Significant Effect Of Exercise Research Articles

Differences in Plantar Pressure Loading Variables Between Elliptical Exercise and Treadmill Walking

PURPOSE: To determine what differences exist in plantar pressure loading parameters between treadmill and elliptical devices. METHODS: A convenience sample of 30 asymptomatic subjects (18 females, 11 males, mean age 22 ± 2.1 and 23 ± 1.9 years of age, respectively) were recruited. After obtaining informed consent, subjects were fitted with a pair of running shoes and afforded a 5 minute training bout of treadmill walking at 3 mph followed by a 5 minute rest period. The training bout was repeated on an elliptical. A pair of pressure sensing insoles were then inserted into the running shoes and the subject commenced using either the treadmill or the elliptical, the order of which was determined randomly. Plantar pressure data were collected at a rate of 100 Hz for 30 seconds while the subjects used the devices. A 3 minute rest period was then afforded each subject before commencing the second exercise. Data Analysis: The foot was divided into 8 regions, the heel; midfoot; first, second, and lateral metatarsals; hallux; and second and lateral toes and the peak plantar pressure (PPP) and pressure time integral (PTI) determined for each step. The mean PPP and PTI of 10 steps were obtained for the feet of the subjects for each exercise and compared using a 3 factor, fixed effects ANOVA model. RESULTS: A significant effect of exercise and foot region on the mean PPP (See Table) was noted (p <.0001). Regardless of region the elliptical exhibited significantly (p <.0001) less mean PPP than the treadmill. A significant effect of region only (p <.0001) on the mean PTI was noted (See Table) with only the heel having a significantly (p <.0001) different mean PTI. CONCLUSIONS: Elliptical devices appear to generate less mean PPP and similar PTI than treadmill devices.Table 1

Weight-bearing Exercises On Bone Health In Girls And Young Women During Growth: A Meta-analysis

The risk of osteoporosis and bone fractures with advancing age is thought to be partly determined by accrual of bone mass during the growth years and in early adulthood. A number of exercise interventions have been conducted to maximize peak bone mass, yet results remain controversial. PURPOSE: To determine the effectiveness of weight-bearing exercise on bone mass in early life and identify key moderating variables influencing this process. METHODS: Articles were searched from 1992 to the present using PubMed, CINAHL, Physical Education Index, Science Direct, and ProQuest. Search terms included phrases such as "bone mass", "bone health", and "exercise." Studies featuring control groups, healthy females under the age of 30 years, and outcome measures such as areal bone mineral density (aBMD) or bone mineral content (BMC), were identified for possible inclusion in this analysis. Because an increase in BMC may not necessarily reflect greater aBMD, aBMD and BMC were analyzed separately. Comprehensive Meta-Analysis software was used to determine weighted mean effect sizes (ES) and to conduct moderator analyses. ES calculations, computed based on a comparison of change scores between control and intervention groups, accounted for the biological maturation effect. Moderator variables examined were participants' age, type of exercise, intervention duration, and bone regions of interest. RESULTS: Of 98 potentially relevant articles, 12 ES values from 9 articles and 7 ES values from 6 articles were calculated using a random-effects model for aBMD and BMC, respectively. Results showed no significant effect of exercise on aBMD (overall ES = 0.02, 95% CI = -0.11, 0.15) and BMC (overall ES = 0.001, 95%CI = -0.17, 0.17). Regardless of aBMD or BMC, analyses revealed that overall ES values were not affected by any moderator variable. CONCLUSIONS: Although constrained by the limited number of relevant research-based articles, findings from this meta-analysis suggest that factors such as nutritional intake and pubertal status may exert stronger independent effects or interact with exercise and physical activity to optimize bone health in childhood, adolescence, and early adulthood.

