Creatine supplementation improves muscular performance in older men

PURPOSE: Creatine supplementation has been shown to enhance muscle strength and power after only 5-7 d in young adults. Creatine supplementation could therefore benefit older individuals because aging is associated with a decrease in muscle strength and explosive power. METHODS: We examined the effects of 7 d of creatine supplementation in normally active older men (59-72 yr) by using a double-blind, placebo-controlled design with repeated measures. After a 3-wk familiarization period to minimize learning effects, a battery of tests was completed on three occasions separated by 7 d (T1, T2, and T3). After T1, subjects were matched and randomly assigned into creatine (N = 10) and placebo (N = 8) groups. After T2, subjects consumed supplements (0.3 g x kg(-1) x d(-1)) for 7 d until T3. All subjects were tested for maximal dynamic strength (one-repetition maximum leg press and bench press), maximal isometric strength (knee extension/flexion), upper- and lower-body explosive power (6 x 10-s sprints on a cycle ergometer), and lower-extremity functional ability (timed sit-stand test and tandem gait test). Body composition was assessed via hydrostatic weighing, and blood samples were obtained to assess renal and hepatic responses and muscle creatine concentrations. RESULTS: No significant increases in any performance measures were observed from T1 to T2 with the exception of isometric right-knee flexion in the placebo group indicating stability in the testing protocols. Significant group-by -time interactions indicated the responses from T2 to T3 were significantly greater (P 相似文献   

Creatine supplementation during resistance training in college football athletes

PURPOSE: This investigation assessed the effects of a 9-wk regimen of creatine monohydrate (Cr x H2O) supplementation coupled with resistance training on body composition and neuromuscular performance in NCAA Division I football athletes. METHODS: Twenty-five subjects were randomly assigned in a double-blind, randomized placebo-controlled design, to a treatment (Cr, N = 9), placebo (P, N = 8), or control group (C, N = 8). The Cr group received 20 g.d(-1) of creatine for the first 5 d in 5-g doses, four times daily, followed by 5 g.d(-1) for the remainder of the study. Each 5-g dose was mixed with 500 mL of glucose solution (Gatorade). The P group received a placebo (sodium phosphate monohydrate; NaH2PO4 x H2O) following the exact protocol as the Cr group. The C group received no supplementation. All subjects resistance trained 4 d.wk(-1). Measurements of neuromuscular performance and body composition were made pre- and post-training after supplementation while monitoring dietary intakes. RESULTS: Repeated measures ANOVA indicated significant differences occurred between the Cr group and the other two groups (P and C) for total body weight, lean body mass, cell hydration, strength, peak torque at 300 degrees.s(-1) knee flexion, percent torque decrement, and anaerobic power and capacity. However, percent body fat, peak torque during both knee flexion and extension at 60 and 180 degrees.s(-1), peak torque at 300 degrees.s(-1) during knee extension, global muscular strength (power clean), and extracellular fluid remained statistically unchanged for all groups. CONCLUSIONS: Our findings indicate that creatine, supplemented concurrently with resistance and anaerobic training, may positively affect cell hydration status and enhance performance variables further than augmentation seen with training alone.     

Once weekly combined resistance and cardiovascular training in healthy older men

PURPOSE: To compare the effects of the 16-wk training period (2 d.wk(-1)) of resistance training alone (S), endurance training alone (E), or combined resistance (once weekly) and endurance (once weekly) training (SE) on muscle mass, maximal strength and power of the leg and arm extensor muscles, and maximal workload (Wmax) by using a incremental cycling test in older men. METHODS: Thirty-one healthy men (65-74 yr) were divided into three treatment groups to train 2x wk(-1) for 16 wk: S (N = 10), E (N = 11), or SE (N = 10; 1x wk(-1) S + 1x wk(-1) E). The subjects were tested at 8-wk intervals (i.e., weeks 8 and 16). RESULTS: There were no significant differences between S- and SE-induced muscle hypertrophy (11% and 11%) and maximal strength (41% and 38%) gains of the legs as well as between E- and SE-induced Wmax (28% and 23%) gains. The increase in arm strength in S (36%) was greater than that recorded in SE (22%) and greater than that recorded in E (0%). CONCLUSIONS: Prolonged combined resistance and endurance training in older men seemed to lead to similar gains in muscle mass, maximal strength, and power of the legs as resistance training alone and to similar gains in maximal peak power output measured in an incremental cycling test as endurance training alone. These findings may have an effect on how resistance exercise is prescribed to older adults.     

