Comparison of hormone responses following light resistance exercise with partial vascular occlusion and moderately difficult resistance exercise without occlusion

Previous studies of contracting muscle with low loading and partial vascular occlusion demonstrated hypertrophy and strength adaptations similar to and exceeding those observed with traditional moderate to high resistance (Shinohara M, Kouzaki M, Yoshihisa T, and Fukunaga T. Eur J Physiol 77: 189-191, 1998; Takarada Y, Takazawa H, Sato Y, Takebayashi S, Tanaka Y, and Ishii N. J Appl Physiol 88: 2097-2106, 2000; Takarada Y, Sato Y, and Ishii N. Eur J Physiol 86: 308-314, 2002). The purpose of the study was to determine the anabolic and catabolic hormone responses to light resistance exercise combined with partial vascular occlusion. Three experimental conditions of light resistance with partial occlusion (LRO), moderate resistance with no occlusion (MR), and partial occlusion without exercise (OO) were performed by eight healthy subjects [mean 21 yr (SD 1.8)]. Three sets of single-arm biceps curls and single-leg calf presses were completed to failure with 1-min interset rest periods. Workloads of 30 and 70% one repetition maximum for each exercise were lifted for the LRO and MR trials, respectively. Blood samples were taken preexercise, postexercise, and 15 min postexercise for each experimental condition. Lactate increased significantly in the LRO and MR trials and was not significantly different from each other at any time point. Growth hormone (GH) increased significantly by fourfold from pre- to postexercise in the LRO session but did not change significantly during this time period in the MR and OO trials (8.3 +/- 2.3 vs. 2.1 +/- 1.2 and 2.6 +/- 0.94 microg/l; respectively, P < 0.05). There were no changes in resting total testosterone [T; mean 15.7 +/- 1.6 (SE) nmol/l], free testosterone (FT; 54.1 +/- 4.5 pmol/l), or cortisol (267.6 +/- 22 nmol/l) across all trials and times. In conclusion, with similar lactate responses, light exercise combined with partial vascular occlusion elicits a greater GH response than moderate exercise without occlusion but does not affect T, FT, or cortisol.

Validity of Wearable Activity Monitors during Cycling and Resistance Exercise

INTRODUCTION

The use of wearable activity monitors has seen rapid growth; however, the mode and intensity of exercise could affect the validity of heart rate (HR) and caloric (energy) expenditure (EE) readings. There is a lack of data regarding the validity of wearable activity monitors during graded cycling regimen and a standard resistance exercise. The present study determined the validity of eight monitors for HR compared with an ECG and seven monitors for EE compared with a metabolic analyzer during graded cycling and resistance exercise.

METHODS

Fifty subjects (28 women, 22 men) completed separate trials of graded cycling and three sets of four resistance exercises at a 10-repetition-maximum load. Monitors included the following: Apple Watch Series 2, Fitbit Blaze, Fitbit Charge 2, Polar H7, Polar A360, Garmin Vivosmart HR, TomTom Touch, and Bose SoundSport Pulse (BSP) headphones. HR was recorded after each cycling intensity and after each resistance exercise set. EE was recorded after both protocols. Validity was established as having a mean absolute percent error (MAPE) value of ≤10%.

RESULTS

The Polar H7 and BSP were valid during both exercise modes (cycling: MAPE = 6.87%, R = 0.79; resistance exercise: MAPE = 6.31%, R = 0.83). During cycling, the Apple Watch Series 2 revealed the greatest HR validity (MAPE = 4.14%, R = 0.80). The BSP revealed the greatest HR accuracy during resistance exercise (MAPE = 6.24%, R = 0.86). Across all devices, as exercise intensity increased, there was greater underestimation of HR. No device was valid for EE during cycling or resistance exercise.

CONCLUSIONS

HR from wearable devices differed at different exercise intensities; EE estimates from wearable devices were inaccurate. Wearable devices are not medical devices, and users should be cautious when using these devices for monitoring physiological responses to exercise.