Exercise and NSAIDs

The purpose of this study was to determine muscle and tendon protein fractional synthesis rates (FSR) at rest and after a one-legged kicking exercise in patients with knee osteoarthritis (OA) receiving either placebo or nonsteroidal anti-inflammatory drugs (NSAIDs). Twenty patients with knee OA (50-70 yr) were enrolled. For each of the 3 days before the exercise intervention, 9 patients were administered NSAIDs (1200 mg), and 11 patients were administered placebo in a double-blinded manner. Each patient performed 60 min of one-legged kicking at 55% of workload maximum while the contralateral leg remained rested. Twenty-four hours after exercise, we determined circulating concentrations of inflammatory parameters and measured FSR of myofibrillar and sarcoplasmic protein fractions of vastus lateralis muscle and patellar tendon collagen protein by the direct incorporation method using a flooding dose of 13C/12C-proline. Circulating levels of prostaglandin F2α were lower in the NSAID group compared with the placebo group (P < 0.05). There was an overall significant effect of exercise on FSR in muscle myofibrillar (P = 0.003) and sarcoplasmic protein (P = 0.026) but not in tendon collagen protein (P = 0.52). No overall significant effect of the drug was seen on either of the tissue protein fractions (P > 0.05) or on the interaction between the drug and exercise on FSR in tendon collagen (P = 0.21), muscle myofibrillar (P = 0.68), or sarcoplasmic protein, FSR (P = 0.16). In elderly patients with knee OA, an acute bout of moderate exercise significantly increases FSR of muscle myofibrillar and sarcoplasmic protein, but not tendon collagen, 24 h after exercise. NSAID administration in patients with knee OA reduced the level of circulating prostaglandin F2α but did not diminish the exercise-induced response of muscle contractile protein FSR. However, we cannot exclude that a minor inhibition of muscle sarcoplasmic proteins may have been present with NSAID treatment. This study suggests that muscle hypertrophy after long-term training is not influenced by NSAIDs.

Targeted exercise against osteoporosis: A systematic review and meta-analysis for optimising bone strength throughout life.

BackgroundExercise is widely recommended to reduce osteoporosis, falls and related fragility fractures, but its effect on whole bone strength has remained inconclusive. The primary purpose of this systematic review and meta-analysis was to evaluate the effects of long-term supervised exercise (≥6 months) on estimates of lower-extremity bone strength from childhood to older age.MethodsWe searched four databases (PubMed, Sport Discus, Physical Education Index, and Embase) up to October 2009 and included 10 randomised controlled trials (RCTs) that assessed the effects of exercise training on whole bone strength. We analysed the results by age groups (childhood, adolescence, and young and older adulthood) and compared the changes to habitually active or sedentary controls. To calculate standardized mean differences (SMD; effect size), we used the follow-up values of bone strength measures adjusted for baseline bone values. An inverse variance-weighted random-effects model was used to pool the results across studies.ResultsOur quality analysis revealed that exercise regimens were heterogeneous; some trials were short in duration and small in sample size, and the weekly training doses varied considerably between trials. We found a small and significant exercise effect among pre- and early pubertal boys [SMD, effect size, 0.17 (95% CI, 0.02-0.32)], but not among pubertal girls [-0.01 (-0.18 to 0.17)], adolescent boys [0.10 (-0.75 to 0.95)], adolescent girls [0.21 (-0.53 to 0.97)], premenopausal women [0.00 (-0.43 to 0.44)] or postmenopausal women [0.00 (-0.15 to 0.15)]. Evidence based on per-protocol analyses of individual trials in children and adolescents indicated that programmes incorporating regular weight-bearing exercise can result in 1% to8% improvements in bone strength at the loaded skeletal sites. In premenopausal women with high exercise compliance, improvements ranging from 0.5% to 2.5% have been reported.ConclusionsThe findings from our meta-analysis of RCTs indicate that exercise can significantly enhance bone strength at loaded sites in children but not in adults. Since few RCTs were conducted to investigate exercise effects on bone strength, there is still a need for further well-designed, long-term RCTs with adequate sample sizes to quantify the effects of exercise on whole bone strength and its structural determinants throughout life.

The Effects Of Prior Exercise And Protein Co-ingestion On The Glycemic Response To Carbohydrate.

