Growth hormone pulsatility profile characteristics following acute heavy resistance exercise.

This investigation examined the hypothesis that acute heavy resistance exercise (AHRE) would increase overnight concentrations of circulating human growth hormone (hGH). Ten men (22 +/- 1 yr, 177 +/- 2 cm, 79 +/- 3 kg, 11 +/- 1% body fat) underwent two overnight blood draws sampled every 10 min from 1700 to 0600: a control and an AHRE condition. The AHRE was conducted from 1500 to 1700 and was a high-volume, multiset exercise bout. Three different immunoassays measured hGH concentrations: the Nichols immunoradiometric assay (Nichols IRMA), National Institute of Diabetes and Digestive and Kidney Diseases radioimmunoassay (NIDDK RIA), and the Diagnostic Systems Laboratory immunofunctional assay (DSL IFA). The Pulsar peak detection system was used to evaluate the pulsatility profile characteristics of hGH. Maximum hGH was lower in the exercise (10.7 microg/l) vs. the control (15.4 microg/l) condition. Mean pulse amplitude was lower in the exercise vs. control condition when measured by the Nichols IRMA and the DSL IFA. A differential pattern of release was also observed after exercise in which hGH was lower in the first half of sleep but higher in the second half. We conclude that AHRE does influence the temporal pattern of overnight hGH pulsatility. Additionally, because of the unique molecular basis of the DSL IFA, this influence does have biological relevance because functionally intact molecules are affected.     

Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion.

Hormonal and inflammatory responses to low-intensity resistance exercise with vascular occlusion were studied. Subjects (n = 6) performed bilateral leg extension exercise in the seated position, with the proximal end of their thigh compressed at 214 +/- 7.7 (SE) mmHg throughout the session of exercise by means of a pressure tourniquet. Mean intensity and quantity of the exercise were 20% of 1 repetition maximum and 14 repetitions x 5 sets, respectively. In each set, the subjects repeated the movement until exhaustion. Plasma concentrations of growth hormone (GH), norepinephrine (NE), lacate (La), lipid peroxide (LP), interleukin-6 (IL-6), and activity of creatine phosphokinase (CPK) were measured before and after the exercise was finished and the tourniquet was released. Concentrations of GH, NE, and La consistently showed marked, transient increases after the exercise with occlusion, whereas they did not change a great deal after the exercise without occlusion (control) done at the same intensity and quantity. Notably, concentration of GH reached a level approximately 290 times as high as that of the resting level 15 min after the exercise. IL-6 concentration showed a much more gradual increase and was maintained at a slightly higher level than in the control even 24 h after exercise. Concentrations of LP and CPK showed no significant change. The results suggest that extremely light resistance exercise combined with occlusion greatly stimulates the secretion of GH through regional accumulation of metabolites without considerable tissue damage.     

Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women

Kraemer, R. R., L. G. Johnson, R. Haltom, G. R. Kraemer, H. Gaines, M. Drapcho, T. Gimple, and V. Daniel Castracane. Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women. J. Appl.Physiol. 84(2): 703-708, 1998.Exercise elevatesgrowth hormone (GH) and prolactin (PRL) blood concentrations inpremenopausal women. Postmenopausal women taking hormone replacementtherapy (HRT) maintain higher estrogen levels that could affect GH andPRL. The purpose of the study was to determine the effects of HRT on GHand PRL responses to treadmill exercise. Seventeen healthy women whowere postmenopausal (naturally or surgically) [8 on HRT; 9 not onHRT (NHRT)], completed 30 min of treadmill exercise at 79.16 ± 1.2% maximal O₂ consumption (HRT group) and 80.19 ± 0.91% maximalO₂ consumption (NHRT group). Bloodsamples were collected from an intravenous catheter during an exercisesession and during a control session without exercise. GH and PRLconcentrations were significantly higher in the exercise trial than inthe nonexercise trial, whereas resting concentrations were similar forboth trials. GH and PRL peaked at 10.8 ± 1.60 and 12.67 ± 2.58 ng/ml, respectively, for HRT subjects and at 4.90 ± 1.18 and 9.04 ± 2.17 ng/ml, respectively, for NHRT subjects. GH concentrations inthe exercise trial were significantly higher for HRT than for NHRTsubjects. This is the first study to demonstrate that HRT enhancestreadmill-exercise-induced GH release and that similar PRL responses totreadmill exercise occur in postmenopausal women regardless of HRTstatus.