Leptin and exercise

Short-term exercise (<60 min) studies suggest that leptin concentrations are not acutely affected in healthy males and females. Most reports of reductions in serum leptin may be attributed to circadian rhythms or hemoconcentration. For long-term (> or =60 min) exercise, a reduction in leptin concentrations reported from 1 to 3 hr of running or cycling has been attributed to diurnal reduction in circulating leptin, independent of exercise. Exercise that produces a sufficient energy imbalance (kilocalorie intake versus kilocalorie expenditure) suppresses 24-hr mean and amplitude of the diurnal rhythm of leptin in women. Suppression of leptin concentrations may be counterbalanced by feeding and may explain consistent reports of reductions in leptin concentrations following extreme bouts of exercise such as marathons or ultramarathons. In addition, leptin concentrations are reduced 48 hr after long-term aerobic exercise and long-term resistance exercise is associated with delayed leptin reduction 9 hr postexercise. Training studies have documented that short-term exercise training (< or =12 weeks) does not affect leptin levels, with the exception of patients with type 2 diabetes. Exercise training protocols that result in reduced fat mass will lower leptin concentrations, thus, most investigators have reported leptin concentrations after accounting for fat loss. There are disparate findings concerning long-term (>12 weeks) training studies, with a number of studies finding no effect of training on leptin concentrations other than effects induced by fat loss, and other studies finding reductions in leptin concentrations after accounting for fat loss. Exercise training-induced reductions in leptin levels have been attributed to alterations in energy balance, improvements in insulin sensitivity, alterations in lipid metabolism, and unknown factors. Hormone replacement does not seem to affect leptin adaptations to training. Patients with type 2 diabetes show delayed effects of short-term resistance exercise on leptin concentrations, reduced leptin levels with long-term training, and appear to be more sensitive to training-induced leptin adaptations than other populations.

Serum leptin concentration in women: effect of age, obesity, and estrogen administration

OBJECTIVE

To compare serum leptin levels in normally cycling reproductive females (20-35 years old) with those in age-matched males, in women who were receiving oral contraceptives, and in older (postmenopausal) women (50-65 years old) who were or who were not receiving hormone replacement therapy.

DESIGN

Case-control study.

SETTING

Obstetrics and Gynecology Clinic, Texas Tech University Health Sciences Center-Amarillo, or the Exercise Physiology Laboratory at Southeastern Louisiana University.

PATIENT(S)

Normally cycling women between the ages of 20-35 years and age-matched controls who were receiving oral contraceptives. Postmenopausal women between the ages of 50-65 years who were or who were not receiving hormone replacement therapy.

MAIN OUTCOME MEASURE(S)

Serum leptin concentration.

RESULT(S)

In all groups, serum leptin concentrations were correlated significantly with body mass index. Leptin levels were significantly higher in young women than young men (P <.001), but no other statistically significant differences were found for the other three comparisons.

CONCLUSION(S)

Serum leptin concentrations expressed as a measure of adiposity (body mass index) are greater in young normally cycling females (20-35 years old) than in age-matched males. There is no difference in levels of serum leptin between young and postmenopausal (50-65 years old) women. Estrogen administration, either in young women who are receiving estrogen-progestin oral contraceptives or in postmenopausal women who are receiving hormone replacement therapy, does not effect serum leptin concentrations.

Rigorous Running Increases Growth Hormone and Insulin-Like Growth Factor-I Without Altering Ghrelin

It has been suggested that ghrelin may play a role in growth hormone (GH) responses to exercise. The present study was designed to determine whether ghrelin, GH, insulin-like growth factor-I (IGF-I), and IGF-binding protein-3 (IGFBP-3) were altered by a progressively intense running protocol. Six well-trained male volunteers completed a progressively intense intermittent exercise trial on a treadmill that included four exercise intensities: 60%, 75%, 90%, and 100% of Vo2max. Blood samples were collected before exercise, after each exercise intensity, and at 15 and 30 mins following the exercise protocol. Subjects also completed a separate control trial at the same time of day that excluded exercise. GH changed significantly over time, and GH area under the curve (AUC) was significantly higher in the exercise trial than the control trial. Area under the curve IGF-I levels for the exercise trial were significantly higher than the control trial. There was no difference in the ghrelin and IGFBP-3 responses to the exercise and control trials. Pearson correlation coefficients revealed significant relationships between ghrelin and both IGF-I and IGFBP-3; however, no relationship between ghrelin and GH was found. In conclusion, intense running produces increases in total IGF-I concentrations, which differs from findings in previous studies using less rigorous running protocols and less frequent blood sampling regimens. Moreover, running exercise that produces substantial increases in GH does not affect peripheral ghrelin levels; however, significant relationships between ghrelin and both IGF-I and IGFBP-3 exist during intense intermittent running and recovery, which warrants further investigation.