PURPOSE: The purpose of this study was to investigate the effects of prior exercise and protein co-ingestion on the glycemic response to the ingestion of carbohydrate. METHODS: 21 healthy subjects (13 men and 8 women; 22±3.82 yrs 174±6.7 cm, body weight 69±11.5 kg; values are mean±SD) participated in 4 trials in random order after an overnight fast. These included: 1) glucose ingestion at rest (RG), 2) glucose and protein ingestion at rest (RGP), 3) glucose ingestion after exercise (EG), and 4) glucose and protein ingestion after exercise (EGP). Exercise consisted of 45 minutes of cycling at 60% of subjects' age-predicted maximum heart rate. Test drinks contained 50 g glucose or 50 g glucose with 20 g whey protein. Venous blood samples were taken 0, 15, 30, 45, 60, 75, 90, 105 and 120 minutes after drink consumption. Blood plasma was subsequently analysed for glucose and insulin. RESULTS: Plasma glucose concentration was significantly lower in RGP compared to RG at 30, 45, 60 and 75 minutes and in EGP compared to EG at 30, 45 and 60 minutes (p<0.05). Plasma insulin area under the curve was significantly higher in RGP than RG (p<0.05). No significant effect of exercise was seen on glycemic or insulinemic responses. CONCLUSION: Co-ingestion of protein with carbohydrate reduces the glycemic response and increases insulinemic response in healthy subjects, while prior low-moderate intensity exercise appears to have minimal effect.

Influence of Acute Exercise on Serum Homocysteine in Horse

The effect of acute exercise on serum homocysteine (sHCy) concentration was examined in 10 horses; five Sella Italiana and five Thoroughbreds. All horses underwent standard training before the study (show jumping for Sella Italiana horses and gallop racing for Thoroughbreds). For the study, blood samples were taken at rest, immediately after exercise, and during a recovery period (30 and 60 minutes after exercise) by external jugular venipuncture. sHCy values were determined by high-performance liquid chromatography. Heart rate and blood lactate were monitored to quantify the workloads. In show jumpers, there was a significant effect of sampling time on sHCy ( P < .01), which increased significantly after exercise as compared with at rest. In Thoroughbreds, no statistically significant differences were observed in sHCy over time (F (3,12) = 0.89, P = .05). The baseline values of sHcy were higher in Thoroughbreds than in show jumpers ( P < .0002). We infer that physical activity causes biochemical changes that can influence the metabolic pathway of homocysteine in show jumpers, whereas the absence of a significant effect of exercise in Thoroughbreds may reflect an adaptive response of the enzymatic antioxidant defense system.

Biological Mechanisms of Physical Activity in Preventing Cognitive Decline

In order to guarantee better conditions for competition, the nervous system has developed not only mechanisms controlling muscle effectors, but also retrograde systems that, starting from peripheral structures, may influence brain functions. Under such perspective, physical activity could play an important role in influencing cognitive brain functions including learning and memory. The results of epidemiological studies (cross-sectional, prospective and retrospective) support a positive relationship between cognition and physical activities. Recent meta-analysis confirmed a significant effect of exercise on cognitive functions. However, the biological mechanisms that underlie such beneficial effects are still to be completely elucidated. They include supramolecular mechanisms (e.g. neurogenesis, synaptogenesis, and angiogenesis) which, in turn, are controlled by molecular mechanisms, such as BDNF, IGF-1, hormone and second messengers.

Optimum frequency of exercise for bone health: Randomised controlled trial of a high-impact unilateral intervention

