Ratings of perceived exertion in active muscle during high-intensity and low-intensity resistance exercise

This investigation compared ratings of perceived exertion specific to the active muscles used during resistance exercise (RPE-AM) using the 15-category Borg scale during high-intensity (HIP) and low-intensity (LIP) weight lifting. Ten men (23.2 +/- 3.6 years) and 10 women (21.8 +/- 2.7 years) performed 2 trials consisting of seven exercises: bench press (BP), leg press, latissimus dorsi pull down, triceps press, biceps curl, shoulder press, and calf raise. The HIP and LIP protocols were completed in counterbalanced order. During HIP, subjects completed 5 repetitions using 90% of 1 repetition maximum (1RM). RPE-AM was measured after every repetition. During LIP, subjects completed 15 repetitions using 30% of 1RM. RPE-AM was measured after every third repetition. RPE-AMs were greater (p 相似文献   

Effect of training on the GH/IGF-I axis during exercise in middle-aged men: relationship to glucose homeostasis

The aim of this study was to compare circulating levels of growth hormone (GH), IGF-I, and IGF-binding protein (IGFBP)-1 and IGFBP-3 in response to a long-duration endurance exercise in trained vs. sedentary middle-aged males and to determine whether a relationship with glucose homeostasis exists. Seven trained men (Tr) were compared with seven age-matched sedentary men (Sed) during two trials of 60 min of cycling exercise performed below (-VT) and above (+VT) the ventilatory threshold. Insulin sensitivity (S(I)) was higher in Tr than in Sed (P < 0.001). Basal GH, IGF-I, and IGFBP-1 and -3 were higher in Tr (P < 0.05). During +VT, Tr had a threefold higher GH response, whereas their blood glucose level was better maintained (P < 0.05). Basal IGFBP-1 was correlated with S(I) (P < 0.01). These data indicate that endurance training in middle-aged men increased the activity of the GH/IGF-I system and improved glucoregulation both at rest and during high-intensity endurance exercise.     

Carbohydrate supplementation and perceived exertion during resistance exercise

The purpose of the present study was to investigate the relationship between carbohydrate energy substrate and the perception of exertion during resistance exercise. Thirty strength-trained subjects were randomized to a carbohydrate group (C) or a placebo group (P), and lifted weights for 2 hours (4 sets; 10 repetitions maximum; 10 exercises; 2-3-minute rest intervals). Subjects ingested 10 ml.kg(-1).h(-1) of 6% carbohydrate or placebo beverages during the resistance-training bout. The 15-category Borg Perceived Exertion Scale was used to assess overall body (RPE-O) and active muscle (RPE-AM) perceived exertion after completion of the last repetition in each set for each exercise. No significant differences were found between the C and P groups for either RPE-O or RPE-AM, with the exception of RPE-O for the upright row and back squat (p < 0.05). Carbohydrate supplementation exerted no attenuating effect on ratings of perceived exertion (RPE) during resistance training.     

Moderate resistance training volume produces more favorable strength gains than high or low volumes during a short-term training cycle

The purpose of this study was to examine the effects of 3 resistance training volumes on maximal strength in the snatch (Sn), clean & jerk (C&J), and squat (Sq) exercises during a 10-week training period. Fifty-one experienced (>3 years), trained junior lifters were randomly assigned to one of 3 groups: a low-volume group (LVG, n = 16), a moderate-volume group (MVG, n = 17), and a high-volume group (HVG, n = 18). All subjects trained 4-5 days a week with a periodized routine using the same exercises and relative intensities but a different total number of sets and repetitions at each relative load: LVG (1,923 repetitions), MVG (2,481 repetitions), and HVG (3,030 repetitions). The training was periodized from moderate intensity (60- 80% of 1 repetition maximum [1RM]) and high number of repetitions per set (2-6) to high intensity (90-100% of 1RM) and low number of repetitions per set (1-3). During the training period, the MVG showed a significant increase for the Sn, C&J, and Sq exercises (6.1, 3.7, and 4.2%, respectively, p < 0.01), whereas in the LVG and HVG, the increase took place only with the C&J exercise (3.7 and 3%, respectively, p < 0.05) and the Sq exercise (4.6%, p < 0.05, and 4.8%, p < 0.01, respectively). The increase in the Sn exercise for the MVG was significantly higher than in the LVG (p = 0.015). Calculation of effect sizes showed higher strength gains in the MVG than in the HVG or LVG. There were no significant differences between the LVG and HVG training volume-induced strength gains. The present results indicate that junior experienced lifters can optimize performance by exercising with only 85% or less of the maximal volume that they can tolerate. These observations may have important practical relevance for the optimal design of strength training programs for resistance-trained athletes, since we have shown that performing at a moderate volume is more effective and efficient than performing at a higher volume.     