A transient elevated irisin blood concentration in response to prolonged, moderate aerobic exercise in young men and women

Irisin, a newly discovered, PGC-1α dependent myokine, has recently been shown to increase in circulation in response to sprint exercise. This study examined the effect of prolonged exercise on irisin concentrations in young men (n=7) as well as in young women (n=5) during different stages of the menstrual cycle. Seven young men completed 90 min of treadmill exercise at 60% of VO2max and a resting control trial. Five women completed the same exercise protocol in two different trials: during the early follicular phase and mid-luteal phase of the menstrual cycle. Blood samples were collected and analyzed for irisin concentrations immediately before exercise, at 54 and 90 min of exercise, and at 20 min of recovery (R20). Findings revealed that by 54 min of a 90 min treadmill exercise protocol at 60% of VO2max, irisin concentrations significantly increased 20.4% in young men and 20.3% as well as 24.6% in young women during the early follicular and mid-luteal phases of the menstrual cycle, respectively. However, by 90 min of exercise as well as R20, irisin concentrations were no longer elevated. Stage of the menstrual cycle did not affect responses in young women. Findings indicate that prolonged aerobic exercise produces a transient increase in irisin concentrations during the first hour of exercise for both genders and suggest that this form of moderate exercise may be helpful in improving fat metabolism.

RPE, pain, and physiological adjustment to concentric and eccentric contractions

PURPOSE

The purpose of the study was to compare perceptual (RPE and pain), cardiac (heart rate), lactate, and endocrine (cortisol) responses with concentric (CON) and eccentric (ECC) resistance exercise protocols using the same absolute workload.

METHODS

Eight healthy men with resistance-training experience participated in the study. Subjects completed two experimental trials consisting of either CON contractions or ECC contractions at the same absolute workload for each of four exercises: bench press, leg extension, military press, and leg curl. Subjects performed four sets of 12 repetitions at 80% of 10-RM with 90-s rest periods. Blood samples were taken before, immediately after, and 15-min postexercise.

RESULTS

There was a significant trial effect for RPE, with CON exercise eliciting a higher RPE than ECC exercise (6.71 +/- 0.51 and 4.10 +/- 0.27, respectively). A significant trial effect was also demonstrated for pain, with CON exercise producing a higher pain rating than ECC exercise (5.59 +/- 0.41 and 3.23 +/- 0.27, respectively). Significantly higher heart rates and lactates were also demonstrated during the CON trial. For cortisol, a significant interaction was revealed between the pre- and immediate posttrial measures but not an overall trial effect. Correlational analyses revealed a significant relationship between RPE and pain for both trials.

CONCLUSIONS

CON exercise elicits greater perceptual (higher RPE and pain rating), cardiac, lactate and cortisol response than ECC exercise at the same absolute workload. Data demonstrate that relative to absolute load, RPE and pain respond to resistance exercise in a similar fashion. Additionally, physiological cues are consistent with these perceptual data.

Adiponectin responses to continuous and progressively intense intermittent exercise

PURPOSE

Adiponectin is a recently discovered adipocyte protein that is lower in patients with coronary artery disease and in Type II diabetics who have insulin resistance. Regular exercise is known to be a preventative factor in the development of atherosclerosis and Type II diabetes. Acute exercise increases insulin sensitivity; however, it also increases beta-adrenergic and glucocorticoid activities that may suppress adiponectin expression. Two experiments were conducted to determine whether acute exercise affects adiponectin concentrations.