Introduction Exercise can increase bone strength, but to be effective in reducing fracture risk, exercise must be feasible enough to be adopted into daily life and influence potentially vulnerable skeletal sites such as the superolateral cortex of the femoral neck, where thinning is associated with increased fracture risk. Brief, high-impact exercise increases femoral neck bone density but the optimal frequency of such exercise and the location of bone accrual is unknown. This study thus examined (1) the effectiveness of different weekly frequencies of exercise on femoral neck BMD and (2) whether BMD change differed between hip sites using a high-impact, unilateral intervention. Methods Healthy premenopausal women were randomly assigned to exercise 0, 2, 4, or 7 days/week for 6 months. The exercise intervention incorporated 50 multidirectional hops on one randomly selected leg. BMD was measured by DXA at baseline and after 6 months of exercise. Changes in the exercise leg were compared between groups using ANCOVA, with change in the control leg and baseline BMD as covariates. RM-MANOVA was conducted to determine whether bone changes from exercise differed between hip sites. Results 61 women (age 33.6 ± 11.1 years) completed the intervention. Compliance amongst exercisers was 86.7 ± 10.6%. Peak ground reaction forces during exercise increased from 2.5 to 2.8 times body weight. The change in femoral neck BMD in the exercise limb (adjusted for change in the control limb and baseline BMD) differed between groups ( p = 0.015), being − 0.3% (− 1.2 to 0.6), 0.0% (− 1.0 to 1.0), 0.9% (− 0.1 to 2.0) and 1.8% (0.8 to 2.8) in those exercising 0, 2, 4 and 7 days per week, respectively. When BMD changes at upper neck, lower neck and trochanter were compared using RM-MANOVA, a significant exercise effect was observed ( p = 0.048), but this did not differ significantly between sites ( p = 0.439) despite greatest mean increases at the upper femoral neck. Conclusions Brief, daily hopping exercises increased femoral neck BMD in premenopausal women but less frequent exercise was not effective. Brief high-impact exercise may have a role in reducing hip fragility, but may need to be performed frequently for optimal response.

Influence of exercise and joint topography on depth‐related spatial distribution of proteoglycan and collagen content in immature equine articular cartilage

There is ample evidence on topographical heterogeneity of the principal biochemical components of articular cartilage over the surface of the joint and the influence of loading thereon, but no information on depth-related zonal variation in horses. To study depth-related zonal variation in proteoglycan (PG) and collagen content in equine articular cartilage. Two techniques (safranin-O densitometry and Fourier transform infrared spectroscopy) were applied to sections of articular cartilage from the proximal phalangeal bone of the metacarpophalangeal joint of 18-month-old Thoroughbreds that had been raised at pasture from age 0-18 months without (PASTEX) and with (CONDEX) additional exercise. Two sites were investigated: site 1 at the joint margin that is unloaded at rest or at slow gaits, but subjected to high-intensity loading during athletic activity; and site 2, a continuously, but less intensively, loaded site in the centre of the joint. Proteoglycan values increased from the surface to the deep layers of the cartilage, collagen content showed a reverse pattern. PG content was significantly higher at site 2 in both PASTEX and CONDEX animals without an effect of exercise. In the PASTEX animals collagen content was significantly higher at site 1, but in the CONDEX group the situation was reversed, due to a significant exercise effect on site 1, leading to a reduced collagen content. Collagen and PG content gradients agree with findings in other species. The observations on PG levels suggest that the exercise level was not strenuous. The collagen results in the PASTEX group confirmed earlier findings, the lower levels at site 1 in the CONDEX group being possibly due to an advancement of the physiological maturation process of collagen remodelling. This study confirms earlier observations that even moderate variations in exercise level in early age may have significant effects on the collagen network of articular cartilage.

Knowledge of carbohydrate consumption does not alter natural killer cell activity following an acute bout of high-intensity aerobic exercise

Carbohydrate consumption during strenuous aerobic exercise reportedly minimizes post-exercise suppression of the innate immune system. One of the most common measurements of innate immunity is natural killer cell activity (NKCA). It is not known whether actual carbohydrate consumption or merely the knowledge of carbohydrate consumption mediates alteration in NKCA. The purpose of the present investigation was to determine if knowledge of carbohydrate beverage could result in alteration of RPE and NKCA, independent of actual carbohydrate intake. We recruited 11 male and female endurance athletes and randomly assigned them to either a correct or false knowledge of carbohydrate intake, such that in the false group, subjects were informed that they were receiving the carbohydrate beverage (CHO), but actually received a placebo (PLA) beverage. CHO and PLA beverages were matched to be similar in taste and appearance. Subjects completed 60 min of cycle ergometry (74% of VO2 peak). Venous blood samples were collected before (PRE), immediately after (POST), and 2 h after (2H) exercise and used to determine plasma glucose concentration, leukocyte total and differential counts, and NKCA. Data were statistically analyzed using a 3-factor analysis of variance (ANOVA) (p < 0.05). We did not find a significant effect of knowledge of drink type on leukocyte count, leukocyte differential, or NKCA. Drink type did not significantly alter leukocyte total, differential counts, or NKCA. There was a significant effect of exercise on NKCA. Knowledge of drink type does not alter innate immunity following exercise as assessed by leukocyte counts and NKCA.

