Increase Muscle Endurance Research Articles

Exercise for Better ALS Management?

Exercise for Better ALS Management?

Effects of training interventions prior to thoracic or abdominal surgery: a systematic review

Introduction: Developments in the areas of anaesthesia, analgesia, and pre- and postoperative care have decreased the risk of postoperative pulmonary complications (PPCs) after abdominal and thoracic surgery. Preoperative educational and training interventions to optimize patient status may further reduce these risks.Objectives: To evaluate the level of evidence for educational and training interventions before abdominal and thoracic surgery.Methods: A literature search for clinical studies evaluating effects of different educational and training interventions in adults before major, open abdominal or thoracic surgery was done in the following databases: MEDLINE/PubMed, CINAHL, PEDro, and Cochrane. Reference lists of articles that were identified were searched for additional relevant studies. All searches were limited to full-length articles written in English. Published trials evaluating preoperative treatment postoperatively were included. The randomized controlled trials were evaluated concerning their internal validity and the degree of evidence for different interventions was set.Results: Nineteen articles were included. The results indicated that there were: no evidence that preoperative information or general or deep breathing exercises before admission were effective in preventing PPC, a low degree of evidence that preoperative pulmonary rehabilitation was effective in preventing PPC, increasing peak expiratory flow, and shortening ventilation time and the hospital stay, a moderate degree of evidence that inspiratory muscle training (IMT) increased muscle endurance, and a low degree of evidence that IMT decreased PPC and shortened hospital stay.Conclusion: There is currently evidence that pulmonary rehabilitation and breathing exercises including IMT are effective in preventing PPC and should therefore be considered in clinical practice.

Phototherapy and Grip Muscle Performance

Background: Grip strength and endurance has been shown to be an overall indicator of physical strength, function, and health. Previous research has provided evidence that phototherapy may increase muscle endurance. The purpose of this study was to investigate the effects of red/infrared light and blue/infrared light on grip endurance, lactic acid accumulation, and delayed onset muscle soreness (DOMS). Materials and Methods: Fourteen subjects, seven men, and seven women (mean age 23.2 ± 1.7) took part in this randomized crossover double-blinded study. The subjects received either phototherapy (red/infrared probe with 4 red light emitting diodes (LEDs); λ= 670nm; 5 infrared laser diodes; λ= 850nm; 540mW power output; 65 seconds of irradiation, applied in 3 locations over the forearm and hand of the dominant arm; 35.1 J of total energy per site), phototherapy (blue/infrared probe with 28 blue LEDs emitting λ= 405nm; 8 infrared LEDs emitting λ= 880nm; 500mW of power output; 80 seconds, applied to the same points for a 40.0 J total energy per site) or placebo phototherapy using an identical cluster probe. The dosage in energy density units for the phototherapy treatments were 8 J/cm2 per site. Each intervention was applied immediately before performance of the grip endurance exercise. All subjects performed voluntary grip strength repetitions until they reached 50% of their initial maximal voluntary contraction. The number of repetitions performed was utilized for data analysis. Lactic acid (La) accumulation was measured five minutes after the exercise has been completed. A visual pain analog scale measured DOMS at 24 and 48 hours post exercise. Results: There were no significant differences between any of the three conditions on muscle endurance, La accumulation and pain scores as analyzed by Repeated Measures ANOVA. Conclusion: The application of a standard therapeutic dosage of phototherapy did not improve grip endurance.

EFFECTS OF LONG-TERM CORSET WEARING ON CHRONIC LOW BACK PAIN

There are few studies of the therapeutic effects of long-term corset wearing in patients with chronic low back pain. The aim of this study was to evaluate the effects of long-term corset wearing on chronic low back pain and to examine the myoelectrical activities of the paravertebral muscles. Forty subjects with chronic low back pain were enrolled and randomly divided into two groups: a group wearing corsets for 6 months (CW) group and a group not wearing corsets (NW). The treatment effects were measured using the Japanese Orthopaedic Association (JOA) score. Muscle endurance was evaluated during the Biering-Sorensen test (S-test), and the degree of muscle fatigue was evaluated by the change in percent mean power frequency (%MPF) of the paravertebral muscles. Corset treatment for chronic low back pain improved low back pain and increased muscle endurance for a short period of time. Paravertebral muscle fatigue was not increased by long-term corset wearing for chronic low back pain, and weakening of the paravertebral muscles was not observed up to 6 months after the start of corset wearing.

