Beneficial metabolic adaptations due to endurance exercise training in the fasted state

Training with limited carbohydrate availability can stimulate adaptations in muscle cells to facilitate energy production via fat oxidation. Here we investigated the effect of consistent training in the fasted state, vs. training in the fed state, on muscle metabolism and substrate selection during fasted exercise. Twenty young male volunteers participated in a 6-wk endurance training program (1-1.5 h cycling at ～70% Vo(?max), 4 days/wk) while receiving isocaloric carbohydrate-rich diets. Half of the subjects trained in the fasted state (F; n = 10), while the others ingested ample carbohydrates before (～160 g) and during (1 g·kg body wt?1·h?1) the training sessions (CHO; n = 10). The training similarly increased Vo(?max) (+9%) and performance in a 60-min simulated time trial (+8%) in both groups (P < 0.01). Metabolic measurements were made during a 2-h constant-load exercise bout in the fasted state at ～65% pretraining Vo(?max). In F, exercise-induced intramyocellular lipid (IMCL) breakdown was enhanced in type I fibers (P < 0.05) and tended to be increased in type IIa fibers (P = 0.07). Training did not affect IMCL breakdown in CHO. In addition, F (+21%) increased the exercise intensity corresponding to the maximal rate of fat oxidation more than did CHO (+6%) (P < 0.05). Furthermore, maximal citrate synthase (+47%) and β-hydroxyacyl coenzyme A dehydrogenase (+34%) activity was significantly upregulated in F (P < 0.05) but not in CHO. Also, only F prevented the development exercise-induced drop in blood glucose concentration (P < 0.05). In conclusion, F is more effective than CHO to increase muscular oxidative capacity and at the same time enhances exercise-induced net IMCL degradation. In addition, F but not CHO prevented drop of blood glucose concentration during fasting exercise.     

Role of submaximal exercise in promoting creatine and glycogen accumulation in human skeletal muscle.

We examined the effect of glycogen-depleting exercise on subsequent muscle total creatine (TCr) accumulation and glycogen resynthesis during postexercise periods when the diet was supplemented with carbohydrate (CHO) or creatine (Cr) + CHO. Fourteen subjects performed one-legged cycling exercise to exhaustion. Muscle biopsies were taken from the exhausted (Ex) and nonexhausted (Nex) limbs after exercise and after 6 h and 5 days of recovery, during which CHO (CHO group, n = 7) or Cr + CHO (Cr+CHO group, n = 7) supplements were ingested. Muscle TCr concentration ([TCr]) was unchanged in both groups 6 h after supplementation commenced but had increased in the Ex (P < 0.001) and Nex limbs (P < 0.05) of the Cr+CHO group after 5 days. Greater TCr accumulation was achieved in the Ex limbs (P < 0.01) of this group. Glycogen was increased above nonexercised concentrations in the Ex limbs of both groups after 5 days, with the concentration being greater in the Cr+CHO group (P = 0.06). Thus a single bout of exercise enhanced muscle Cr accumulation, and this effect was restricted to the exercised muscle. However, exercise also diminished CHO-mediated insulin release, which may have attenuated insulin-mediated muscle Cr accumulation. Ingesting Cr with CHO also augmented glycogen supercompensation in the exercised muscle.     

Chronic administration of therapeutic levels of clenbuterol acts as a repartitioning agent.

The purpose of this study was to examine the effect of therapeutic levels of clenbuterol, with and without exercise training, on body composition. Twenty-three unfit Standardbred mares were divided into four experimental groups: clenbuterol (2.4 microg/kg body wt twice daily) plus exercise (ClenEx; 20 min at 50% maximal oxygen consumption 3 days/wk; n = 6), clenbuterol only (Clen; n = 6), exercise only (Ex; n = 5), and control (Con; n = 6). Rump fat thickness was measured at 2-wk intervals by using B-mode ultrasound, and percent body fat (%fat) was calculated by using previously published methods. For Ex, body fat decreased (P < 0.05) at week 4 (-9.3%), %fat at week 6 (-6.9%), and fat-free mass (FFM) increased (P < 0.05) at week 8 (+3.2%). On the other hand, Clen had significant changes in %fat (-15.4%), fat mass (-14.7%), and FFM (+4.3%) at week 2. ClenEx had significant decreases in %fat (-17.6%) and fat mass (-19.5%) at week 2, which was similar to Clen; however, this group had a different FFM response, which significantly increased (+4.4%) at week 6. Con showed no changes (P > 0.05) in any variable at any time. These results suggest that exercise training and clenbuterol have additive effects with respect to %fat and fat mass but antagonistic effects in terms of FFM. Furthermore, chronic clenbuterol administration causes significant repartitioning in the horse, even when administered in therapeutic doses.     