Knowledge of carbohydrate consumption does not alter exercise‐induced lymphocyte apoptosis following an acute bout of high‐intensity aerobic exercise

Carbohydrate consumption during strenuous aerobic exercise has been reported to reduce the amount of lymphocyte cell death compared to placebo. It is not known whether actual carbohydrate consumption or merely the knowledge of carbohydrate consumption mediates this alteration. The purpose of this investigation was to determine if knowledge of carbohydrate beverage could result in an alteration of apoptotic lymphocytes, independent of actual carbohydrate intake. Endurance trained males and females (N = 10) were randomly assigned to either a correct or false knowledge of carbohydrate intake. For instance in the false group, subjects were informed that they were receiving the carbohydrate beverage, but actually received the placebo beverage. Participants completed a 60‐min ride on a cycle ergometer at 80% VO2peak. Venous blood samples were collected at rest (PRE) and immediately after exercise (POST), and used to determine plasma glucose concentration and lymphocyte apoptosis. We did not find a significant effect of knowledge of drink type on lymphocyte cell death (P = 0.43). There was a significant effect of exercise on lymphocyte apoptosis (PRE = 6.3±3%, POST = 11.6±3%, P&lt;0.01). Knowledge of drink type does not appear to alter immunity in terms of lymphocyte cell death following exercise.

Effect of 6 months of exercise and isoflavone supplementation on clinical cardiovascular risk factors in obese postmenopausal women

To investigate whether 6 months of exercise combined with isoflavone supplementation could improve clinical risk factors that predispose to cardiovascular disease in obese postmenopausal women. This was a randomized, double-blind, controlled trial in which 50 healthy obese postmenopausal women were divided into two groups and assigned to isoflavone supplementation (n=25) or a placebo (n=25) for 1 year. For the last 6 months, both groups participated in an exercise program (three times per week), at the end of which cardiovascular disease risk factors were compared between groups. Body composition (using dual-energy x-ray absorptiometry), metabolic profile (blood lipids, fasting insulin, fasting glucose, sex hormone-binding globulin, C-reactive protein) were determined at baseline and at 6 and 12 months. We observed a significant effect of exercise and isoflavone supplementation on body weight, total and abdominal fat mass (kilograms and percentage), body mass index, appendicular fat-free mass, fat-free mass/fat mass ratio, and sex hormone-binding globulin, but not with exercise alone. No difference was observed for other biochemical characteristics, although the quantitative insulin sensitivity check index increased equally in both groups. Conversely, although not significant, we observed a tendency for a treatment effect on body mass index (P=0.07) and on absolute (kilograms) (P=0.07) and percentage of (P=0.053) abdominal fat mass, whereas no effect of treatment was found for other variables using the Mann-Whitney test. Compared to an aerobic exercise program alone, 70 mg/day of isoflavones combined with exercise may promote significant improvements in body composition parameters that are known to influence cardiovascular disease risk in postmenopausal women.