Evaluation of in Vivo Rotator Cuff Muscle Function After Acute and Chronic Detachment of the Supraspinatus Tendon

Surgical repair of large chronic rotator cuff tears can be technically demanding because it requires manipulation of a muscle-tendon unit that is scarred, retracted, and stiffer than normal, all of which contribute to increased tension at the repair site. The purpose of the present study was to characterize the in vivo rotator cuff muscle-tendon unit function after acute and chronic injury at surgically relevant preload tensions. Sixty-two Sprague-Dawley rats were divided into a healthy, uninjured (control) group (n = 22), an acute injury group (n = 20), and a chronic injury group (n = 20) and underwent in vivo muscle force testing and electromyographic testing of the supraspinatus muscle-tendon unit at various preload tensions. Preload tension affected the maximum supraspinatus muscle contractile force in all groups (p < 0.05). At the peak tension required to repair an acute tear, there was a 28% to 30% reduction in maximum tetanic contraction amplitude in all groups (p < 0.05). At the peak tension required to repair a chronic tear, there was a 40% to 53% reduction in maximal tetanic contraction amplitude in all groups (p < 0.05). The uninjured (control) group showed increased muscle endurance (p < 0.05) in comparison with the acute injury and chronic injury groups at all preload tensions. The chronic injury group showed reduced compound motor action potential amplitude (p < 0.05). Both the acute and chronic injury groups demonstrated functional impairment related to increasing preload tensions. Higher repair tensions, associated with the chronic injury setting, resulted in greater functional impairment. The present study also demonstrates an association between increased time from rotator cuff tendon injury and impaired in vivo rotator cuff muscle electromyographic findings.

Progressive resistance training did not improve walking but can improve muscle performance, quality of life and fatigue in adults with multiple sclerosis: a randomized controlled trial

Background: Few high-quality trials have examined the effects of progressive resistance training (PRT) on people with multiple sclerosis (MS). Objective: To determine the effectiveness of PRT for people with MS, focusing on improving the gait deficits common in this population. Methods: Using a single blind randomized controlled trial, people with relapsing–remitting MS were randomly allocated to either a PRT program targeting the lower limb muscles twice a week for 10 weeks (n = 36), or usual care plus an attention and social program conducted once a week for 10 weeks (n = 35). Outcomes were recorded at baseline, week 10 and week 22. Results: Participants attended 92% of training sessions, with no serious adverse events. At 10 weeks, no differences were detected in walking performance. However, compared with the comparison group PRT demonstrated increased leg press strength (16.8%, SD 4.5), increased reverse leg press strength (29.8%, SD 12.7), and increased muscle endurance of the reverse leg press (38.7%, SD 32.8). Improvements in favor of PRT were also found for physical fatigue (Mean difference −3.9 units, 95%CI −6.6 to −1.3), and the physical health domain of quality of life (Mean difference 1.5 units, 95%CI 0.1 to 2.9). At week 22 almost no between-group differences remained. Conclusion: PRT is a relatively safe intervention that can have short-term effects on reducing physical fatigue, increasing muscle endurance and can lead to small improvements in muscle strength and quality of life in people with relapsing–remitting MS. However, no improvements in walking performance were observed and benefits do not appear to persist if training is completely stopped.

Incidência e características das lesões em praticantes de kitesurf. DOI: 10.5007/1980-0037.2011v13n3p195

Kitesurfing is a new sport and consists of a combination of surf, windsurf and wakeboard. Its main characteristics are the relationship with wind speed and direction and the high rate of injuries. The aim of this study was to determine the type, body region, and etiological agent of injuries in kitesurfers from the towns of Pelotas and Rio Grande, RS. A sample of 50 kitesurfers (mean age: 30.7 ± 7.9 years, height: 175.9 ± 6.6 cm, body weight: 79.4 ± 11.5 kg, and practice time: 4.2 ± 2.7 years) was studied. A questionnaire with open and closed questions was used for data collection. Seventy-three injuries were identified in all participants and most of them had more than one type of injury. Sprain was the most frequent type of injury (35.6%) and the lower limbs were the most affected (50.7%). The maneuver was the etiological agent that caused most injuries (57.5%). This study suggests proprioceptive exercise to increase the power of muscle recruitment in extreme situations; stretch training especially of the trunk and lower limbs, the sites most affected by injuries, and global workout to increase muscle endurance.