The effects of chronic betaine supplementation on exercise performance, skeletal muscle oxygen saturation and associated biochemical parameters in resistance trained men

Trepanowski, JF, Farney, TM, McCarthy, CG, Schilling, BK, Craig, SA, and Bloomer, RJ. The effects of chronic betaine supplementation on exercise performance, skeletal muscle oxygen saturation, and associated biochemical parameters in resistance trained men. J Strength Cond Res 25(12): 3461-3471, 2011-We examined the effects of chronic betaine supplementation on exercise performance and associated parameters in resistance trained men. Men were randomly assigned in a double-blind manner using a crossover design to consume betaine (2.5 g of betaine mixed in 500 ml of Gatorade?) or a placebo (500 ml of Gatorade?) for 14 days, with a 21-day washout period. Before and after each treatment period, tests of lower- and upper-body muscular power and isometric force were conducted, including a test of upper-body muscular endurance (10 sets of bench press exercise to failure). Muscle tissue oxygen saturation (StO2) during the bench press protocol was measured via near infrared spectroscopy. Blood samples were collected before and after the exercise test protocol for analysis of lactate, nitrate/nitrite (NOx), and malondialdehyde (MDA). When analyzed using a repeated measures analysis of variance, no significant differences were noted between conditions for exercise performance variables (p > 0.05). However, an increase in total repetitions (p = 0.01) and total volume load (p = 0.02) in the 10-set bench press protocol was noted with betaine supplementation (paired t-tests), with values increasing approximately 6.5% from preintervention to postintervention. Although not of statistical significance (p = 0.14), postexercise blood lactate increased to a lesser extent with betaine supplementation (210%) compared with placebo administration (270%). NOx was lower postintervention as compared with preintervention (p = 0.06), and MDA was relatively unchanged. The decrease in StO2 during the bench press protocol was greater with betaine vs. placebo (p = 0.01), possibly suggesting enhanced muscle oxygen consumption. These findings indicate that betaine supplementation results in a moderate increase in total repetitions and volume load in the bench press exercise, without favorably impacting other performance measures.     

Aging, exercise, and endothelial progenitor cell clonogenic and migratory capacity in men.

Numerical and functional impairment of circulating endothelial progenitor cells (EPCs) is thought to contribute to vascular aging and the associated increase in cardiovascular risk. We tested the following hypotheses: 1) EPC clonogenic and migratory capacity decrease progressively with age in healthy, sedentary adult men; and 2) regular aerobic exercise will improve EPC clonogenic and migratory capacity in previously sedentary middle-aged and older men. Peripheral blood samples were collected from 46 healthy sedentary men: 10 young (26 +/- 1 yr), 15 middle-aged (47 +/- 1 yr), and 21 older (63 +/- 1 yr). Mononuclear cells were isolated and preplated for 2 days, and nonadherent cells were further cultured for 7 days to determine EPC colony-forming units. Migratory activity of EPCs was determined using a modified Boyden chamber. Ten sedentary middle-aged and older men (59 +/- 3 yr) were studied before and after a 3-mo aerobic exercise intervention. The number of EPC colony-forming units was approximately 75% lower (P < 0.01) in middle-aged (12 +/- 3) and older (8 +/- 2) compared with young (40 +/- 7) men. There was no difference in colony count between middle-aged and older men. EPC migration (fluorescent units) was significantly reduced in older (453 +/- 72) compared with young (813 +/- 114) and middle-aged (760 +/- 114) men. The exercise intervention increased (P < 0.05) both EPC colony-forming units (10 +/- 3 to 22 +/- 5) and migratory activity (683 +/- 96 to 1,022 +/- 123) in previously sedentary middle-aged and older men. These results provide further evidence that aging adversely affects EPC function. Regular aerobic-endurance exercise, however, is an effective lifestyle intervention strategy for improving EPC clonogenic and migratory capacity in middle-aged and older healthy men.     