METHODS

In the first experiment, six healthy male subjects completed 30 min of heavy continuous running exercise at 79% of VO (2max). In the second experiment, well-trained runners completed strenuous intermittent exercise consisting of treadmill running at 60, 75, 90, and 100% VO (2max). A resting control trial for the second experiment was also conducted.

RESULTS

Glucose and insulin were not altered significantly in the first experiment, but both increased significantly (P < 0.05) in the second experiment. A significant increase (P < 0.05) in adiponectin in the first experiment was no longer significant after correction for plasma volumes shifts. In the second experiment, there were significant (P < 0.05) changes in adiponectin concentrations over time but not a significant difference between adiponectin responses in exercise and control trials.

CONCLUSIONS

The data suggest that 30 min of heavy continuous running or more strenuous intermittent running does not stimulate an increase in production and release of adiponectin, and small increases in adiponectin concentrations resulting from the exercise may be attributed to normal plasma volume shifts.

Circuit weight training and its effects on excess postexercise oxygen consumption

OBJECTIVE

There is a paucity of research concerning energy expenditure during and after circuit weight training (CWT). There is evidence that duration of rest between sets affects metabolic responses to resistive exercise. The purpose of the study was to determine the effect of rest-interval duration upon the magnitude of 1 h of excess postexercise oxygen consumption (EPOC).

METHODS

Seven healthy men completed two randomized circuit weight training sessions using 20-s and 60-s rest intervals (20 RI, 60 RI). Sessions included two circuits of eight upper and lower body resistive exercises in which 20 repetitions were performed at 75% of a previously determined 20 repetition maximum.

RESULTS

The 1 h EPOC of 10.3 +/- 0.57 L for the 20 RI session was significantly higher than 7.40 +/- 0.39 L for the 60 RI session. The net caloric expenditure during 1 h of recovery from the 20 RI session was significantly higher than that of the 60 RI session (51.51 +/- 2.84 vs 37.00 +/- 1.97 kcal); however, total gross energy expenditure (exercise + 1 h recovery) was significantly greater for the 60 RI protocol (277.23 kcal) than the 20 RI protocol (242.21 kcal).

CONCLUSION

Data demonstrate that shortening the rest interval duration will increase the magnitude of 1 h EPOC from CWT; however, the exercise + recovery caloric costs from CWT are slightly greater for a longer rest interval duration protocol. These data suggest that total caloric cost be taken into account for CWT.

Hormonal responses from concentric and eccentric muscle contractions

Intense resistance exercise can acutely increase testosterone (T), free testosterone (FT), and growth hormone (GH) concentrations, but there are few investigations concerning acute endocrine responses to concentric (CON) and eccentric (ECC) contractile actions.

PURPOSE

The purpose of the study was to compare acute anabolic hormonal responses to bouts of dynamic CON and ECC contractions from multiple exercises at the same absolute load.

METHODS

Ten young men (age: 24.7 +/- 1.2 yr, weight: 85.45 +/- 24.2 kg, and height: 178 +/- 0.2 cm) completed two trials in counterbalanced fashion consisting of only CON or ECC contractions at the same absolute workload. Subjects performed four sets of 12 repetitions of bench press, leg extension, military press, and leg curl at 80% of a 10-repetition maximum with 90-s rest periods. Blood samples were collected pre-, post-, and 15-min postexercise.

RESULTS

There were significant increases in GH, T, and FT and lactate for both trials, but only GH and lactate were greater for the CON trial.

CONCLUSION

CON exercise increases GH concentrations to a much greater extent than ECC exercise at the same absolute load, and it is likely that greater GH responses were related to intensity rather than mode of contraction. Also, CON and ECC dynamic contraction trials at the same absolute workload elicited similar small but significant increases in T and FT, indicating that the greater metabolic stress produced by during the CON trial did not affect these hormone responses.

