (P < 0.001). No changes were seen in the untrained leg. In conclusion, unilateral training induced local muscle hypertrophy only in the exercised limb, which occurred in the absence of changes in systemic hormones that ostensibly play a role in muscle hypertrophy.

Effects of resistance exercise session after oral ingestion of melatonin on physiological and performance responses of adult men

This study investigated the effects of a heavy resistance exercise session (RES) with the oral daytime ingestion of melatonin on the physiological responses and acute performance. In a randomized and double-blind controlled study 10 healthy male subjects undertook an 80 min intensive hypertrophic RES for major muscles of the lower and upper extremities. The subjects were studied on two occasions receiving either melatonin (6 mg) or placebo (6 mg) in random order 60 min before each RES. Blood samples were taken from an antecubital vein both in fasting conditions in the morning and before RES (pre 60 min, pre 0 min), during RES (middle) and after RES (post 0 min, post 15 min, post 30 min, post 60 min). Maximal jumping ability and maximal strength in bench press and squat were measured before and immediately after RES in which there were no differences between the melatonin and placebo groups. The serum melatonin concentration increased significantly (P<0.05-0.001) in the melatonin group following oral ingestion of melatonin and was elevated at every time point after that. The concentration reached a peak value of 1171.3+/-235.2 pg/ml in 60 min at pre 0. Serum melatonin increased slightly but significantly (P<0.05) also in the placebo group just before RES, in the middle of RES and after RES (post 0, post 15). There were large differences (P<0.01-0.001) in the serum melatonin concentration between the groups at all time points. There were no differences in the growth hormone (GH), testosterone and cortisol peak concentrations at any time points between the groups but the area under the curve of GH during RES (P<0.01) and during the 60 min after RES (P<0.05) was lower in the melatonin condition. In conclusion, the present findings give evidence that oral ingestion of melatonin (6 mg) during daytime with heavy resistance exercise may slightly decrease GH concentrations. On the other hand, it seems that melatonin administration during daytime does not have any acute (1-2 h) effects either on the maximal jumping ability or on the maximal strength.

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 (Pmean), peak power (Ppeak) and velocity at Ppeak (Vppeak) 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 Pmean, 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, Pmean and Ppeak increased only in S, concomitantly with increased Vppeak 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.

Prior resistance training and sex influence muscle responses to arm suspension

PURPOSE

The magnitude of atrophy and strength loss induced by partial or complete disuse of skeletal muscles varies greatly among individuals. Factors predisposing some individuals to more extreme responses have not been identified. The purpose of this investigation was to determine whether 1) level of activity before disuse or 2) sex differences influence the magnitude of atrophy and changes in muscle strength, endurance, and sense of muscular effort in response to 21 d of arm suspension.

METHODS

Thirty-one individuals (18 women, 13 men) completed either 8 wk of resistance training (TRAINED group) or no training (UNTRAINED group) before 21 d of elbow muscle arm suspension achieved by having one arm in a sling tethered to the body by a swathe. Muscle volume was measured using serial magnetic resonance imaging (MRI) cross-sectional images. Functional measurements included maximal isometric force (MIF) for elbow flexion, one-repetition maximum (1RM) for biceps curl, number of repetitions to fatigue at 50% of 1RM, and sense of muscular effort measured using a force-matching task.

RESULTS

Flexor muscle volume decreased (P < 0.001) by -7.7 +/- 7.3% across all subjects. The decrease (P < 0.001) in flexor muscle volume was significant in men but not women. Arm suspension induced decreases (P < 0.001) in MIF and 1RM that did not differ across sex or training groups. The number of repetitions to fatigue decreased (P < 0.05) in the UNTRAINED but not TRAINED groups. No changes in sense of muscular effort were measured.

CONCLUSION

The smaller initial muscle size or sex-specific factors attenuated muscle loss but not strength or endurance losses in females during disuse. Resistance training before disuse may attenuate the loss in muscular endurance.

Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains

The purpose of this study was to examine the efficacy of 11 wk of resistance training to failure vs. nonfailure, followed by an identical 5-wk peaking period of maximal strength and power training for both groups as well as to examine the underlying physiological changes in basal circulating anabolic and catabolic hormones. Forty-two physically active men were matched and then randomly assigned to either a training to failure (RF; n = 14), nonfailure (NRF; n = 15), or control groups (C; n = 13). Muscular and power testing and blood draws to determine basal hormonal concentrations were conducted before the initiation of training (T0), after 6 wk of training (T1), after 11 wk of training (T2), and after 16 wk of training (T3). Both RF and NRF resulted in similar gains in 1-repetition maximum bench press (23 and 23%) and parallel squat (22 and 23%), muscle power output of the arm (27 and 28%) and leg extensor muscles (26 and 29%), and maximal number of repetitions performed during parallel squat (66 and 69%). RF group experienced larger gains in the maximal number of repetitions performed during the bench press. The peaking phase (T2 to T3) after NRF resulted in larger gains in muscle power output of the lower extremities, whereas after RF it resulted in larger gains in the maximal number of repetitions performed during the bench press. Strength training leading to RF resulted in reductions in resting concentrations of IGF-1 and elevations in IGFBP-3, whereas NRF resulted in reduced resting cortisol concentrations and an elevation in resting serum total testosterone concentration. This investigation demonstrated a potential beneficial stimulus of NRF for improving strength and power, especially during the subsequent peaking training period, whereas performing sets to failure resulted in greater gains in local muscular endurance. Elevation in IGFBP-3 after resistance training may have been compensatory to accommodate the reduction in IGF-1 to preserve IGF availability.