Exercise training enhances leg vasodilatory capacity of 65-yr-old men and women

To determine whether extremity vasodilatory capacity may be augmented in older persons by endurance exercise training, lower leg blood flow and conductance were characterized plethysmographically at rest and during maximal hyperemia in 9 men and 10 women aged 64 +/- 3 (SD) yr before and after 31 +/- 6 wk of walking and jogging at 70-90% of maximal oxygen uptake for 45 min 3-5 days/wk. Maximal oxygen uptake expressed as milliliters per kilogram per minute improved 25% in men and 21% in women (P less than 0.01). Maximal leg blood flow and conductance increased in all nine men by an average of 39 +/- 33 (P less than 0.001) and 42 +/- 44% (P less than 0.004), respectively. Results were more variable in women and achieved unequivocal statistical significance only for maximal blood flow (+33 +/- 54% for blood flow and +29 +/- 55% for conductance; P less than 0.02 and P = 0.05, respectively). Body weight and skinfold adiposity declined in both sexes (P less than 0.05). Enhancement of vasodilatory capacity was related to weight loss in men and adipose tissue loss in women (r = 0.61 and 0.51, respectively; P less than 0.05). There were no significant changes in exercise capacity, body weight, or maximal blood flow in four male and three female controls aged 66 +/- 4 yr. Thus adaptability of the lower limb circulation to endurance exercise training is retained to at least age 65 yr.     

Creatine supplementation increases muscle total creatine but not maximal intermittent exercise performance.

This study investigated creatine supplementation (CrS) effects on muscle total creatine (TCr), creatine phosphate (CrP), and intermittent sprinting performance by using a design incorporating the time course of the initial increase and subsequent washout period of muscle TCr. Two groups of seven volunteers ingested either creatine [Cr; 6 x (5 g Cr-H(2)O + 5 g dextrose)/day)] or a placebo (6 x 5 g dextrose/day) over 5 days. Five 10-s maximal cycle ergometer sprints with rest intervals of 180, 50, 20, and 20 s and a resting vastus lateralis biopsy were conducted before and 0, 2, and 4 wk after placebo or CrS. Resting muscle TCr, CrP, and Cr were unchanged after the placebo but were increased (P < 0.05) at 0 [by 22.9 +/- 4.2, 8.9 +/- 1.9, and 14.0 +/- 3.3 (SE) mmol/kg dry mass, respectively] and 2 but not 4 wk after CrS. An apparent placebo main effect of increased peak power and cumulative work was found after placebo and CrS, but no treatment (CrS) main effect was found on either variable. Thus, despite the rise and washout of muscle TCr and CrP, maximal intermittent sprinting performance was unchanged by CrS.     

Plyometric training effects on physical fitness and muscle damage in high school baseball players

[Purpose]The objective of this study was to investigate the effects of plyometric training on physical fitness and muscle damage in high school baseball players.[Methods]The participants in the study included 21 high school baseball players who are healthy and well-training. The participants were randomly allocated to the plyometric training (n=11) and control (n=10) groups. The plyometric training was applied 3 times a week for a total of 8 weeks and the control group took part in only regular baseball skills training without plyometric training. For physical fitness, measures included maximal strength (left and right hand-grip strength), muscle endurance (sit-up), agility (side-step), power (standing long jump), and balance (left and right Rhomberg test). For muscle damage, creatine kinase (CK) and lactate dehydrogenase (LDH) levels were measured.[Results]The results showed a significant interaction effect between time and groups in left hand-grip strength (P = 0.022), side-step (P = 0.004), and standing long jump (P < 0.001) after the 8-week plyometric training, with greater improvement in the plyometric training group than the control group. On the other hand, there was no significant interaction effect between time and groups in right hand-grip strength, situp, left and right Rhomberg test, CK level, and LDH level (P > 0.05).[Conclusion]In conclusion, 8-week plyometric training had a positive effect on improving physical fitness, such as maximal strength, agility, and power, in high school baseball players without causing additional muscle damage.     