Collagen gene expression in rat left ventricle: interactive effect of age and exercise training.

Whether or not exercise training of sufficient intensity and duration to produce left ventricle (LV) hypertrophy also regulates deposition of interstitial collagen and cross-linking at the pretranslational level is unknown. Therefore, the effects of exercise training on gene expression for the two principal fibrillar collagens in LV, types I and III, were assessed in young adult (5 mo), middle-aged (15 mo), and old (26 mo) rats. We also evaluated the potential interaction of changes in mRNA for these procollagens with alterations in LV extracellular matrix characteristics by simultaneously measuring collagen concentration (hydroxyproline) and extent of mature collagen cross-linking (hydroxylysylpyridinoline, HP). Ten weeks of treadmill running resulted in LV hypertrophy and an increased maximal oxygen uptake in all three age groups of trained rats compared with sedentary controls. Percent collagen in rat LV almost doubled (P < 0.0001) from 5 to 26 mo of age, an increase unaffected by exercise training. With aging, a significant decline in expression of mRNAs for both collagen type I (P < 0.005) and type III (P < 0.001) was observed in LV free wall (LVF) but not septum (LVS). Training prevented this decline in LVF mRNAs for the two principal fibrillar collagens in middle-aged rats whereas it attenuated the decline in senescent animals. HP concentration increased significantly with aging in both LVF (P < 0.005) and LVS (P < 0.01). Training modulated this effect, but again only in LVF, so that HP was significantly lower (P < 0.05) in this region of the LV in old trained rats compared with sedentary counterparts. We conclude that exercise training modulates the effects of aging on collagen gene mRNAs and HP cross-linking regionally within the LV.     

S(G), S(I), and EGP of exercise-trained middle-aged men estimated by a two-compartment labeled minimal model

To examine the effects of physical training on glucose effectiveness (S(G)), insulin sensitivity (S(I)), and endogenous glucose production (EGP) in middle-aged men, stable-labeled frequently sampled intravenous glucose tolerance tests (FSIGTT) were performed on 11 exercise-trained middle-aged men and 12 age-matched sedentary men. The time course of EGP during the FSIGTT was estimated by nonparametric stochastic deconvolution. Glucose uptake-specific indexes of glucose effectiveness (S(2*)(G) x 10(2): 0.81 +/- 0.08 vs. 0.60 +/- 0.05 dl. min(-1). kg(-1), P < 0.05) and insulin sensitivity [S(2*)(I) x 10(4): 24.59 +/- 2.98 vs. 11.89 +/- 2.36 dl. min(-1). (microU/ml)(-1). kg(-1), P < 0.01], which were analyzed using the two-compartment minimal model, were significantly greater in the trained group than in the sedentary group. Plasma clearance rate (PCR) of glucose was consistently greater in the trained men than in sedentary men throughout FSIGTT. Compared with sedentary controls, EGP of trained middle-aged men was higher before glucose load. The EGP of the two groups was similarly suppressed by approximately 70% within 10 min, followed by an additional suppression after insulin infusion. EGP returned to basal level at approximately 60 min in the trained men and at 100 min in the controls, followed by its overshoot, which was significantly greater in the trained men than in the controls. In addition, basal EGP was positively correlated with S(2*)(G) . The higher basal EGP and greater EGP overshoot in trained middle-aged men appear to compensate for the increased insulin-independent (S(2*)(G)) and -dependent (S(2*)(I)) glucose uptake to maintain glucose homeostasis.     

5'-AMP-activated protein kinase activity and subunit expression in exercise-trained human skeletal muscle.