Alterations in plasma-volume-corrected blood components of marathon runners and concomitant relationship to performance

The study was undertaken to determine the effects of running a marathon on concentration of various blood components resulting from phenomena other than fluid loss, and these were related to performance times. Twenty male marathon runners ranging from 20 to 50 years of age participated in the study. Blood samples were collected before and after the subjects ran in a marathon. Blood samples were analyzed for sodium, potassium, glucose, lactate dehydrogenase, creatinine, creatine phosphokinase, triglycerides, cholesterol, hematocrit, hemoglobin, protein, white blood cell number, uric acid, carbon dioxide, and iron. All of the blood parameters increased significantly in concentration with the exceptions of glucose and carbon dioxide which decreased. After accounting for plasma-volume loss (COR), there remained significant increases in blood serum lactate dehydrogenase, creatinine, creatine phosphokinase, uric acid, iron, and whole-blood white blood cell number. Significant decreases in COR serum sodium, protein, glucose, and carbon dioxide were found. Lactate dehydrogenase and creatine phosphokinase concentration changes support the concept of acute damage to muscle tissue resulting from marathon running. No strong relationship between performance time and other measured variables was found. COR measures were more representative of marathon induced blood changes from physiological dynamics other than plasma volume change than presently reported findings.

Relative energy deficiency in sports (RED-S): elucidation of endocrine changes affecting the health of males and females

The purpose of this review is to present a different perspective of the relative energy deficiency syndrome, to improve understanding of associated endocrine alterations, and to highlight the need for further research in this area. The term "female athlete triad" was coined over 25 years ago to describe three interrelated components: disordered eating, menstrual dysfunction, and low bone mass. The syndrome's etiology is attributed to energy intake deficiency relative to energy expenditure required for health, function, and daily living. Recently, it became clear that there was a need to broaden the term, as the disorder is not an issue of only three interrelated problems but of a whole spectrum of insults resulting from low energy availability (LEA; i.e., insufficient energy availability to cover basic physiological demands) that can potentially affect any exerciser, irrespective of gender. The new model, termed relative energy deficiency in sport (RED-S), has received greater scrutiny in sports medicine due to its effects on both health and performance in athletes of both sexes. RED-S results from low-energy diets (intentional or unintentional) and/or excessive exercise. Energy deficiency reduces hypothalamic pulsatile release of gonadotropin-releasing hormone, this impairing anterior pituitary release of gonadotropins. In women, reduced FSH and LH pulsatility produces hypoestrogenism, causing functional hypothalamic amenorrhea and decreased bone mass. In men, it reduces testosterone and negatively affects bone health. Moreover, LEA alters other hormonal pathways, causing physiological consequences, such as alteration of the thyroid hormone signaling pathways, leptin levels, carbohydrate metabolism, the growth hormone/insulin-like growth factor-1 axis, and sympathetic/parasympathetic tone. This review explains and clarifies the effects of RED-S in both sexes.

Ghrelin and other glucoregulatory hormone responses to eccentric and concentric muscle contractions

OBJECTIVE

Heavy resistance exercise increases growth hormone (GH) and blood glucose levels. Ghrelin is an endogenous ligand for the GH secretagory receptor that stimulates growth hormone release. Circulating ghrelin levels are suppressed by insulin and glucose. The study was conducted to determine effects of concentric (CON) and eccentric (ECC) muscle actions at the same absolute workload on circulating ghrelin and glucose as well as related glucoregulatory peptides.

METHODS

Ten-RM loads for bench press, leg extension, military press, and leg curl were obtained from nine males, mean age 25. +/- 1.2 yr and body fat 17.2 +/- 1.6%. Subjects then completed two experimental trials of either CON or ECC contractions at the same absolute workload. Subjects performed four sets of 12 repetitions for each exercise at 80% of a 10-RM with 90 s rest periods. A pulley system or steel levers were positioned on each machine to raise or lower the weight so only CON or ECC contractions were performed. Pre-, post-, and 15-min post-exercise blood samples were collected.

RESULTS

Ghrelin did not increase in response to either muscle action and actually declined during the CON trial. Glucose and insulin increased regardless of the form of muscle action, but amylin and C-peptide did not change.

CONCLUSIONS

Data indicate that ghrelin does not contribute to moderate resistance exercise-induced increases in growth hormone, whether from CON or ECC muscle actions. Results suggest that with a moderate loading protocol both CON and ECC muscle actions performed at the same absolute workload elevate glucose and insulin concentrations, but are not related to post-CON exercise ghrelin suppression.