Effects of exercise on gut peptides, energy intake and appetite

This study investigated the acute effects of exercise on the postprandial levels of appetite-related hormones and metabolites, energy intake (EI) and subjective measures of appetite. Ghrelin, polypeptide YY (PYY), glucagon-like peptide-1 (GLP-1) and pancreatic polypeptide (PP) were measured in the fasting state and postprandially in 12 healthy, normal-weight volunteers (six males and six females) using a randomised crossover design. One hour after a standardised breakfast, subjects either cycled for 60 min at 65% of their maximal heart rate or rested. Subjective appetite was assessed throughout the study using visual analogue scales and subsequent EI at a buffet meal was measured at the end (3-h post-breakfast and 1-h post-exercise). Exercise significantly increased mean PYY, GLP-1 and PP levels, and this effect was maintained during the post-exercise period for GLP-1 and PP. No significant effect of exercise was observed on postprandial levels of ghrelin. During the exercise period, hunger scores were significantly decreased; however, this effect disappeared in the post-exercise period. Exercise significantly increased subsequent absolute EI, but produced a significant decrease in relative EI after accounting for the energy expended during exercise. Hunger scores and PYY, GLP-1 and PP levels showed an inverse temporal pattern during the 1-h exercise/control intervention. In conclusion, acute exercise, of moderate intensity, temporarily decreased hunger sensations and was able to produce a short-term negative energy balance. This impact on appetite and subsequent energy homeostasis was not explained by changes in postprandial levels of ghrelin; however, 'exercise-induced anorexia' may potentially be linked to increased PYY, GLP-1 and PP levels.

Exercise and bone mineral density at the femoral neck in postmenopausal women: A meta-analysis of controlled clinical trials with individual patient data

We conducted a meta-analysis using individual patient data to examine the efficacy of exercise for improving bone mineral density at the femoral neck in postmenopausal women. Ten controlled clinical trials that included 595 subjects (aged 42-92 years) met our criteria for inclusion. Changes in femoral neck bone mineral density were examined by 2-way analysis of variance tests with repeated measures on 1 factor. Across all designs and categories, there was an increase in bone mineral density of 0.73% +/- 5.52% and 0.45% +/- 6.78%, respectively, in the exercise and control subjects. However, comparison of initial and final bone mineral density values between exercise and control subjects revealed no statistically significant effect of exercise on femoral neck bone mineral density (P > .05). Collectively, the exercise protocols that were used in this individual patient data meta-analysis do not improve femoral neck bone mineral density in postmenopausal women.

Serum Lipoproteins in Overweight/Obese Postmenopausal Women

This analysis was conducted to study the effect of a 1-yr moderate-intensity aerobic exercise program on serum lipoproteins among overweight/obese postmenopausal women. We randomized 173 sedentary (VO2max = 20.2 mL.kg(-1).min(-1)), overweight/obese women (body mass index (BMI) 25.0-42.0 kg.m(-2) or body fat > 33% if BMI 24.0-25.0) aged 50-75 yr, not using hormone therapy, living in the Seattle area, to an exercise intervention or stretching control group. The exercise intervention included facility and home-based exercise (45 min, 5 d.wk(-1) of moderate-intensity sports or recreational exercise). Total cholesterol (TC), triglycerides, and high-density lipoprotein (HDL) were determined by chemical assay; low-density lipoprotein (LDL) was then calculated. Of the 173 women, 170 (98.3%) completed the study with exercisers averaging 176 (SD 91) min.wk(-1) of moderate- to vigorous-intensity (60%-75% HRmax) exercise, expending approximately 3828 kJ.wk(-1) (SD 2053). Exercisers, compared with stretchers, significantly increased their VO2max (+11%, P<0.001) and lost more body weight (-1.4 kg, P < 0.05), DEXA-% total body fat (-1.0, P < 0.005), L4-5 computed tomography intraabdominal fat (-8.6 cm2, P < 0.05) and subcutaneous abdominal fat (-28.8 cm2, P < 0.005) after 12 months. Mean (SD) baseline lipoprotein levels for TC, LDL, HDL, and triglycerides were 231 (39), 152 (39), 52 (12), and 135 (65) mg.dL(-1), respectively. We observed no significant change in serum lipoprotein levels among exercisers compared with stretchers at either 3 or 12 months postrandomization. We did not observe a statistically significant effect of exercise on serum lipoproteins in subgroups that changed their intraabdominal and subcutaneous fat, percent total body fat, or VO2max the most, or that adhered to the exercise regimen the most over 1 yr. It appears that a year long moderate-intensity exercise program alone does not significantly alter serum lipoprotein levels among overweight/obese postmenopausal women.