5'-AMP-activated protein kinase (AMPK) has been proposed to be a pivotal factor in cellular responses to both acute exercise and exercise training. To investigate whether protein levels and gene expression of catalytic (alpha(1), alpha(2)) and regulatory (beta(1), beta(2), gamma(1), gamma(2), gamma(3)) AMPK subunits and exercise-induced AMPK activity are influenced by exercise training status, muscle biopsies were obtained from seven endurance exercise-trained and seven sedentary young healthy men. The alpha(1)- and alpha(2)-AMPK mRNA contents in trained subjects were both 117 +/- 2% of that in sedentary subjects (not significant), whereas mRNA for gamma(3) was 61 +/- 1% of that in sedentary subjects (not significant). The level of alpha(1)-AMPK protein in trained subjects was 185 +/- 34% of that in sedentary subjects (P < 0.05), whereas the levels of the remaining subunits (alpha(2), beta(1), beta(2), gamma(1), gamma(2), gamma(3)) were similar in trained and sedentary subjects. At the end of 20 min of cycle exercise at 80% of peak O(2) uptake, the increase in phosphorylation of alpha-AMPK (Thr(172)) was blunted in the trained group (138 +/- 38% above rest) compared with the sedentary group (353 +/- 63% above rest) (P < 0.05). Acetyl CoA-carboxylase beta-phosphorylation (Ser(221)), which is a marker for in vivo AMPK activity, was increased by exercise in both groups but to a lower level in trained subjects (32 +/- 5 arbitrary units) than in sedentary controls (45 +/- 1 arbitrary units) (P < 0.01). In conclusion, trained human skeletal muscle has increased alpha(1)-AMPK protein levels and blunted AMPK activation during exercise.     

Relationship between the number of repetitions and selected percentages of one repetition maximum in free weight exercises in trained and untrained men

Resistance exercise intensity is commonly prescribed as a percent of 1 repetition maximum (1RM). However, the relationship between percent 1RM and the number of repetitions allowed remains poorly studied, especially using free weight exercises. The purpose of this study was to determine the maximal number of repetitions that trained (T) and untrained (UT) men can perform during free weight exercises at various percentages of 1RM. Eight T and 8 UT men were tested for 1RM strength. Then, subjects performed 1 set to failure at 60, 80, and 90% of 1RM in the back squat, bench press, and arm curl in a randomized, balanced design. There was a significant (p < 0.05) intensity x exercise interaction. More repetitions were performed during the back squat than the bench press or arm curl at 60% 1RM for T and UT. At 80 and 90% 1RM, there were significant differences between the back squat and other exercises; however, differences were much less pronounced. No differences in number of repetitions performed at a given exercise intensity were noted between T and UT (except during bench press at 90% 1RM). In conclusion, the number of repetitions performed at a given percent of 1RM is influenced by the amount of muscle mass used during the exercise, as more repetitions can be performed during the back squat than either the bench press or arm curl. Training status of the individual has a minimal impact on the number of repetitions performed at relative exercise intensity.     

Influence of moderately intense strength training on flexibility in sedentary young women

The present study is the first to examine whether moderately intense resistance training improves flexibility in an exclusively young, sedentary women population. Twenty-four, young, sedentary women were divided into 3 groups as follows: agonist/antagonist (AA) training group, alternated strength training (AST) group, or a control group (CG). Training occurred every other day for 8 weeks for a total of 24 sessions. Training groups performed 3 sets of 10 to 12 repetitions per set except for abdominal training where 3 sets of 15 to 20 reps were performed. Strength (1 repetition maximum bench press) and flexibility were assessed before and after the training period. Flexibility was assessed on 6 articular movements: shoulder flexion and extension, horizontal shoulder adduction and abduction, and trunk flexion and extension. Both groups increased strength and flexibility significantly from baseline and significantly when compared with the CG (p ≤ 0.05). The AST group increased strength and flexibility significantly more than the AA group (p ≤ 0.05) in all but one measurement. This study shows that resistance training can improve flexibility in young sedentary women in 8 weeks.     