Acute creatine supplementation in older men

The hypothesis of this study was that short term creatine (Cr) ingestion in older individuals would increase body mass and exercise performance, as has been shown in younger subjects. Seventeen males 60-78 years old were randomly placed into two groups, Cr and placebo (P), and supplemented in double-blind fashion for 5 days. Subjects ingested either 5 g of Cr plus 1 g of sucrose 4x per day or 6 g of a sucrose placebo 4x per day. Isometric strength of the elbow flexors was assessed using a modified preacher bench attached to a strain gauge. Isokinetic exercise performance was assessed using an intermittent fatigue test of the knee extensors. Subjects performed 3 sets of 30 repetitions with 60 sec rest between sets. There was a small (0.5 kg) but statistically significant increase in body mass (p < 0.05) in the Cr group after supplementation. There was a significant overall interaction between groups in isokinetic performance from pre to post supplementation (group x time x set, p < 0.05). However, analysis of the groups separately revealed that the subjects in the Cr group demonstrated a small non-significant increase in isokinetic performance while subjects in the P group demonstrated a small non-significant performance decrement. There was no significant difference in isometric strength between groups from pre to post supplementation. These data suggest that acute oral Cr supplementation does not increase isometric strength and only produces small increases in isokinetic performance and body mass in men over the age of 60.     

Effects of leg resistance training on arterial function in older men

Background

Little information is available on the effect of strength training on vascular function, particularly in older people.

Objective

To determine the effect of resistance training on arterial stiffness and endothelial function in older adults.

Method

Eleven healthy men (mean (SEM) age 64 (1) years) performed 12 weeks of resistance training involving knee flexion and extension (three sets a day, two days a week).

Results

Resistance training increased maximal muscle power by 16% (p<0.0001). Arterial stiffness as assessed by aortic pulse wave velocity did not change with resistance training. Plasma concentration of nitric oxide (NO), measured as its stable end product (nitrite/nitrate), had increased (p<0.05) after resistance training (61.2 (10.4) v 39.6 (3.2) μmol/l). There was no change in plasma concentration of endothelin‐1.

Conclusion

The results suggest that short term resistance training may increase NO production without stiffening central arteries in healthy older men.     

Progressive resistance training might improve vascular function in older women but not in older men

ObjectivesResistance exercise training increases strength and muscle mass in older adults however there is no consensus for its effect on arterial health. The aim of this study was to determine the effect of community based resistance training versus flexibility training on indicators of arterial stiffness and central blood pressure in healthy older adults and to test whether the effects of training are gender specific.DesignA randomised crossover intervention study.MethodsForty-nine healthy elderly participants (23 males) aged 66.7 ± 4.3 years (mean ± SD) participated in this study which involved undertaking 16 weeks of resistance training and 16 weeks of flexibility training in a random order separated by a four week washout period of usual activity. Prior to and following each training protocol period, participants underwent testing of arterial stiffness as augmentation index; and central blood pressure.ResultsWhen all participants were compared no changes in any measure of arterial stiffness or central blood pressure following resistance training compared to flexibility training were found. When male and female participants were analysed separately, a statistically significant decrease in augmentation index was observed in females (?5.28%; 95% CI: ?10.29 to ?0.26; p = 0.04) but not males (+1.72%; 95% CI: ?3.04 to 6.48; p = 0.48).ConclusionsCommunity based resistance exercise training does not adversely affect vascular function in apparently healthy older adults and may actually improve arterial function in females.     

Mixed-methods resistance training increases power and strength of young and older men

PURPOSE: This study examined the effects of mixed-methods resistance training on young and older men to determine whether similar increases in muscle power were elicited. METHODS: Effects of 10 wk of a periodized resistance-training program designed to increase muscle size, strength, and maximal power on isometric squat strength, time course of force development, muscle fiber characteristics, and muscle activation (iEMG), as well as force and power output during squat jumps, were compared in young (YM, 30 +/- 5 yr, N = 8) and older men (OM, 61 +/- 4 yr, N = 10). RESULTS: Isometric squat strength was higher in the YM compared with OM at all testing occasions and increased over the training period by 23 +/- 15% and 40 +/- 42% for the YM and OM, respectively. The early phase of the force-time curve was shifted upward in both groups over the course of the training. During the squat jumps, the YM produced higher force and power at all test occasions and at all loads tested compared with the OM. The YM increased power output by 15 +/- 14%, 33 +/- 16%, and 26 +/- 12%, and the OM by 7 +/- 5%, 36 +/- 23%, and 25 +/- 16% for the 17 kg, and 30% and 60% 1RM loads, respectively. CONCLUSION: Although the results of this study confirm age-related reductions in muscle strength and power, the older men did demonstrate similar capacity to young men for increases in these variables via an appropriate periodized resistance-training program that includes rapid, high-power exercises.     