     

Hormonal and growth factor responses to heavy resistance exercise protocols

To examine endogenous anabolic hormone and growth factor responses to various heavy resistance exercise protocols (HREPs), nine male subjects performed each of six randomly assigned HREPs, which consisted of identically ordered exercises carefully designed to control for load [5 vs. 10 repetitions maximum (RM)], rest period length (1 vs. 3 min), and total work effects. Serum human growth hormone (hGH), testosterone (T), somatomedin-C (SM-C), glucose, and whole blood lactate (HLa) concentrations were determined preexercise, midexercise (i.e., after 4 of 8 exercises), and at 0, 5, 15, 30, 60, 90, and 120 min postexercise. All HREPs produced significant (P less than 0.05) temporal increases in serum T concentrations, although the magnitude and time point of occurrence above resting values varied across HREPs. No differences were observed for T when integrated areas under the curve (AUCs) were compared. Although not all HREPs produced increases in serum hGH, the highest responses were observed consequent to the H10/1 exercise protocol (high total work, 1 min rest, 10-RM load) for both temporal and time integrated (AUC) responses. The pattern of SM-C increases varied among HREPs and did not consistently follow hGH changes. Whereas temporal changes were observed, no integrated time (AUC) differences between exercise protocols occurred. These data indicate that the release patterns (temporal or time integrated) observed are complex functions of the type of HREPs utilized and the physiological mechanisms involved with determining peripheral circulatory concentrations (e.g., clearance rates, transport, receptor binding). All HREPs may not affect muscle and connective tissue growth in the same manner because of possible differences in hormonal and growth factor release.     

Release of luteinizing hormone and growth hormone after recovery from maximal exercise

Pulsatile properties of luteinizing hormone (LH) and growth hormone (GH) release were evaluated in 19 eumenorrheic untrained females [mean age 31.1 +/- 1.1 yr, height 165.2 +/- 1.4 cm, weight 64.8 +/- 2.1 kg, peak oxygen uptake (Vo2) 41.6 +/- 1.4 (SE) ml.kg-1.min-1] during the early follicular phase of the menstrual cycle (days 3-4 after the onset of menses). Each subject was studied during two consecutive menstrual cycles under each of two conditions in random order: 1) no formal exercise for 72 h (C) and 2) 12-24 h after two maximal exercise bouts (peak Vo2/lactate threshold treadmill evaluation and a 3,200-m time-trial run or a maximal Vo2 inclined treadmill test) performed on consecutive days (EX). Blood sampling was performed every 10 min for 12 h. LH and GH pulsatile parameters were identified and characterized by the Cluster pulse detection algorithm. No significant differences were noted in the number of peaks, peak amplitude, interpeak interval, peak increment, or 12-h integrated concentrations between C and EX for LH or GH. We conclude that maximal exercise protocols typically used for exercise evaluation do not have an effect on the pulsatile characteristics of LH or GH release in untrained women during the early follicular phase of the menstrual cycle if 12-24 h of recovery are allowed before evaluation of the pulsatile secretion of gonadotropins or GH.     

Postactivation potentiation effects after heavy resistance exercise on running speed

The purpose of this study was to investigate the postactivation potentiation effect after a heavy resistance stimulus (HRS) on running speed (RS). Fifteen amateur team game players (basketball, volleyball, handball, and soccer players), ages 18-23 years running the 30-m dash and the intermediate phase of 0-10 and 0-30 m sprints, were used to evaluate RS. Resistance training consisted of 10 single repetitions at 90% of 1 repetition maximum. The running tests were performed 3 times--(a) 3 minutes prior the HRS, (b) 3 minutes after the HRS, and (c) 5 minutes after the HRS--in separated training sessions. Results showed that RS was not affected 3 minutes after the resistance training, but it increased for both selected running phases (0-10 and 0-30 m) 5 minutes after the HRS (p < 0.05). These findings indicate that heavy resistance exercise improves 10- and 30-m sprint performance when performed 5 minutes after the exercise bout.     