Effects of age on testosterone responses to resistance exercise and musculoskeletal variables in men

This study compared serum total testosterone (TT) and free testosterone (FT) responses of young (20-26 years, n = 8), middle-aged (38-53 years, n = 7), and older (59-72 years, n = 9) men to resistance exercise. We also examined the relationships between testosterone (T) levels and strength, bone mineral density (BMD), and body composition variables for each age group. Subjects were tested for isotonic muscular strength (1 repetition maximum [1RM]), BMD (dual-energy x-ray absorptiometry [DXA]) and body composition (DXA). Each group performed an acute exercise protocol (3 sets, 10 repetitions, 80% of 1RM, 6 exercises). Blood samples were obtained at baseline, immediately postexercise, and 15 minutes postexercise for the TT and FT assays. The older age group had significantly (p < 0.05) lower T levels than the young group, but each group exhibited an increase (p < 0.05) in TT and FT immediately postexercise. Total T and FT were significantly correlated (p < 0.05) with strength in middle-aged and older men and with bone-free lean tissue mass in older men. In conclusion, middle-aged and older men showed similar relative T responses to those of younger men to a single bout of high-intensity resistance exercise. However, T levels were related to strength and muscle mass only in middle-aged or older men. On a practical application level, older men can complete a high-intensity resistance exercise program resulting in spikes in T that may attenuate age-related muscle and BMD loss.     

A comparative electromyographical investigation of muscle utilization patterns using various hand positions during the lat pull-down

This study aimed at investigating the effects of different hand positions on the electromyographic (EMG) activity of shoulder muscles during the performance of the lat pull-down exercise. Ten healthy men performed 3 repetitions of the lat pull-down exercise using their experimentally determined 10RM (repetition maximum) weight. Four different common variations of the lat pull-down were used: close grip (CG), supinated grip (SG), wide grip anterior (WGA), and wide grip posterior (WGP). Normalized root mean square of the EMG (NrmsEMG) activity for the right posterior deltoid (PD), latissimus dorsi (LD), pectoralis major (PM), teres major (TM), and long head of the triceps (TLH) were recorded using surface electrodes and normalized using maximum voluntary contractions. Repeated measures analysis of variance for each muscle detected statistical differences (p < 0.05) in myoelectric activity among hand positions during both the concentric and eccentric phases of the exercise. During the concentric phase, NrmsEMG results for the LD included WGA > WGP, SG, CG. For the TLH: WGA > WGP, SG, CG and WGP > CG, SG. For the PD: CG, WGA, SG > WGP. For the PM: CG, WGA, SG > WGP. During the eccentric phase, the LD produced the following patterns: WGA > WGP, SG, CG and WGP > CG. The TLH pattern showed WGA > SG and CG. For the PD: CG > WGA, WGP. The results indicate that changes in handgrip position affect the activities of specific muscles during the lat pull-down movement. Also, performance of the lat pull-down exercise using the WGA hand position produces greater muscle activity in the LD than any other hand position during both the concentric or eccentric phases of the movement.     

Exercise training alleviates MCT1 and MCT4 reductions in heart and skeletal muscles of STZ-induced diabetic rats.

We compared the changes in monocarboxylate transporter 1 (MCT1) and 4 (MCT4) proteins in heart and skeletal muscles in sedentary control and streptozotocin (STZ)-induced diabetic rats (3 wk) and in trained (3 wk) control and STZ-induced diabetic animals. In nondiabetic animals, training increased MCT1 in the plantaris (+51%; P < 0.01) but not in the soleus (+9%) or the heart (+14%). MCT4 was increased in the plantaris (+48%; P < 0.01) but not in the soleus muscles of trained nondiabetic animals. In sedentary diabetic animals, MCT1 was reduced in the heart (-30%), and in the plantaris (-31%; P < 0.01) and soleus (-26%) muscles. MCT4 content was also reduced in sedentary diabetic animals in the plantaris (-52%; P < 0.01) and soleus (-25%) muscles. In contrast, in trained diabetic animals, MCT1 and MCT4 in heart and/or muscle were similar to those of sedentary, nondiabetic animals (P > 0.05) but were markedly greater than in the sedentary diabetic animals [MCT1: plantaris +63%, soleus +51%, heart +51% (P > 0.05); MCT4: plantaris +107%, soleus +17% (P > 0.05)]. These studies have shown that 1) with STZ-induced diabetes, MCT1 and MCT4 are reduced in skeletal muscle and/or the heart and 2) exercise training alleviated these diabetes-induced reductions.     