Aerobic exercise training conserves insulin sensitivity for 1 yr following weight loss in overweight women

The objectives of this study were to 1) identify the independent effects of exercise (aerobic or resistance training) and weight loss on whole body insulin sensitivity and 2) determine if aerobic or resistance training would be more successful for maintaining improved whole body insulin sensitivity 1 yr following weight loss. Subjects were 97 healthy, premenopausal women, body mass index (BMI) 27-30 kg/m(2). Following randomized assignment to one of three groups, diet only, diet + aerobic, or diet + resistance training until a BMI <25 kg/m(2) was achieved, body composition, fat distribution, and whole body insulin sensitivity were determined at baseline, in the weight reduced state, and at 1-yr follow up. The whole body insulin sensitivity index (S(I)) was determined using a frequently sampled intravenous glucose tolerance test. Results of repeated-measures ANOVA indicated a significant improvement in S(I) following weight loss. However, there were no group or group×time interactions. At 1-yr follow up, there were no significant time or group interactions for S(I;) however, there was a significant group×time interaction for S(I). Post hoc analysis revealed that women in the aerobic training group showed a significant increased S(I) from weight reduced to 1-yr follow up (P < 0.05), which was independent of intra-abdominal adipose tissue and %fat. No significant differences in S(I) from weight reduced to 1-yr follow up were observed for diet only or diet + resistance groups. Additionally, multiple linear regression analysis revealed that change in whole body insulin sensitivity from baseline to 1-yr follow up was independently associated with the change in Vo(2max) from baseline to 1-yr follow up (P < 0.05). These results suggest that long-term aerobic exercise training may conserve improvements in S(I) following weight loss and that maintaining cardiovascular fitness following weight loss may be important for maintaining improvements in S(I).     

Effects of a 6-mo endurance-training program on venous compliance and maximal lower body negative pressure in older men and women.

Aging and chronic exercise training influence leg venous compliance. Venous compliance affects responses to an orthostatic stress. The extent to which exercise training in a previously sedentary older population will affect venous compliance and tolerance to the simulated orthostatic stress of maximal lower body negative pressure (LBNP) is unknown. The purpose of this investigation is to determine the influence of a 6-mo endurance-training program on calf venous compliance and responses and tolerance to maximal LBNP in older men and women. Twenty participants (exercise group: n = 10, 5 men, 5 women; control group: n = 10, 6 men, 4 women; all >60 yr) underwent graded LBNP to presyncope or 4 min at -100 mmHg before and after a 6-mo endurance-training program. Utilizing venous occlusion plethysmography, calf venous compliance was determined in both groups using the first derivative of the pressure-volume relation during cuff pressure reduction before training, at 3 mo, and at the end of the training program. The exercise group improved their fitness with the 6-mo endurance-training program, whereas the control group did not change (14 +/- 3 vs. <1 +/- 2%; P < 0.05). LBNP tolerance did not differ between groups or across trials (P = 0.47). Venous compliance was not different between groups or trials, either initially or after 3 mo of endurance training, but tended to be greater in the exercise group after 6 mo of training (P = 0.08). These data suggest that a 6-mo endurance-training program may improve venous compliance without affecting tolerance to maximal LBNP in older participants.     

Endurance training amplifies the pulsatile release of growth hormone: effects of training intensity.

The effects of intensity of run training on the pulsatile release of growth hormone (GH) were investigated in 21 eumenorrheic untrained women. The O2 consumption (VO2) at the lactate threshold (LT); fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM; peak VO2; maximal VO2; body composition; and pulsatile release of GH were measured. Subjects in both the at-lactate threshold (/LT, n = 9) and above-lactate threshold (greater than LT, n = 7) training groups increased VO2 at LT and FBLC of 2.0, 2.5, and 4.0 mM and VO2max after 1 yr of run training. However, the increase observed in the greater than LT group was greater than that in the /LT group (P less than 0.05). No change was observed for the control group (n = 5). No among- or within-group differences were observed for body weight, although trends for reductions in percent body fat (P less than 0.06) and fat weight (P less than 0.15) were observed in the greater than LT group, and both training groups significantly increased fat-free weight (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of acute creatine monohydrate supplementation on leucine kinetics and mixed-muscle protein synthesis.