Oral arginine attenuates the growth hormone response to resistance exercise.

This study investigated the combined effect of resistance exercise and arginine ingestion on spontaneous growth hormone (GH) release. Eight healthy male subjects were studied randomly on four separate occasions [placebo, arginine (Arg), placebo + exercise (Ex), arginine + exercise (Arg+Ex)]. Subjects had blood sampled every 10 min for 3.5 h. After baseline sampling (30 min), subjects ingested a 7-g dose of arginine or placebo (blinded, randomly assigned). On the exercise days, the subject performed 3 sets of 9 exercises, 10 repetitions at 80% one repetition maximum. Resting GH concentrations were similar on each study day. Integrated GH area under the curve was significantly higher on the Ex day (508.7 +/- 169.6 min.ng/ml; P < 0.05) than on any of the other study days. Arg+Ex (260.5 +/- 76.8 min.ng/ml) resulted in a greater response than the placebo day but not significantly greater than the Arg day. The GH half-life and half duration were not influenced by the stimulus administered. The GH secretory burst mass was larger, but not significantly, on the Arg, Ex, and Arg+Ex day than the placebo day. Endogenous GH production rate (Ex > Arg+Ex > Arg > placebo) was greater on the Ex and Arg+Ex day than on the placebo day (P < 0.05) but there were no differences between the Ex and Arg+Ex day. Oral arginine alone (7 g) stimulated GH release, but a greater GH response was seen with exercise alone. The combined effect of arginine before exercise attenuates the GH response. Autonegative feedback possibly causes a refractory period such that when the two stimuli are presented there will be suppression of the somatotrope.     

Serum leptin responses after acute resistance exercise protocols.

This study examined the acute effects of maximum strength (MS), muscular hypertrophy (MH), and strength endurance (SE) resistance exercise protocols on serum leptin. Ten young lean men (age = 23 +/- 4 yr; body weight = 79.6 +/- 5.2 kg; body fat = 10.2 +/- 3.9%) participated in MS [4 sets x 5 repetitions (reps) at 88% of 1 repetition maximum (1 RM) with 3 min of rest between sets], MH (4 sets x 10 reps at 75% of 1 RM with 2 min of rest between sets), SE (4 sets x 15 reps at 60% of 1 RM with 1 min of rest between sets), and control (C) sessions. Blood samples were collected before and immediately after exercise and after 30 min of recovery. Serum leptin at 30 min of recovery exhibited similar reductions from baseline after the MS (-20 +/- 5%), MH (-20 +/- 4%), and SE (-15 +/- 6%) protocols that were comparable to fasting-induced reduction in the C session (-12 +/- 3%) (P < 0.05). Furthermore, no differences were found in serum leptin among the MS, MH, SE, and C sessions immediately after exercise and at 30 min of recovery (P > 0.05). Cortisol was higher (P < 0.05) after the MH and SE protocols than after the MS and C sessions. Glucose and growth hormone were higher (P < 0.05) after exercise in the MS, MH, and SE protocols than after the C session. In conclusion, typical resistance exercise protocols designed for development of MS, MH, and SE did not result in serum leptin changes when sampled immediately or 30 min postexercise.     

Effects of dehydration on cerebrovascular control during standing after heavy resistance exercise