Influence of strength training on adult women's flexibility

The purpose of the current study was to investigate the effect of 10 weeks of strength training on the flexibility of sedentary middle-aged women. Twenty women were randomly assigned to either a strength training group (n = 10; age, 37 +/- 1.7 years; body mass, 65.2 +/- 10.7 kg; height, 157.7 +/- 10.8 cm; and body mass index, 25.72 +/- 3.3 kg x m(-2)) or a control group (n = 10; age, 36.9 +/- 1.2 years; body mass, 64.54 +/- 10.18 kg; height, 158.1 +/- 8.9 cm; and body mass index, 26.07 +/- 2.8 kg x m(-2)). The strength training program was a total body session performed in a circuit fashion and consisted of 7 exercises performed for 3 circuits of 8 to 12 repetitions maximum (RM), except for the abdominal exercise which was performed for 15 to 20 RM. Flexibility measurements were taken for 10 articulation movements pre and post training: shoulder flexion and extension, shoulder horizontal adduction and abduction, elbow flexion, hip flexion and extension, knee flexion, and trunk flexion and extension. Pre and post training, 10 RM strength significantly increased (p < 0.05). Of the movements examined, only shoulder horizontal adduction, hip flexion and extension, and trunk flexion and extension demonstrated significant increases (p < 0.05). Neither elbow nor knee flexion showed a significant change with weight training. The control group showed no significant change in any of the flexibility measures determined. In conclusion, weight training can increase flexibility in previously sedentary middle-aged women in some, but not all joint movements.     

Lack of age-related decreases in basal whole leg blood flow in resistance-trained men.

Reductions in basal leg blood flow have been implicated in the pathogenesis of metabolic syndrome and functional impairment in humans. We tested the hypothesis that reductions in basal whole leg blood flow with age are either absent or attenuated in those who perform regular strength training. A total of 104 normotensive men aged 20-34 yr (young) and 35-65 yr (middle aged), who were either sedentary or resistance trained, were studied. Mean and diastolic blood pressures were higher (P < 0.05-0.001) in the middle-aged compared with the young men, but there were no significant differences between the sedentary and resistance-trained groups. In the sedentary group, basal whole leg blood flow (duplex Doppler ultrasound) and vascular conductance were lower ( approximately 30 and approximately 38%, respectively; P < 0.01) in the middle-aged compared with the young men. There were no such age-related differences in the resistance-trained group. In the young men, basal whole leg blood flow and vascular conductance were not different between the two activity groups, but, in the middle-aged men, they were higher ( approximately 35 and approximately 36%, respectively; P < 0.01) in the resistance-trained men than in the sedentary men. When blood flow and vascular conductance were expressed relative to the leg muscle mass, the results were essentially the same. We concluded that the age-related reduction in basal whole leg blood flow is absent in resistance-trained men. These results suggest that resistance training may favorably influence leg perfusion in aging humans, independent of its impact on leg muscle mass.     

HSP72 as a complementary protection against oxidative stress induced by exercise in the soleus muscle of rats

Given the potential of reactive oxygen species to damage intracellular proteins during subsequent bouts of muscle contractions, it was suggested that, when this production exceeds the antioxidant capacity, the preexisting antioxidant pathways may be complemented by the synthesis of the defense mechanism represented by heat shock proteins (HSPs), stress proteins with the function of repair and maintaining protein folding. To test this hypothesis, we analyzed reactive carbonyl derivatives in plasma and the expression of HSP72 and activities of enzymes from the oxidative and antioxidant defense systems in the soleus muscle of sedentary rats and rats trained by two protocols: continuous and intermittent. We analyzed all three groups at rest and 2 h after acute exercise. After 8 wk of training, the animals from both groups clearly demonstrated higher resistance to exercise. Both trained groups showed significantly higher citrate synthase, catalase, and glutathione reductase activities than the control group (P < 0.01). After acute exercise, catalase and glutathione reductase activities significantly decreased (P < 0.01) and plasma reactive carbonyl derivatives significantly increased (P < 0.05) in the sedentary group, suggesting an oxidative-stress condition as responsible for exhaustion in this group. Finally, after acute exercise, the induction of HSP72 expression occurred only in the sedentary group, suggesting that HSP72 acts as a complementary protective mechanism in exercise-induced oxidative stress.     