Creatine monohydrate (CrM) supplementation during resistance exercise training results in a greater increase in strength and fat-free mass than placebo. Whether this is solely due to an increase in intracellular water or whether there may be alterations in protein turnover is not clear at this point. We examined the effects of CrM supplementation on indexes of protein metabolism in young healthy men (n = 13) and women (n = 14). Subjects were randomly allocated to CrM (20 g/day for 5 days followed by 5 g/day for 3-4 days) or placebo (glucose polymers) and tested before and after the supplementation period under rigorous dietary and exercise controls. Muscle phosphocreatine, creatine, and total creatine were measured before and after supplementation. A primed-continuous intravenous infusion of L-[1-(13)C]leucine and mass spectrometry were used to measure mixed-muscle protein fractional synthetic rate and indexes of whole body leucine metabolism (nonoxidative leucine disposal), leucine oxidation, and plasma leucine rate of appearance. CrM supplementation increased muscle total creatine (+13.1%, P < 0.05) with a trend toward an increase in phosphocreatine (+8.8%, P = 0.09). CrM supplementation did not increase muscle fractional synthetic rate but reduced leucine oxidation (-19.6%) and plasma leucine rate of appearance (-7.5%, P < 0.05) in men, but not in women. CrM did not increase total body mass or fat-free mass. We conclude that short-term CrM supplementation may have anticatabolic actions in some proteins (in men), but CrM does not increase whole body or mixed-muscle protein synthesis.     

Effect of different frequencies of creatine supplementation on muscle size and strength in young adults

The purpose was to determine if creatine supplementation, consumed immediately before and immediately after exercise, with different dosing frequency (i.e., 2 or 3 d wk) could enhance the gains in muscle size and strength from resistance training (RT) in young adults. A group of 38 physically active, nonresistance trained university students (21-28 years) was randomly allocated to 1 of 4 groups: CR2 (0.15 g·kg creatine during 2 d wk of RT; 3 sets of 10 repetitions; n = 11, 6 men, 5 women), CR3 (0.10 g·kg creatine during 3 d wk of RT; 2 sets of 10 repetitions; n = 11, 6 men, 5 women;), PLA2 (placebo during 2 d wk of RT; n = 8, 5 men, 3 women), and PLA3 (placebo during 3 d wk of RT; n = 8, 4 men, 4 women) for 6 weeks. Before and after training, measurements were taken for muscle thickness of the elbow and knee flexor and extensor muscle groups (ultrasound), 1-repetition maximumleg press and chest press strength, and kidney function (urinary microalbumin). Repeated-measures analysis of variance showed that strength and muscle thickness increased in all groups with training (p < 0.05). The CR2 (0.6 ± 0.9 cm or 20%; p < 0.05) and CR3 groups (0.4 ± 0.6 cm or 16.4%; p < 0.05) experienced greater change in muscle thickness of the elbow flexors compared to the PLA2 (0.05 ± 0.5 cm or 2.3%) and PLA3 groups (0.13 ± 0.7 cm or 6.3%). Men supplementing with creatine experienced a greater increase in leg press strength (77.3 ± 51.2 kg or 62%) compared to women on creatine (21.3 ± 10 kg or 34%, p < 0.05). We conclude that creatine supplementation during RT has a small beneficial effect on regional muscle thickness in young adults but that giving the creatine over 3 d wk did not differ from giving the same dose over 2 d wk.     

Resistance training induces qualitative changes in muscle morphology, muscle architecture, and muscle function in elderly postoperative patients.

Although the negative effects of bed rest on muscle strength and muscle mass are well established, it still remains a challenge to identify effective methods to restore physical capacity of elderly patients recovering from hospitalization. The present study compared different training regimes with respect to muscle strength, muscle fiber size, muscle architecture, and stair walking power in elderly postoperative patients. Thirty-six patients (60-86 yr) scheduled for unilateral hip replacement surgery due to hip osteoarthritis were randomized to either 1) resistance training (RT: 3/wk x 12 wk), 2) electrical stimulation (ES: 1 h/day x 12 wk), or 3) standard rehabilitation (SR: 1 h/day x 12 wk). All measurements were performed at baseline, at 5 wk and 12 wk postsurgery. After 12 wk of resistance training, maximal dynamic muscle strength increased by 30% at 60 degrees /s (P < 0.05) and by 29% at 180 degrees /s (P < 0.05); muscle fiber area increased for type I (+17%, P < 0.05), type IIa (+37%, P < 0.05), and type IIx muscle fibers (+51%, P < 0.05); and muscle fiber pennation angle increased by 22% and muscle thickness increased by 15% (P < 0.05). Furthermore, stair walking power increased by 35% (P < 0.05) and was related to the increase in type II fiber area (r = 0.729, P < 0.05). In contrast, there was no increase in any measurement outcomes with electrical stimulation and standard rehabilitation. The present study is the first to demonstrate the effectiveness of resistance training to induce beneficial qualitative changes in muscle fiber morphology and muscle architecture in elderly postoperative patients. In contrast, rehabilitation regimes based on functional exercises and neuromuscular electrical stimulation had no effect. The present data emphasize the importance of resistance training in future rehabilitation programs for elderly individuals.     