Lipid metabolism in young men after acute resistance exercise at two different intensities

The aim of this study was to examine the effects of different resistance training loads on blood lipids. Six healthy, untrained male volunteers performed three protocols: control (no exercise), high intensity (HI) and low intensity (LI) exercise seven days apart. Each protocol comprised eight exercises. The HI protocol used a 10-repetition maximum (RM) load and 10 repetitions. In the LI protocol, the load was halved and repetitions doubled. The volume of work performed in the two exercise protocols was identical. Blood samples were collected before, immediately after, and 15 min after each protocol and analysed for total, high density (HDL-C), low density cholesterol and triglyceride. The only significant effect of exercise was to acutely increase HDL-C in the immediate post exercise sample compared with the control. There was no significant effect on any lipid fraction resulting from the LI protocol compared with the control. The results of this study suggest that intensity alone has an effect in determining the HDL-C response to acute resistance exercise.

Polyethylene glycol but not mifepristone prevents intestinal lymphocyte loss following treadmill exercise in mice

Circulating lymphocyte numbers decrease following intense physical activity, possibly due to exercise-induced apoptosis. Increased reactive oxygen species (ROS) and glucocorticoids (GC) following exercise contribute to lymphocyte apoptosis. Intestinal lymphocyte (IL) numbers also decrease following exercise. The purpose of this study was to determine the contribution of GC to exercise-induced IL loss. Female C57BL/6 mice (n = 178) were randomized to five drug conditions: (1) single injection of the glucocorticoid receptor antagonist mifepristone (MIF) solubilized in polyethylene glycol (PEG); (2) three injections of MIF (repeated MIF) PEG; (3) single injection of PEG (PEG); (4) three injections of PEG (repeated PEG); or (5) repeated injections of saline (SAL). Within each drug group mice were further randomized to exercise conditions: (1) control condition (non-exercised); (2) treadmill running with sacrifice immediately following the exercise; or (3) treadmill running with sacrifice 24 h after completion of the exercise. There was a significant exercise effect, across all T lymphocyte subsets, in SAL (P < 0.01), PEG (P < 0.01) and MIF (P < 0.01) treated mice but not in mice given repeated PEG or repeated MIF exposure. The exercise effect was due to reduced IL numbers 24 h post-exercise compared with non-exercised controls. These results suggest that GC are not directly responsible for IL cell loss following exercise. Repeated exposure to PEG may confer protection in the gastrointestinal tract from exercise-induced lymphocyte depletion. Because PEG inhibits ROS generation in experimental cell injury, the mechanisms for IL loss after exercise may involve oxidative stress.

IGF-I System Responses Following Differing Volumes of Acute Resistance and Aerobic Exercise