We tested the hypothesis that dehydration exacerbates reductions of middle cerebral artery blood velocity (MCAv) and alters cerebrovascular control during standing after heavy resistance exercise. Ten males participated in two trials under 1) euhydration (EUH) and 2) dehydration (DEH; fluid restriction + 40 mg furosemide). We recorded finger photoplethysmographic arterial pressure and MCAv (transcranial Doppler) during 10 min of standing immediately after high-intensity leg press exercise. Symptoms (e.g., lightheadedness) were ranked by subjects during standing (1-5 scale). Low-frequency (LF) oscillations of mean arterial pressure (MAP) and mean MCAv were calculated as indicators of cerebrovascular control. DEH reduced plasma volume by 11% (P = 0.002; calculated from hemoglobin and hematocrit). During the first 30 s of standing after exercise, subjects reported greater symptoms during DEH vs. EUH (P = 0.05), but these were mild and resolved at 60 s. While MAP decreased similarly between conditions immediately after standing, MCAv decreased more with DEH than EUH (P = 0.02). With prolonged standing under DEH, mean MCAv remained below baseline (P ≤ 0.01), and below EUH values (P ≤ 0.05). LF oscillations of MAP were higher for DEH at baseline and during the entire 10 min of stand after exercise (P ≤ 0.057), while LF oscillations in mean MCAv were distinguishable only at baseline and 5 min following stand (P = 0.05). Our results suggest that mean MCAv falls below a "symptomatic threshold" in the acute phase of standing after exercise during DEH, although symptoms were mild and transient. During the prolonged phase of standing, increases in LF MAP and mean MCAv oscillations with DEH may help to maintain cerebral perfusion despite absolute MCAv remaining below the symptomatic threshold.     

Impact of acute exercise intensity on pulsatile growth hormone release in men.

To investigate the effects of exercise intensity on growth hormone (GH) release, 10 male subjects were tested on 6 randomly ordered occasions [1 control condition (C), 5 exercise conditions (Ex)]. Serum GH concentrations were measured in samples obtained at 10-min intervals between 0700 and 0900 (baseline) and 0900 and 1300 (exercise+ recovery). Integrated GH concentrations (IGHC) were calculated by trapezoidal reconstruction. During Ex subjects exercised for 30 min (0900-0930) at one of the following intensities [normalized to the lactate threshold (LT)]: 25 and 75% of the difference between LT and rest (0.25LT and 0.75LT, respectively), at LT, and at 25 and 75% of the difference between LT and peak (1.25LT and 1.75LT, respectively). No differences were observed among conditions for baseline IGHC. Exercise+recovery IGHC (mean +/- SE: C = 250 +/- 60; 0.25LT = 203 +/- 69; 0.75LT = 448 +/- 125; LT = 452 +/- 119; 1.25LT = 512 +/- 121; 1.75LT = 713 +/- 115 microg x l(-1) x min(-1)) increased linearly with increasing exercise intensity (P < 0.05). Deconvolution analysis revealed that increasing exercise intensity resulted in a linear increase in the mass of GH secreted per pulse and GH production rate [production rate increased from 16. 5 +/- 4.5 (C) to 32.1 +/- 5.2 microg x distribution volume(-1) x min(-1) (1.75LT), P < 0.05], with no changes in GH pulse frequency or half-life of elimination. We conclude that the GH secretory response to exercise is related to exercise intensity in a linear dose-response pattern in young men.     

Effects of ginseng ingestion on growth hormone, testosterone, cortisol, and insulin-like growth factor 1 responses to acute resistance exercise

Ginseng, an herbal plant, has been ingested by many athletes in Oriental regions of the world in order to improve stamina and to facilitate rapid recovery from injuries. However, adequate investigation has not been conducted to examine the ergogenic effects of ginseng. To examine the effects of ginseng supplements on hormonal status following acute resistance exercise, eight male college students were randomly given water (control; CON) or 20 g of ginseng root extract (GIN) treatment immediately after a standardized exercise bout. Venous blood samples were drawn before and immediately after exercise and at 4 time points during a 2-hour recovery period. Human growth hormone, testosterone, cortisol, and insulin-like growth factor 1 (IGF-1) levels were determined by radioimmunoassay. The responses of plasma hormones following ginseng consumption were not significant between CON and GIN treatments during the 2-hour recovery period. These results do not support the use of ginseng to promote an anabolic hormonal status following resistance exercise.     

Overnight responses of the circulating IGF-I system after acute, heavy-resistance exercise.