Possible Stimuli for Strength and Power Adaptation

The endocrine system plays an important role in strength and power development by mediating the remodelling of muscle protein. Resistance training scheme design regulates muscle protein turnover by modifying the anabolic (testosterone, growth hormone) and catabolic (cortisol) responses to a workout. Although resistance exercise increases the concentrations of insulin-like growth factor 1 in blood following exercise, the effect of scheme design is less clear, most likely due to the different release mechanisms of this growth factor (liver vs muscle). Insulin is non-responsive to the exercise stimulus, but in the presence of appropriate nutritional intake, elevated blood insulin levels combined with resistance exercise promotes protein anabolism. Factors such as sex, age, training status and nutrition also impact upon the acute hormonal environment and, hence, the adaptive response to resistance training. However, gaps within research, as well as inconsistent findings, limit our understanding of the endocrine contribution to adaptation. Research interpretation is also difficult due to problems with experimental design (e.g. sampling errors) and various other issues (e.g. hormone rhythms, biological fluid examined). In addition to the hormonal responses to resistance exercise, the contribution of other acute training factors, particularly those relating to the mechanical stimulus (e.g. forces, work, time under tension) must also be appreciated. Enhancing our understanding in these areas would also improve the prescription of resistance training for stimulating strength and power adaptation.

Effects of low-intensity resistance exercise with slow movement and tonic force generation on muscular function in young men

We investigated the acute and long-term effects of low-intensity resistance exercise (knee extension) with slow movement and tonic force generation on muscular size and strength. This type of exercise was expected to enhance the intramuscular hypoxic environment that might be a factor for muscular hypertrophy. Twenty-four healthy young men without experience of regular exercise training were assigned into three groups (n = 8 for each) and performed the following resistance exercise regimens: low-intensity [ approximately 50% of one-repetition maximum (1RM)] with slow movement and tonic force generation (3 s for eccentric and concentric actions, 1-s pause, and no relaxing phase; LST); high-intensity ( approximately 80% 1RM) with normal speed (1 s for concentric and eccentric actions, 1 s for relaxing; HN); low-intensity with normal speed (same intensity as for LST and same speed as for HN; LN). In LST and HN, the mean repetition maximum was 8RM. In LN, both intensity and amount of work were matched with those for LST. Each exercise session consisting of three sets was performed three times a week for 12 wk. In LST and HN, exercise training caused significant (P < 0.05) increases in cross-sectional area determined with MRI and isometric strength (maximal voluntary contraction) of the knee extensors, whereas no significant changes were seen in LN. Electromyographic and near-infrared spectroscopic analyses showed that one bout of LST causes sustained muscular activity and the largest muscle deoxygenation among the three types of exercise. The results suggest that intramuscular oxygen environment is important for exercise-induced muscular hypertrophy.

Metabolic and hormonal changes of severely burned children receiving long-term oxandrolone treatment

OBJECTIVE

When given to children for 1 year after a severe burn, oxandrolone significantly improves lean body mass, bone mineral content, and muscle strength. The beneficial effects of oxandrolone on height and weight were observed 1 year after treatment was discontinued. To study the efficacy of oxandrolone in severely burned children for 12 months after burn and 12 months after the drug was discontinued.

SUMMARY BACKGROUND DATA

Oxandrolone attenuates body catabolism during the acute phase after burn. It is unclear whether oxandrolone would have any beneficial effects during long-term treatment or if there were any effects after the drug was stopped.

METHODS

Sixty-one children with 40% total body surface area burns were enrolled in this study. Patients were randomized into those to receive oxandrolone (n = 30) or placebo (n = 31) for the first 12 months. Treatment was discontinued after 12 months, and the patients were studied without the drug for the following 12 months. At discharge and 6, 12, 18, and 24 months after burn, height, weight, body composition, resting energy expenditure, muscle strength, and serum human growth hormone, insulin-like growth factor-I (IGF-1), IGF binding protein-3, insulin, cortisol, parathyroid hormone, tri-iodothyronine uptake (T3 uptake), and free thyroxine index (FTI) were measured. Statistical analysis used Tukey multiple comparison test. Significance was accepted at P < 0.05.

RESULTS

Oxandrolone improved lean body mass, bone mineral content and muscle strength compared with controls during treatment, P < 0.05. Serum IGF-1, T3 uptake, and FTI were significantly higher during drug treatment compared with controls, P < 0.05. Significant increases in height and weight with oxandrolone were observed after the end of treatment.

CONCLUSIONS

Oxandrolone improved body composition and strength in severely burned children during the 12 months of treatment. Its effect on height and weight continued after treatment was discontinued.

Childhood obesity and socioeconomic status: a novel role for height growth limitation

OBJECTIVE

To assess prevalence and socioeconomic context of overweight and obesity in a cohort of Scottish children.

DESIGN

Cross-sectional study.

SETTING

Primary schools in Dundee, Angus, and Fife, Eastern Scotland, UK.

PARTICIPANTS

A total of 1240 boys and 1214 girls aged between 4-10 y.

MAIN OUTCOME MEASURE

Weight, height and body mass index (weight/height2).

RESULTS

Overall overweight or obesity prevalence was 24.6%, while prevalence of obesity alone was 6.1%. Individuals from schools with a high level of low-income families were 65% more likely to be overweight as judged by BMI. However, these children weighed the same as more affluent children of the same age, but were 1.26 cm shorter.

CONCLUSION

These data confirm the continued increase in childhood obesity in the UK and reveal a role for height-growth limitation in the absence of overall growth restriction, among children from low-income groups. This observation raises important questions regarding socioeconomic environmental factors in promoting the currently increasing levels of obesity.