1663 The literature is equivocal regarding how acute exercise influences IGF-I concentrations with equal numbers of studies reporting increases, decreases, or no changes. We have previously reported that high volume, resistance exercise had no effect on overnight IGF-I, but altered IGF-I regulatory binding proteins (Nindl, JAP, 2001) and suggested that IGFBPs may be sensitive biomarkers of exercise-induced stress. PURPOSE: To examine the hypothesis that IGFBPs, rather than IGF-I itself, would prove to be more responsive to acute exercise stress in a dose-dependent fashion. METHODS: 8 men (24 ± 5 yr, 87 ± 9 kg, 182 ± 6 cm, 21 ± 5 %BF) had blood drawn every 4 hrs post-exercise for 24 hrs and assayed for IGF-I, IGFBPs 1 and 3 and the acid labile subunit (ALS) on 5 occasions, each separated by a month and counterbalanced: control (C; no exercise), moderate volume resistance exercise (MR; 25, 5–10 RM sets), high volume resistance exercise (HR; 50, 5–10 RM sets), moderate volume aerobic exercise (MA; 3, 15-minute cycling bouts @ ∼70 VO2 max) high volume aerobic exercise (HA; 6, 15-minute cycling bouts @ ∼70% VO2 max). Energy requirements were determined from resting metabolic rate, age and a physical activity factor. Dietary control was implemented by providing all meals the day of and the day after the exercise bouts. A two-way ANOVA with repeated measures (p < 0.05) was used for statistical analysis. RESULTS: Significant exercise effects were observed for IGFBP-1 (ng/ml) (C: 14.0 ± 2.7 moderate volume exercise [35 ± 7 ng/ml]). There were no exercise effects for total IGF-I (ng/ml) (C: 346 ± 38; MR: 336 ± 28; HR: 303 ± 40; MA: 327 ± 41; HA: 347 ± 52), IGFBP-3 (ng/ml) (C: 4245 ± 215; MR: 4114 ± 207; HR: 4097 ± 297; MA: 4191 ± 262; HA: 4167 ± 239) or ALS (μg/ml) (C: 14.0 ± 1.2; MR: 15.8 ± 1.5; HR: 15.0 ± 1.6; MA: 15.5 ± 1.3; HA: 15.3 ± 1.2). CONCLUSION: For the circulating IGF-I system components measured, only IGFBP-1 appears to be a sensitive biomarker capable of assessing the physiological strain of acute physical exercise. These data are suggestive that exercise affects IGF-I partitioning among binary molecular complexes in a dose-dependent manner.

IGF-I System Responses Following Differing Volumes of Acute Resistance and Aerobic Exercise

1663 The literature is equivocal regarding how acute exercise influences IGF-I concentrations with equal numbers of studies reporting increases, decreases, or no changes. We have previously reported that high volume, resistance exercise had no effect on overnight IGF-I, but altered IGF-I regulatory binding proteins (Nindl, JAP, 2001) and suggested that IGFBPs may be sensitive biomarkers of exercise-induced stress. PURPOSE: To examine the hypothesis that IGFBPs, rather than IGF-I itself, would prove to be more responsive to acute exercise stress in a dose-dependent fashion. METHODS: 8 men (24 ± 5 yr, 87 ± 9 kg, 182 ± 6 cm, 21 ± 5 %BF) had blood drawn every 4 hrs post-exercise for 24 hrs and assayed for IGF-I, IGFBPs 1 and 3 and the acid labile subunit (ALS) on 5 occasions, each separated by a month and counterbalanced: control (C; no exercise), moderate volume resistance exercise (MR; 25, 5–10 RM sets), high volume resistance exercise (HR; 50, 5–10 RM sets), moderate volume aerobic exercise (MA; 3, 15-minute cycling bouts @ ∼70 VO2 max) high volume aerobic exercise (HA; 6, 15-minute cycling bouts @ ∼70% VO2 max). Energy requirements were determined from resting metabolic rate, age and a physical activity factor. Dietary control was implemented by providing all meals the day of and the day after the exercise bouts. A two-way ANOVA with repeated measures (p < 0.05) was used for statistical analysis. RESULTS: Significant exercise effects were observed for IGFBP-1 (ng/ml) (C: 14.0 ± 2.7 moderate volume exercise [35 ± 7 ng/ml]). There were no exercise effects for total IGF-I (ng/ml) (C: 346 ± 38; MR: 336 ± 28; HR: 303 ± 40; MA: 327 ± 41; HA: 347 ± 52), IGFBP-3 (ng/ml) (C: 4245 ± 215; MR: 4114 ± 207; HR: 4097 ± 297; MA: 4191 ± 262; HA: 4167 ± 239) or ALS (μg/ml) (C: 14.0 ± 1.2; MR: 15.8 ± 1.5; HR: 15.0 ± 1.6; MA: 15.5 ± 1.3; HA: 15.3 ± 1.2). CONCLUSION: For the circulating IGF-I system components measured, only IGFBP-1 appears to be a sensitive biomarker capable of assessing the physiological strain of acute physical exercise. These data are suggestive that exercise affects IGF-I partitioning among binary molecular complexes in a dose-dependent manner.

The significance of high bone density in children

The significance of high bone density in children