Physical training and heart rate and blood pressure variability: a 5-yr randomized trial

We studied the effect of regular physical activity on cardiac and vascular autonomic modulation during a 5-yr controlled randomized training intervention in a representative sample of older Finnish men. Heart rate variability (HRV) and blood pressure variability (BPV) are markers of cardiac and vascular health, reflecting cardiac and vascular autonomic modulation. One hundred and forty randomly selected 53- to 63-yr-old men were randomized into two identical groups: an intervention (EX) group and a reference (CO) group, of which 89 men remained until the final analysis (EX: n = 47; CO: n = 42). The EX group trained for 30-60 min three to five times a week with an intensity of 40-60% of maximal oxygen consumption. The mean weekly energy expenditure of the training program for the 5-yr training period was 3.80 MJ, and 71% of the EX group exceeded the mean. The EX group had a significantly (P < 0.01) higher oxygen consumption at ventilatory aerobic threshold (VO2VT) than the CO group at the 5-yr time point. VO2VT had a tendency to increase in the EX group and decrease in the CO group (interaction P < 0.001) from the baseline to the 5-yr time point. Peak performance did not change. Low-frequency power of R-R interval variability decreased in the EX group (P < 0.01, by 6%) from the baseline to the 5-yr time point. BPV did not change. In conclusion, low-intensity regular exercise training did not prevent HRV from decreasing or change BPV in 5 yr in older Finnish men.     

Exercise and diet enhance fat oxidation and reduce insulin resistance in older obese adults.

Older, obese, and sedentary individuals are at high risk of developing diabetes and cardiovascular disease. Exercise training improves metabolic anomalies associated with such diseases, but the effects of caloric restriction in addition to exercise in such a high-risk group are not known. Changes in body composition and metabolism during a lifestyle intervention were investigated in 23 older, obese men and women (aged 66 +/- 1 yr, body mass index 33.2 +/- 1.4 kg/m(2)) with impaired glucose tolerance. All volunteers undertook 12 wk of aerobic exercise training [5 days/wk for 60 min at 75% maximal oxygen consumption (Vo(2max))] with either normal caloric intake (eucaloric group, 1,901 +/- 277 kcal/day, n = 12) or a reduced-calorie diet (hypocaloric group, 1,307 +/- 70 kcal/day, n = 11), as dictated by nutritional counseling. Body composition (decreased fat mass; maintained fat-free mass), aerobic fitness (Vo(2max)), leptinemia, insulin sensitivity, and intramyocellular lipid accumulation (IMCL) in skeletal muscle improved in both groups (P < 0.05). Improvements in body composition, leptin, and basal fat oxidation were greater in the hypocaloric group. Following the intervention, there was a correlation between the increase in basal fat oxidation and the decrease in IMCL (r = -0.53, P = 0.04). In addition, basal fat oxidation was associated with circulating leptin after (r = 0.65, P = 0.0007) but not before the intervention (r = 0.05, P = 0.84). In conclusion, these data show that exercise training improves resting substrate oxidation and creates a metabolic milieu that appears to promote lipid utilization in skeletal muscle, thus facilitating a reversal of insulin resistance. We also demonstrate that leptin sensitivity is improved but that such a trend may rely on reducing caloric intake in addition to exercise training.     