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

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

Premenstrual syndrome: diagnosis and treatment experiences

We sought to examine the diagnosis and treatment experiences of women in the United States who reported having been diagnosed with premenstrual syndrome (PMS) by a physician. A survey of 220 women, randomly selected, ages 26-56, who subscribed to a woman's health newsletter and reported being given a diagnosis of PMS by a physician was conducted. Subjects reported (1) they sought medical help for 5.33 +/- 6.23 years before receiving a diagnosis, (2) they sought help from 3.75 +/- 3.22 physicians for PMS symptoms, (3) they thought the majority (71%) of physicians they used were not adequately informed to diagnose and treat them, (4) only a minority (23%) of physicians used a symptom chart, currently the only way to confirm a PMS diagnosis, when determining their diagnosis, and (5) only approximately 1 in 4 (26%) physicians provided them with a helpful treatment. Seventy-six percent of subjects reported that a PMS diagnosis resulted from their own suggestion, with an agreement by the physician. Eighty-one percent reported that the initial suggestion of PMS came from a non-medical source. The most commonly recommended and used treatments were vitamins, exercise, and diet modification. Current treatment satisfaction was 15.6% not very satisfied, 48.8% somewhat satisfied, and 35% very satisfied. Satisfaction was higher if natural progesterone or hysterectomy with oophorectomy was included as a treatment, although a high percentage of satisfaction was seen with several treatments. Data indicate that physicians from whom most of the women sought care between 1974 and 1994 failed to recognize, diagnose, or treat their PMS using the standards and protocols published in the medical literature.

Effects of estrogen replacement therapy on dehydroepiandrosterone, dehydroepiandrosterone sulfate, and cortisol responses to exercise in postmenopausal women

OBJECTIVE

To determine the effects of hormone replacement therapy (HRT) on dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), and cortisol (F) responses to treadmill exercise.

DESIGN

Controlled clinical study.

SETTING

Female volunteers in an academic research environment.

PATIENT(S)

Sixteen healthy, postmenopausal women (7 were receiving HRT, 9 were not).

INTERVENTION(S)

Blood samples were taken from an intravenous catheter before, during, and after 30 minutes of treadmill exercise following an overnight fast. A second session was conducted one month later for the same subjects using the same blood sampling protocol without exercise.

MAIN OUTCOME MEASURE(S)

Serum DHEA, DHEAS, and F concentrations.

RESULT(S)

The HRT and untreated DHEA area under the curve (AUC) for the exercise trials was significantly greater than that for the control trials. The untreated, but not the HRT, DHEAS AUC for the exercise trials was significantly greater than that for the control trials. The HRT and untreated F AUC for the exercise trials was significantly greater than that for the control trials. The AUC for the HRT exercise trials was significantly higher than the untreated exercise trials for DHEA and F, but not DHEAS.

CONCLUSION(S)

Data suggest that treadmill exercise elevates DHEA, DHEAS, and F levels in postmenopausal women and that HRT enhances the DHEA and F responses.

Effects of treadmill running on plasma beta-endorphin, corticotropin, and cortisol levels in male and female 10K runners

Reports of plasma beta-endorphin (B-EN) levels in response to submaximal exercise have been highly disparate. Variations in experimental design have complicated interpretation of previous research. The present study was designed to determine whether a sequential change in plasma beta-endorphin (B-EN), corticotropin (ACTH), and cortisol levels occurs in response to a 30-min submaximal run. Twenty-three subjects were divided into four groups: male runners, female runners, sedentary males and sedentary females. Subjects ran on a treadmill at 80% of previously determined maximum heart rate. Five plasma samples were obtained through an indwelling catheter before exercise (-30 and 0 min), at 15 and 30 min of exercise, and after 30 minutes of recovery. The run resulted in no rise in B-EN, ACTH, and cortisol despite an elevated rectal temperature. B-EN values were significantly higher in males than in females (p less than 0.01). No sex or training differences were seen with respect to change of hormone concentrations over the course of the run. Three male runners developed symptoms of vasovagal syncope after the catheter placement and had high initial B-EN, ACTH, and cortisol concentrations which decreased throughout the run. These data indicate that gender and training do not affect ACTH and cortisol concentrations before, during, and after 30 min of treadmill running at 80% of maximum heart rate, whereas B-EN concentrations are higher in males under these conditions.