Strength training accelerates gastrointestinal transit in middle-aged and older men.

Seven healthy, untrained men (age 60 +/- 2 yr, mean +/- SEM) were studied to determine the effects of a 13-wk total body strength training program on gastrointestinal transit time (GITT). Whole bowel transit time and mouth-to-cecum transit time were assessed before and after the training program. Subjects recorded dietary intake for the 5 d preceding their baseline GITT tests and repeated that diet for 5 d prior to their GITT tests after training. No significant changes in weight or VO2max were observed as a result of the training program. There was a small but significant decrease in body fat assessed by hydrodensitometry (23.4 +/- 2.6% vs 21.8 +/- 2.6%, P less than 0.05). The training program resulted in a 41 +/- 5% increase (P less than 0.001) in upper body strength and a 45 +/- 6% increase (P less than 0.001) in lower body strength. A 38 +/- 6% increase (P less than 0.01) in peak torque of the knee extensors was also observed at 60 degrees.s-1. The training program significantly accelerated whole bowel transit time (41 +/- 11 vs 20 +/- 7 hr; P less than 0.01). There was no significant change in mouth-to-cecum transit time. Thus, a strength training program can accelerate whole bowel transit time in previously sedentary middle-aged and older men. This effect appears to be in the large intestines.     

Effects of resistance training on older adults

Using an integrative approach, this review highlights the benefits of resistance training toward improvements in functional status, health and quality of life among older adults. Sarcopenia (i.e. muscle atrophy) and loss of strength are known to occur with age. While its aetiology is poorly understood, the multifactorial sequelae of sarcopenia are well documented and present a major public health concern to our aging population, as both the quality of life and the likelihood of age-associated declines in health status are influenced. These age-related declines in health include decreased energy expenditure at rest and during exercise, and increased body fat and its accompanying increased dyslipidaemia and reduced insulin sensitivity. Quality of life is affected by reduced strength and endurance and increased difficulty in being physically active. Strength and muscle mass are increased following resistance training in older adults through a poorly understood series of events that appears to involve the recruitment of satellite cells to support hypertrophy of mature myofibres. Muscle quality (strength relative to muscle mass) also increases with resistance training in older adults possibly for a number of reasons, including increased ability to neurally activate motor units and increased high-energy phosphate availability. Resistance training in older adults also increases power, reduces the difficulty of performing daily tasks, enhances energy expenditure and body composition, and promotes participation in spontaneous physical activity. Impairment in strength development may result when aerobic training is added to resistance training but can be avoided with training limited to 3 days/week.     

Enhanced satellite cell proliferation with resistance training in elderly men and women

In addition to the well-documented loss of muscle mass and strength associated with aging, there is evidence for the attenuating effects of aging on the number of satellite cells in human skeletal muscle. The aim of this study was to investigate the response of satellite cells in elderly men and women to 12 weeks of resistance training. Biopsies were collected from the m. vastus lateralis of 13 healthy elderly men and 16 healthy elderly women (mean age 76+/-SD 3 years) before and after the training period. Satellite cells were visualized by immunohistochemical staining of muscle cross-sections with a monoclonal antibody against neural cell adhesion molecule (NCAM) and counterstaining with Mayer's hematoxylin. Compared with the pre-training values, there was a significant increase (P<0.05) in the number of NCAM-positively stained cells per fiber post-training in males (from 0.11+/-0.03 to 0.15+/-0.06; mean+/-SD) and females (from 0.11+/-0.04 to 0.13+/-0.05). These results suggest that 12 weeks of resistance training is effective in enhancing the satellite cell pool in skeletal muscle in the elderly.     

Concurrent cardiovascular and resistance training in healthy older adults

PURPOSE: The recommendations for exercise training and physical activity for older adults include cardiovascular and resistance training components (CVT and RT, respectively). The purpose of the present investigation was to compare the fitness benefits of concurrent CVT and RT with those attained through an equivalent duration of CVT or RT alone. METHODS: Thirty-six participants (ages 60-84) were assigned to a control group or to one of three exercise treatment groups. The treatment groups exercised three times per week for 12 wk using RT (N = 11), CVT (N = 10), or CVT and RT (BOTH, N = 9). Pre- and post-training, participants performed a submaximal exercise test (GXT), five repetition-maximum strength tests (5RM), and the AAHPERD functional fitness test for older adults. RESULTS: All exercise treatment groups revealed lower resting heart rate and rate-pressure product; lower exercise diastolic blood pressure and rating of perceived exertion; increased GXT duration; increased leg, back, and shoulder 5RM scores; and improved AAHPERD flexibility, coordination, and cardiovascular endurance scores. The exercise treatment groups responded differently on the following: RT and BOTH enhanced arm and chest strength more than CVT; and BOTH enhanced AAHPERD strength and agility scores more than CVT or RT. CONCLUSIONS: Concurrent CVT and RT is as effective in eliciting improvements in cardiovascular fitness and 5RM performance as CVT or RT, respectively. Moreover, incorporating both CVT and RT in exercise programs for older adults may be more effective in optimizing aspects of functional fitness than programs that involve only one component.     