Plasma adiponectin concentration in healthy pre- and postmenopausal women: relationship with body composition, bone mineral, and metabolic variables

The aim of the current investigation was to determine the possible relationships of fasting adiponectin level with body composition, bone mineral, insulin sensitivity, leptin, and cardiorespiratory fitness parameters in 153 women. Subjects were classified as premenopausal (n = 42; 40.8 +/- 5.7 yr) if they had regular menstrual periods, early postmenopausal (n = 49; 56.7 +/- 3.6 yr) if they had been postmenopausal for more than >1 yr but <7 yr (5.5 +/- 1.3 yr), and postmenopausal (n = 62; 72.2 +/- 4.5 yr) if they had been postmenopausal for >7 yr. All women studied had a body mass index (BMI) <30 kg/m(2). Adiponectin values were higher (P < 0.05) in middle-aged (12.0 +/- 5.1 microg/ml) and older (15.3 +/- 7.3 microg/ml) postmenopausal women compared with middle-aged premenopausal women (8.4 +/- 3.2 microg/ml). Mean plasma adiponectin concentration in the total group of women (n = 153) was 12.2 +/- 6.3 microg/ml and was positively related (P < 0.05) to age, indexes of overall obesity (BMI, body fat mass), and cardiorespiratory fitness (PWC) values. In addition, a negative association (P < 0.05) between adiponectin with central obesity (waist-to-hip and waist-to-thigh ratio), fat-free mass, bone mineral (bone mineral content, total and lumbar spine bone mineral density), and leptin and insulin resistance (insulin, fasting insulin resistance index) values was observed. However, multivariate regression analysis revealed that only age, fasting insulin resistance index, and leptin were independent predictors of adiponectin concentration. In conclusion, circulating adiponectin concentrations increase with age in normal-weight middle-aged and older women. It appears that adiponectin is independently related to age, leptin, and insulin resistance values in women across the age span and menstrual status.     

Preferential reductions in intermuscular and visceral adipose tissue with exercise-induced weight loss compared with calorie restriction

Intermuscular adipose tissue (IMAT) and visceral adipose tissue (VAT) are associated with insulin resistance. We sought to determine whether exercise-induced weight loss (EX) results in greater reductions in IMAT and VAT compared with similar weight loss induced by calorie restriction (CR) and whether these changes are associated with improvements in glucoregulation. Sedentary men and women (50-60 yr; body mass index of 23.5-29.9 kg/m(2)) were randomized to 1 yr of CR (n = 17), EX (n = 16), or a control group (CON; n = 6). Bilateral thigh IMAT and VAT volumes were quantified using multi-slice magnetic resonance imaging. Insulin sensitivity index (ISI) was determined from oral glucose tolerance test glucose and insulin levels. Weight loss was comparable (P = 0.25) in the CR (-10.8 ± 1.4%) and EX groups (-8.3 ± 1.5%) and greater than in the control group (-2.0 ± 2.4%; P < 0.05). IMAT and VAT reductions were larger in the CR and EX groups than in the CON group (P ≤ 0.05). After controlling for differences in total fat mass change between the CR and EX groups, IMAT and VAT reductions were nearly twofold greater (P ≤ 0.05) in the EX group than in the CR group (IMAT: -45 ±5 vs. -25 ± 5 ml; VAT: -490 ± 64 vs. -267 ± 61 ml). In the EX group, the reductions in IMAT were correlated with increases in ISI (r = -0.71; P = 0.003), whereas in the CR group, VAT reductions were correlated with increases in ISI (r = -0.64; P = 0.006). In conclusion, calorie restriction and exercise-induced weight loss both decrease IMAT and VAT volumes. However, exercise appears to result in preferential reductions in these fat depots.     

Human skeletal muscle creatine transporter mRNA and protein expression in healthy,young males and females

The present study investigated whether there were any differences between males and females in respect to creatine transporter (CreaT) gene expression and/or total creatine (TCr) content in human vastus lateralis muscle. Skeletal muscle obtained from young healthy male (n = 13, age: 23.2 ± 5.0 years) and female subjects (n = 12, age: 21.7 ± 4.3 years) was analyzed for CreaT mRNA, CreaT protein and TCr content. Total CreaT protein content in the muscle was similar (p > 0.05) between the sexes. Two bands (~ 55 and 73 kDa) of the CreaT protein were detected in all muscle samples. Both the 55 and the 73 kDa bands were present in similar (p > 0.05) amounts in males compared with females. The 73 kDa band was in greater abundance (p < 0.05) than the 55 kDa band, irrespective of gender. In addition, CreaT mRNA expression relative to -actin mRNA and the TCr content (males: 117.8 ± 2.2, females: 125.3 ± 4.3 mmol.kg^–1 dry mass) were also unaffected (p > 0.05) by gender. These data demonstrate that gender does not influence skeletal muscle TCr content and CreaT gene expression in young human subjects.     