Effects of aerobic exercise on serum leptin levels in obese women

It has been demonstrated that leptin concentrations in obese patients may be altered by weight loss. We examined the effects of a 9-week aerobic exercise program on serum leptin concentrations in overweight women (20-50% above ideal body mass) under conditions of weight stability. Sixteen overweight women, mean (SE) age 42.75 (1.64) years, comprised the exercise group which adhered to a supervised aerobic exercise program. A graded exercise treadmill test was conducted before and after the exercise program to determine maximal oxygen uptake (VO2max) using open-circuit spirometry. The women demonstrated improved aerobic fitness (VO2max increased 12.29%), however, body fat and the body mass index did not change significantly [42.27 (1.35)-41.87 (1.33)%]. Fourteen women, age 40.57 (2.80) years, did not exercise over the same time period and served as a control group. Serum leptin levels were not significantly altered for either the exercise [28.00 (2.13)-31.04 (2.71) ng x ml(-1)] or the control group [33.24 (3.78)-34.69 (3.14) ng x mg(-1)]. The data indicate that 9 weeks of aerobic exercise improves aerobic fitness, but does not affect leptin concentrations in overweight women.

Leptin and steroid hormone responses to exercise in adolescent female runners over a 7-week season

The purpose of the study was to investigate the responses of leptin and steroid hormones to maximal exercise in adolescent female runners over a competitive season. Seven adolescent female distance runners completed three testing trials during weeks 1.4 and 7 of their high-school track season. Blood samples were collected before and after a discontinuous graded exercise test to exhaustion (GXT) for each trial. Tests were administered during the subjects' normal training time (3:30 p.m.-5:00 p.m.). Compared to week 1, peak O2 uptake rose significantly during the season and was 10% and 7% higher at weeks 4 and 7, respectively. Levels of dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), cortisol, testosterone, and leptin increased significantly in response to the graded exercise tests. Testosterone levels were also changed over the course of the study. Resting testosterone levels and testosterone responses to exercise in weeks 4 and 7 were both higher than in week 1. Resting concentrations and acute increases of the other hormones were not changed over the season. It appears, therefore, that DHEA, DHEAS, cortisol, testosterone and leptin concentrations increase in response to running in adolescent female runners. Data also suggest that training and/or maturation increases resting testosterone concentrations and testosterone responses to running in adolescent female runners during a training season.

Exercise training intensity/volume affects plasma and tissue adiponectin concentrations in the male rat

The objective of the study was to determine the effects of exercise training intensity/volume on plasma total and high molecular weight (HMW) adiponectin and tissue total adiponectin concentrations. Thirty-two, eight week-old male Wistar rats (185 ± 5g) were randomly assigned to one of four groups: high intensity (HI: 34 m/min ∼%80-%85 VO(2)max), moderate intensity (MI: 28 m/min ∼%70-%75 VO(2)max), low intensity (LI: 20 m/min ∼ %50-%55 VO(2)max), and sedentary control (SED). Experimental groups completed a 12-week exercise program of treadmill running at 0° slope, 1h/day, 5 days/week. Since frequency and duration of exercise were identical among training groups, the volume of training was highest in the HI group followed by the MI and LI groups. Compared with SED animals, fasting plasma total and HMW adiponectin and adipose tissue total adiponectin concentrations were significantly higher in the HI and MI groups, but total adiponectin concentrations in liver and soleus muscle were not significantly lower than the SED rats. There were significantly lower plasma total testosterone levels in the HI group vs. SED group. Plasma total and HMW adiponectin were negatively correlated with HOMA-IR and insulin whereas total adiponectin was inversely related to TNF-α and HMW adiponectin was negatively correlated with total testosterone. Thus, data suggest there is a dose effect for exercise training intensity and accompanying volume for the adaptation of adipose tissue and circulating total and HMW adiponectin concentrations, whereas the changes of adiponectin concentrations in skeletal muscle and liver tissue may depend on the body's energy balance in the recovery period.