Resistance training and intra-abdominal adipose tissue in older men and women

PURPOSE: Little is known concerning the effects of resistance-exercise training (RT) on older adult's intra-abdominal adipose tissue (IAAT). The purpose of this study was to determine the effects of RT on fat distribution in 12 women and 14 men, aged 61-77 yr. METHODS: Computed tomography IAAT and abdominal subcutaneous adipose tissue (SAT), densitometry-determined body composition, one-repetition maximum (1-RM), and isometric strength were measured before and after 25 wk of RT. Training consisted of two sets of 10 repetitions at 65-80% of 1-RM, three times each week. RESULTS: There were similar increases in strength for both the men and women. Women improved 22% and 38% in the isometric strength test and 1-RM test, respectively, whereas the men improved 21% and 36%, respectively. A significant increase in fat-free mass (FFM) was found for both men and women. However, there was a significant gender x time interaction, which indicated that men increased FFM more than women (2.8 kg vs 1.0 kg, respectively). Similar decreases in fat mass (FM) were found for the men (1.8 kg) and women (1.7 kg). However, women lost a significant amount of IAAT (131 to 116 cm2), whereas the men did not (143 to 152 cm2). Similarly, women also lost a significant amount of SAT (254 to 239 cm2), but men did not (165 to 165 cm2). CONCLUSION: Despite similar decreases in FM after a 25-wk RT program, older women lost significant amounts of IAAT and SAT, whereas the older men did not.     

Oxidative stress responses in older men during endurance training and detraining

PURPOSE: Aging is associated with increased oxidative stress, whereas systematic exercise training has been shown to improve quality of life and functional performance of the aged. This study aimed to evaluate responses of selected markers of oxidative stress and antioxidant status in inactive older men during endurance training and detraining. METHODS: Nineteen older men (65-78 yr) were randomly assigned into either a control (C, N = 8) or an endurance-training (ET, N = 11, three training sessions per week, 16 wk, walking/jogging at 50-80% of HR(max)) group. Before, immediately posttraining, and after 4 months of detraining, subjects performed a progressive diagnostic treadmill test to exhaustion (GXT). Plasma samples, collected before and immediately post-GXT, were analyzed for malondialdehyde (MDA) and 3-nitrotyrosine (3-NT) levels, total antioxidant capacity (TAC), and glutathione peroxidase activity (GPX). RESULTS: ET caused a 40% increase in running time and a 20% increase in maximal oxygen consumption (VO(2max)) (P < 0.05). ET lowered MDA (9% at rest, P < 0.01; and 16% postexercise, P < 0.05) and 3-NT levels (20% postexercise, P < 0.05), whereas it increased TAC (6% at rest, P < 0.01; and 14% postexercise, P < 0.05) and GPX (12% postexercise, P < 0.05). However, detraining abolished these adaptations. CONCLUSIONS: ET may attenuate basal and exercise-induced lipid peroxidation and increase protection against oxidative stress by increasing TAC and GPX activity. However, training cessation may reverse these training-induced adaptations.     

Creatine supplementation and sprint performance in soccer players

PURPOSE: This investigation examined the effects of creatine (Cr) supplementation on intermittent high-intensity exercise activities specific to competitive soccer. METHODS: On two occasions 7 d apart, 17 highly trained male soccer players performed a counter-movement jump test (CMJT), a repeated sprint test (RST) consisting of six maximal 15-m runs with a 30-s recovery, an intermittent endurance test (IET) consisting of forty 15-s bouts of high-intensity running interspersed by 10-s bouts of low-intensity running, and a recovery CMJT consisting of three jumps. After the initial testing session, players were evenly and randomly included in a CREATINE (5 g of Cr, four times per day for 6 d) or a PLACEBO group (same dosage of maltodextrins) using a double-blind research design. RESULTS: The CREATINE group's average 5-m and 15-m times during the RST were consistently faster after the intervention (0.95 +/- 0.03 vs 0.97 +/- 0.02 s, P < 0.05 and 2.29 +/- 0.08 vs 2.32 +/- 0.07 s, P = 0.07, respectively). Neither group showed significant changes in the CMJT or the IET. The CREATINE group's recovery CMJT performance relative to the resting CMJT remained unchanged postsupplementation, whereas it tended to decrease in the PLACEBO group. CONCLUSION: In conclusion, acute Cr supplementation favorably affected repeated sprint performance and limited the decay in jumping ability after the IET in highly trained soccer players. Intermittent endurance performance was not affected by Cr.     