Effects of training and creatine supplement on muscle strength and body mass

The purpose of this study was to test the effect of creatine supplement on the size of the extra- and intracellular compartments and on the increase of isokinetic force during a strength training-program. Twenty-five healthy male subjects (age 22.0+/-2.9 years) participated in this experiment. Seven subjects formed the control-group. They did not complete any training and did not have any dietary supplement. The eighteen other subjects were randomly divided into a creatine- (n = 8) and a placebo-group (n = 10). They were submitted to a controlled strength-training program for 42 days followed by a detraining period of 21 days. Creatine and placebo were given over a period of 9 weeks. The size of the body water compartments was assessed by bioimpedance spectroscopy and the isokinetic force was determined during a single squat by means of an isokinetic dynamometer. These measurements were completed beforehand, at the end of the training period, and after the determining period. Both placebo- and creatine-group increased the isokinetic force by about 6% after the training period, showing that creatine ingestion does not induce a higher increase of the force measured during a single movement. No change in body mass was observed in the control- and placebo-groups during the entire experiment period while the body mass of the creatine-group was increased by 2 kg (P < 0.001). This change can be attributed partially to an increase (P = 0.039) in the body water content (+1.11), and more specifically, to an increase (P < 0.001) in the volume of the inter-cellular compartment (+0.61). Nevertheless, the relative volumes of the body water compartments remained constant and therefore the gain in body mass cannot be attributed to water retention, but probably to dry matter growth accompanied with a normal water volume.     

Gender difference in cardiovagal baroreflex gain in humans.

We tested the hypothesis that women would demonstrate lower cardiovagal baroreflex gain compared with men. If so, we further hypothesized that the lower cardiovagal baroreflex gain in women would be associated with their lower aerobic fitness and higher body fat percentage compared with men. To accomplish this, we measured cardiovagal baroreflex gain (modified Oxford technique) in sedentary, nonobese (body mass index < 25 kg/m2) men (age = 26.0 +/- 2.1 yr, n = 11) and women (age = 26.9 +/- 1.6 yr, n = 14). Resting R-R interval and diastolic blood pressure were similar in the two groups, but systolic blood pressure was lower (P < 0.05) in the women. Cardiovagal baroreflex gain was significantly lower in the women compared with the men (13.3 +/- 1.5 vs. 20.0 +/- 2.8 ms/mmHg, P < 0.05). The lower cardiovagal baroreflex gain in the women was not related (P > 0.05) to their lower aerobic fitness and was only marginally related to their higher body fat percentage (r = -0.34, P < 0.05). There were no gender differences in the threshold and saturation, operating range, or operating point (all P > 0.05), although the operating point fell significantly to left (i.e., at a lower systolic blood pressure) compared with men. Therefore, the findings of this study suggest that the gain of the cardiovagal baroreflex is reduced whereas other parameters were similar in women compared with men. The mechanisms responsible for the reduced cardiovagal baroreflex gain remain unclear.     

Resistance training increases total daily energy expenditure in disabled older women with coronary heart disease.

Physical activity energy expenditure (PAEE) is a determinant of prognosis and fitness in older patients with coronary heart disease (CHD). PAEE and total energy expenditure (TEE) are closely related to fatness, physical function, and metabolic risk in older individuals. The goal of this study was to assess effects of resistance training on PAEE, TEE, and fitness in older women with chronic CHD and physical activity limitations (N = 51, mean age: 72 + 5 yr). The study intervention consisted of a progressive, 6-mo program of resistance training vs. a control group condition of low-intensity yoga and deep breathing. The study interventions were completed by 42 of the 51 participants. The intervention group manifested a 177 +/- 213 kcal/day (+9%) increase in TEE, pre- to posttraining, measured by the doubly labeled water technique during a nonexercise 10-day period (P < 0.03 vs. controls). This was due to a 50 +/- 74 kcal/day (4%) increase in resting metabolic rate measured by indirect calorimetry (P < 0.01, P < 0.05 vs. controls) and a 123 +/- 214 kcal/day (9%) increase in PAEE (P < 0.03, P = 0.12 vs. controls). Resistance training was associated with significant increases in upper and lower body strength, but no change in fat-free mass, measured by dual X-ray absorptiometry, or left ventricular function, measured by echocardiography and Doppler. Women in the control group showed no alterations in TEE or its determinants. There were no changes between groups in body composition, aerobic capacity, or measures of mental depression. These results demonstrate that resistance training of 6-mo duration leads to an increase in TEE and PAEE in older women with chronic CHD.