Plasma cell-free mitochondrial DNA declines in response to prolonged moderate aerobic exercise

Increased plasma cell‐free mitochondrial DNA (cf‐mDNA), a damage‐associated molecular pattern (DAMP) produced by cellular injury, contributes to neutrophil activation/inflammation in trauma patients and arises in cancer and autoimmunity. To further understand relationships between cf‐mDNA released by tissue injury, inflammation, and health benefits of exercise, we examined cf‐mDNA response to prolonged moderate aerobic exercise. Seven healthy moderately trained young men (age = 22.4 ± 1.2) completed a treadmill exercise trial for 90 min at 60% VO₂ max and a resting control trial. Blood was sampled immediately prior to exercise (0 min = baseline), during (+18, +54 min), immediately after (+90 min), and after recovery (R40). Plasma was analyzed for cf‐mDNA, IL‐6, and lactate. A significant difference in cf‐mDNA response was observed between exercise and control trials, with cf‐mDNA levels reduced during exercise at +54 and +90 (with or without plasma volume shift correction). Declines in cf‐mDNA were accompanied by increased lactate and followed by an increase in IL‐6, suggesting a temporal association with muscle stress and inflammatory processes. Our novel finding of cf‐mDNA decline with prolonged moderate treadmill exercise provides evidence for increased clearance from or reduced release of cf‐mDNA into the blood with prolonged exercise. These studies contrast with previous investigations involving exhaustive short‐term treadmill exercise, in which no change in cf‐mDNA levels were reported, and contribute to our understanding of differences between exercise‐ and trauma‐induced inflammation. We propose that transient declines in cf‐mDNA may induce health benefits, by reducing systemic inflammation.

Effect of estrogen on serum DHEA in younger and older women and the relationship of DHEA to adiposity and gender

This case-controlled study consisted of 2 parts. The objective of part 1 was to determine the relationship between DHEA, body mass index (BMI), and age in young males, young females, and postmenopausal (PM) females. Part 2 examined the effects of estrogen on DHEA by analyzing the relationship between DHEA and age in young females on and off oral contraceptives (OCs) and PM females on and off estrogen or hormone replacement therapy (ERT/HRT). The study was performed at the Obstetrics and Gynecology Clinic, Texas Tech Health Sciences Center-Amarillo, Exercise Physiology Laboratory at Southeastern Louisiana University, and Woman's Health Research Institute, Woman's Hospital, Baton Rouge, LA. Part 1 groups consisted of: (1) young males between the ages of 18 to 40 years; (2) normally cycling females off OCs, ages 18 to 40 years; and (3) PM females older than 40 years not receiving ERT/HRT. Part 2 groups consisted of: (1) normally cycling females on OCs, ages 18 to 40 years;, (2) normally cycling females off OCs, ages 18 to 40 years; (3) PM females 50 years or older not receiving ERT/HRT; and (4) PM females 50 years or older receiving ERT/HRT. The main outcome measure was serum DHEA concentrations. For part 1, there were significant (P <.05) inverse relationships between DHEA and age for young males; young females, off OCs; PM females, no ERT/HRT r = -.44, -.26, and -.25, respectively. There were no significant relationships between DHEA and BMI for any of the groups. DHEA concentrations were significantly higher in young males than young females even after accounting for age. For part 2, DHEA concentrations were significantly higher in young females off OCs compared with young females on OCs, and significantly higher in PM women off ERT/HRT than those on ERT\HRT. There were significant inverse relationships between DHEA and age for young females and PM females on and off ERT/HRT. From these findings, we conclude that there is an inverse relationship between DHEA and age for young males, young females off OCs, and PM females, no ERT/HRT. No relationship between BMI and DHEA was observed in these same 3 groups. These results agree with previous findings in young men, but differ from previous findings in obese young females. The data also suggest that estrogen treatment (OCs and ERT/HRT) suppresses DHEA concentrations in premenopausal and PM females, and that DHEA declines with age in PM females regardless of estrogen treatment.