This study evaluated the individual components of the insulin-like growth factor I (IGF-I) system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2 and -3, and the acid-labile subunit (ALS)] in 10 young, healthy men (age: 22 +/- 1 yr, height: 177 +/- 2 cm, weight: 79 +/- 3 kg, body fat: 11 +/- 1%) overnight for 13 h after two conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex). The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-repetition maximum sets with 90-s rest periods between sets. The Ex was performed from 1500 to 1700; blood was obtained immediately postexercise and sampled throughout the night (every 10 min for the first hour and every hour thereafter) until 0600 the next morning. For the first hour, significant differences (P < or = 0.05) were only observed for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2 increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 microg/ml) after exercise. The results from this study suggest that the impact that resistance exercise exerts on the circulating IGF-I system is not in the alteration of the amount of IGF-I but rather of the manner in which IGF-I is partitioned among its family of binding proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system that can be detected in the systemic circulation.     

Acute hormone responses to heavy resistance lower and upper extremity exercise in young versus old men

Acute hormone responses of growth hormone (GH), total and free testosterone (TT and FT) and cortisol (C) to heavy resistance isometric exercise were examined in ten young men [YM 26.5 (SD 4.8) years] and ten old men [OM 70.0 (SD 3.7) years]. Loading conditions of the same relative intensity were created for the lower and upper extremity actions separately as well as for both of them together – lower extremity exercise (LE; knee extension), upper extremity exercise (UE; bench press extension), and lower and upper extremity exercise (LUE) performed simultaneously in a seated position. Single voluntary maximal isometric actions lasting for 5 s were performed repeatedly for ten repetitions (with a recovery of 5 s) for a total of four sets. The recovery time between the sets was 1 min. Each exercise led to large acute decreases in maximal isometric force in both YM (P < 0.001) and OM (P < 0.001) ranging from 41% to 26% with no significant differences between the groups. Serum GH concentrations increased in both YM (P < 0.05–0.01) and OM (P < 0.05) but the postexercise value in YM during LE was greater (P < 0.05) than for OM. The TT increased (P < 0.01–0.001) in YM in all three exercises, while in OM the increase occurred only during LE (P < 0.01). The exercises led to increases in FT in YM (P < 0.05 for LE and LUE), while in OM the increase occurred only during LUE (P < 0.05). The pre and postexercise FT were greater in YM (P < 0.001) than in OM. No significant changes occurred in C either in YM or in OM. The blood lactate concentrations increased during the exercises in both YM (P < 0.001) and OM (P < 0.05–0.001) but the postexercise values during LE and LUE in YM were greater (P < 0.05) than in OM. The present data would indicate that the responses of GH, TT and FT to heavy resistance isometric exercise are lowered with increasing age. The reduced acute hormone response together with the lowered basal values in FT in the older men compared to the young men may indicate decreased anabolic effects on muscles and may explain in part the loss of muscle mass and strength associated with aging. Accepted: 18 August 1997     

Recovery after heavy resistance exercise and skeletal muscle androgen receptor and insulin-like growth factor-I isoform expression in strength trained men

The effects of heavy resistance exercise on skeletal muscle androgen receptor (AR) protein concentration and mRNAs of AR, insulin-like growth factor-I (IGF)-IEa, and mechano growth factor (MGF) expression were examined from biopsies of vastus lateralis (VL) muscle before and 48 hours after heavy resistance exercise (5 × 10 repetition maximum [RM] leg press and 4 × 10RM squats) in 8 adult strength trained men. The present exercise induced an acute decrease in maximal isometric force and increased serum total testosterone (T) and free testosterone (FT) concentrations. During 2 recovery days, maximal isometric force and subjective perception of physical fitness remained significantly lowered, whereas serum creatine kinase activity, subjective muscle soreness, and muscle swelling (i.e., thickness of VL by ultrasound) were significantly increased compared to pre-exercise values. Subjective perception of physical fitness was followed up to 7 days, and by 6 days postexercise, it was elevated above the pre-exercise level. Basal T and FT concentrations remained unaltered after the exercise. No statistically significant changes were observed in AR protein or mRNA expression, but IGF-IEa (p < 0.05) and MGF (p < 0.05) mRNA expression were increased compared to pre-exercise levels. These findings indicate that IGF-IEa and MGF responses may be related to acute regenerative processes in muscle because of exercise and may contribute to muscular adaptation to resistance exercise. Subjective perception of physical fitness suggests that recovery over a pre-exercise level of the present type of heavy resistance exercise can take approximately 6 days.     