Creatine supplementation improves sprint performance in male sprinters

The object of this study was to evaluate the effect of creatine (Cr) supplementation in well trained male sprinters. The study was performed as a single blind test on 18 sprinters at a local competition level. During the last two years a substantial part of their training had consisted of a series of maximal sprints with short rest periods to improve their fatigue resistance. The participants consumed either 20 g Cr+20 g glucose per day (Cr group, n=9) or 40 g glucose per day (placebo group, n=9), divided into 4 equal dosages. The effect of Cr on sprint performance was evaluated in two tests, 1 x 100 m sprint and an intermittent 6x60 m sprint. Cr supplementation increased the 100 m sprint velocity (11.68+/-0.27 s vs 11.59+/-0.31 s) and reduced the total time of 6 intermittent 60 m sprints (45.63+/-1.11 s vs 45.12+/-1.1 s), whereas no changes were observed in the placebo group. The sprint velocity was significantly increased in 5 out of 6 intermittent 60 m sprints. Venous blood was drawn 5 min after finishing the final intermittent 60 m run. Plasma lactate, Cr and serum creatinine (Crn) were all increased in the Cr group compared to presupplementation values; no changes were observed in the placebo group. The improved sprint performance suggests an increased availability of energy substrate for performing work, possibly as a result of increased skeletal muscle creatine phosphate (PCr).     

Performance and muscle fiber adaptations to creatine supplementation and heavy resistance training.

PURPOSE: The purpose of this study was to examine the effect of creatine supplementation in conjunction with resistance training on physiological adaptations including muscle fiber hypertrophy and muscle creatine accumulation. METHODS: Nineteen healthy resistance-trained men were matched and then randomly assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N = 9) group. Periodized heavy resistance training was performed for 12 wk. Creatine or placebo capsules were consumed (25 g x d(-1)) for 1 wk followed by a maintenance dose (5 g x d(-1)) for the remainder of the training. RESULTS: After 12 wk, significant (P < or = 0.05) increases in body mass and fat-free mass were greater in creatine (6.3% and 6.3%, respectively) than placebo (3.6% and 3.1%, respectively) subjects. After 12 wk, increases in bench press and squat were greater in creatine (24% and 32%, respectively) than placebo (16% and 24%, respectively) subjects. Compared with placebo subjects, creatine subjects demonstrated significantly greater increases in Type I (35% vs 11%), IIA (36% vs 15%), and IIAB (35% vs 6%) muscle fiber cross-sectional areas. Muscle total creatine concentrations were unchanged in placebo subjects. Muscle creatine was significantly elevated after 1 wk in creatine subjects (22%), and values remained significantly greater than placebo subjects after 12 wk. Average volume lifted in the bench press during training was significantly greater in creatine subjects during weeks 5-8. No negative side effects to the supplementation were reported. CONCLUSION: Creatine supplementation enhanced fat-free mass, physical performance, and muscle morphology in response to heavy resistance training, presumably mediated via higher quality training sessions.     

Comparison of strength development with resistance training and combined exercise training in type 2 diabetes

Resistance training has been shown to increase strength in type 2 diabetes; however, it is unclear if combining resistance and aerobic training (A + R) impedes strength development compared with resistance training only (R). The purpose of this study was to compare changes in strength with A + R vs R in individuals with type 2 diabetes. We evaluated monthly workload increments in participants from the Diabetes Aerobic and Resistance Exercise clinical trial. Muscular strength was assessed through training volumes and as the eight repetition maximum (8‐RM) at 0, 3, and 6 months. Both groups increased their upper and lower body volumes monthly for 6 months. The relative increase in upper body workload in R was significantly greater than A + R at 4 months (161 ± 11% vs 127 ± 11%, P = 0.009) and at 6 months of training (177 ± 11% vs 132 ± 11%, P = 0.008). Both groups had improvements in 8‐RM workloads at 3 and 6 months. The resistance training group had a significantly greater improvement in 8‐RM on the leg press at 6 months compared with A + R (80 ± 11% vs 58 ± 8%, P = 0.045). Both R and A + R improved strength with a 6‐month training program; however, increases in strength may be greater with resistance training alone compared with performing both aerobic and resistance training.