Exercise effects on chromium excretion of trained and untrained men consuming a constant diet

Chromium excretion of eight trained and five sedentary men was determined on rest days and after exercise to exhaustion at 90% of maximum O2 consumption (VO2max) to determine if degree of physical fitness affects urinary Cr losses. Subjects were fed a constant daily diet containing approximately 9 micrograms Cr/1,000 kcal. VO2max of the trained runners was in the good or above range based on their age and that of the sedentary subjects was average or below. While consuming the control diet, basal urinary Cr excretion of subjects who exercise regularly was significantly lower than that of the sedentary control subjects, 0.09 +/- 0.01 and 0.21 +/- 0.03 microgram/day (mean +/- SE), respectively. When subjects consumed self-chosen diets, basal urinary Cr excretion of the trained subjects was also significantly lower than that of the untrained subjects. Daily urinary Cr excretion of trained subjects was significantly higher on the day of a single exercise bout at 90% VO2max compared with nonexercise days, 0.12 +/- 0.02 and 0.09 +/- 0.01 microgram/day, respectively. Urinary Cr excretion of sedentary subjects was not altered after controlled exercise. These data demonstrate that basal urinary Cr excretion and excretion in response to exercise are related to VO2max and therefore degree of physical fitness.     

Experimental chronic low‐frequency resistance training produces skeletal muscle hypertrophy in the absence of muscle damage and metabolic stress markers

Volitional animal resistance training constitutes an important approach to modeling human resistance training. However, the lack of standardization protocol poses a frequent impediment to the production of skeletal muscle hypertrophy and the study of related physiological variables (i.e., cellular damage/inflammation or metabolic stress). Therefore, the purposes of the present study were: (1) to test whether a long‐term and low frequency experimental resistance training program is capable of producing absolute increases in muscle mass; (2) to examine whether cellular damage/inflammation or metabolic stress is involved in the process of hypertrophy. In order to test this hypothesis, animals were assigned to a sedentary control (C, n = 8) or a resistance trained group (RT, n = 7). Trained rats performed 2 exercise sessions per week (16 repetitions per day) during 12 weeks. Our results demonstrated that the resistance training strategy employed was capable of producing absolute mass gain in both soleus and plantaris muscles (12%, p < 0.05). Furthermore, muscle tumor necrosis factor (TNF‐α) protein expression (soleus muscle) was reduced by 24% (p < 0.01) in trained group when compared to sedentary one. Finally, serum creatine kinase (CK) activity and serum lactate concentrations were not affected in either group. Such information may have practical applications if reproduced in situations where skeletal muscle hypertrophy is desired but high mechanical stimuli of skeletal muscle and inflammation are not. Copyright © 2010 John Wiley & Sons, Ltd.     

Aerobic training reduces oxidative stress in skeletal muscle of rats exposed to air pollution and supplemented with chromium picolinate

Objective: The purpose of this study was to investigate the effects of chromium picolinate (CrPic) supplementation associated with aerobic exercise using measures of oxidative stress in rats exposed to air pollution.

Methods: Sixty-one male Wistar rats were divided into eight groups: residual oil fly ash (ROFA) exposure and sedentary (ROFA-SED); ROFA exposure, sedentary and supplemented (ROFA-SED-CrPic); ROFA exposure and trained (ROFA-AT); ROFA exposure, supplemented and trained (ROFA-AT-CrPic); sedentary (Sal-SED); sedentary and supplemented (Sal-SED-CrPic); trained (Sal-AT); and supplemented and trained (Sal-AT-CrPic). Rats exposed to ROFA (air pollution) received 50?µg of ROFA daily via intranasal instillation. Supplemented rats received CrPic (1?mg/kg/day) daily by oral gavage. Exercise training was performed on a rat treadmill (5×/week). Oxidative parameters were evaluated at the end of protocols.

Results: Trained groups demonstrated lower gain of body mass (P?P?P?P?=?.0014), although CAT activity did not differ among groups (P?=?.4487).

Conclusion: Air pollution exposure did not lead to alterations in oxidative markers in lungs and heart, and exercise training was responsible for decreasing oxidative stress of the gastrocnemius.