Time course of strength and echo intensity recovery after resistance exercise in women

The purpose of this study was to evaluate the time course responses of strength, delayed-onset muscle soreness (DOMS), muscle thickness (MT), circumference (CIRC), and ultrasonography echo intensity (EI) after a traditional hypertrophic isoinertial resistance training session in young women. Ten (22.0 ± 3.2 years) healthy, untrained volunteers participated in the study. The resistance exercise session consisted of 4 sets of 10 repetitions at 80% of 1 repetition maximum (1RM) of the dominant arm elbow flexors. Maximum isometric elbow flexion peak torque (PT) at 90°, MT, and EI were recorded for both arms at baseline (PRE), immediately after exercise (0 hours) and at 24, 48, and 72 hours after exercise. Comparisons were made using a 2 × 5 mixed factor analysis of variance. There was a significant (p < 0.05) loss in PT and increase in MT at 0, 24, 48, and 72 hours. In contrast, EI increased only after 24, 48, and 72 hours, not at 0 hours. There were no significant changes in PT, DOMS, MT, and EI in the nondominant (control) arm after the exercise protocol. Our data suggest that after 4 sets of 80% of 1RM of unilateral elbow flexion resistance exercise, nonresistance trained women need >72 hours to fully recover muscle strength, MT, CIRC, and EI. Furthermore, the EI appears to be a sensitive and reliable method to assess MD.     

The influence of recovery duration after heavy resistance exercise on sprint cycling performance

ABSTRACT: Thatcher, R, Gifford, R, and Howatson, G. The influence of recovery duration after heavy resistance exercise on sprint cycling performance. J Strength Cond Res 26(11): 3089-3094, 2012-The aim of this study was to determine the optimal recovery duration after prior heavy resistance exercise (PHRE) when performing sprint cycling. On 5 occasions, separated by a minimum of 48 hours, 10 healthy male subjects (mean ± SD), age 25.5 ± 7.7 years, body mass 82.1 ± 9.0 kg, stature 182.6 ± 87 cm, deadlift 1-repetition maximum (1RM) 142 ± 19 kg performed a 30-second sprint cycling test. Each trial had either a 5-, 10-, 20-, or 30-minute recovery after a heavy resistance activity (5 deadlift repetitions at 85% 1RM) or a control trial with no PHRE in random order. Sprint cycling performance was assessed by peak power (PP), fatigue index, and mean power output over the first 5 seconds (MPO5), 10 seconds (MPO10), and 30 seconds (MPO30). One-way analysis of variance with repeated measures followed by paired t-tests with a Bonferroni adjustment was used to analyze data. Peak power, MPO5, and MPO10 were all significantly different during the 10-minute recovery trial to that of the control condition with values of 109, 112, and 109% of control, respectively; no difference was found for the MPO30 between trials. This study supports the use of PHRE as a strategy to improve short duration, up to, or around 10-second, sprint activity but not longer duration sprints, and a 10-minute recovery appears to be optimal to maximize performance.     

Pulsatile growth hormone secretion persists in genetic growth hormone-releasing hormone resistance

Growth hormone (GH) secretion is regulated by GH-releasing hormone (GHRH), somatostatin, and possibly ghrelin, but uncertainty remains about the relative contributions of these hypophysiotropic factors to GH pulsatility. Patients with genetic GHRH receptor (GHRH-R) deficiency present an opportunity to examine GH secretory dynamics in the selective absence of GHRH input. We studied circadian GH profiles in four young men homozygous for a null mutation in the GHRH-R gene by use of an ultrasensitive GH assay. Residual GH secretion was pulsatile, with normal pulse frequency, but severely reduced amplitude (<1% normal) and greater than normal process disorder (as assessed by approximate entropy). Nocturnal GH secretion, both basal and pulsatile, was enhanced compared with daytime. We conclude that rhythmic GH secretion persists in an amplitude-miniaturized version in the absence of a GHRH-R signal. The nocturnal enhancement of GH secretion is likely mediated by decreased somatostatin tone. Pulsatility of residual GH secretion may be caused by oscillations in somatostatin and/or ghrelin; it may also reflect intrinsic oscillations in somatotropes.