Chronic hypoxia increases rat diaphragm muscle endurance and sodium-potassium ATPase pump content

The effects of chronic hypoxia (CH) on respiratory muscle are poorly understood. The aim of the present study was to examine the effects of CH on respiratory muscle structure and function, and to determine whether nitric oxide is implicated in respiratory muscle adaptation to CH. Male Wistar rats were exposed to CH for 1-6 weeks. Sternohyoid and diaphragm muscle contractile properties, muscle fibre type and size, the density of fibres expressing sarco/endoplasmic reticulum calcium-ATPase (SERCA) 2 and sodium-potassium ATPase (Na+,K+-ATPase) pump content were determined. Muscle succinate dehydrogenase (SDH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) dehydrogenase activities were also assessed. Acute and chronic blockade of nitric oxide synthase (NOS) was employed to determine whether or not NO is critically involved in functional remodelling in CH muscles. CH improved diaphragm, but not sternohyoid, fatigue tolerance in a time-dependent fashion. This adaptation was not attributable to increased SDH or NADPH dehydrogenase activities. The areal density of muscle fibres and relative area of fibres expressing SERCA2 were unchanged. Na+,K+-ATPase pump content was significantly increased in CH diaphragm. Chronic NOS inhibition decreased diaphragm Na+,K+-ATPase pump content and prevented CH-induced increase in muscle endurance. This study provides novel insight into the mechanisms involved in CH-induced muscle plasticity. The results may be of relevance to respiratory disorders characterised by CH, such as chronic obstructive pulmonary disease.

Distributed low‐frequency functional electrical stimulation delays muscle fatigue compared to conventional stimulation

We present a low-frequency stimulation method via multi-pad electrodes for delaying muscle fatigue. We compared two protocols for muscle activation of the quadriceps in paraplegics. One protocol involved a large cathode at 30 HZ (HPR, high pulse-rate), and the other involved four smaller cathodes at 16 HZ (LPR, low pulse-rate). The treatment included 30-min daily sessions for 20 days. One leg was treated with the HPR protocol and the other with the LPR protocol. Knee-joint torque was measured before and after therapy to assess the time interval before the knee-joint torque decreased to 70% of the initial value. The HPR therapy provided greater increases in muscle endurance and force in prolonged training. Yet the LPR stimulation produced less muscle fatigue compared to the HPR stimulation. The results suggest that HPR is the favored protocol for training, and LPR is better suited for prolonged stimulation.

The Effect of a Structured Exercise Program on Nutrition and Fitness Outcomes in Human Immunodeficiency Virus-Infected Children

The feasibility and effectiveness of a hospital-based exercise-training program followed by a home-based program for improving fitness, strength, and changes in body composition in children and adolescents with HIV were evaluated. Subjects participated in nonrandomized 24-session, hospital supervised exercise training program followed by an 314 unsupervised home-based maintenance program. Outcome measurements included muscular strength/endurance, flexibility, relative peak VO(2), body composition, and lipids. Seventeen subjects (eight females) with a median age of 15.0 years (range: 6.0-22.6) and BMI z-score of 0.61 (range: -1.70-2.57) at entry completed the intervention. After 24 training sessions, the median increases in muscular strength were between 8% and 50%, depending on muscle group. The median increases in muscle endurance, relative peak VO(2), and lean body mass were 38.7% (95% CI: 12.5-94.7; p = 0.006), 3.0 ml/kg/min (95% CI: 1.5-6.0; p < 0.001), and 4.5% (95% CI: 2.4-6.6; p < 0.001), respectively. Twelve children completed the home-based maintenance program. Median changes in these outcomes between completion of the hospital-based intervention and a follow-up after completion of the home-based program were near zero. No adverse events occurred during the intervention. A supervised hospital-based fitness program is feasible, safe, and effective for improving general fitness and strength as well as lean body mass in children with HIV.

Muscle Stimulation Waveform Timing Patterns for Upper and Lower Leg Muscle Groups to Increase Muscular Endurance in Functional Electrical Stimulation Pedaling Using a Forward Dynamic Model

Functional electrical stimulation (FES) of pedaling provides a means by which individuals with spinal cord injury can obtain cardiorespiratory exercise. However, the early onset of muscle fatigue is a limiting factor in the cardiorespiratory exercise obtained while pedaling an FES ergometer. One objective of this study was to determine muscle excitation timing patterns to increase muscle endurance in FES pedaling for three upper leg muscle groups and to compare these timing patterns to those used in a commercially available FES ergometer. The second objective was to determine excitation timing patterns for a lower leg muscle group in conjunction with the three upper leg muscle groups. The final objective was to determine the mechanical energy contributions of each of the muscle groups to drive the crank. To fulfill these objectives, we developed a forward dynamic simulation of FES pedaling to determine electrical stimulation on and off times that minimize the muscle stress-time integral of the stimulated muscles. The computed electrical stimulation on and off times differed from those utilized by a commercially available FES ergometer and resulted in 17% and 11% decrease in the muscle stress-time integral for the three upper leg muscle groups and four upper and lower leg muscle groups, respectively. Also, the duration of muscle activation by the hamstrings increased by 5% over a crank cycle for the computed stimulation on and off times, and the mechanical energy generated by the hamstrings increased by 20%. The lower leg muscle group did not generate sufficient mechanical energy to reduce the energy contributions of the upper leg muscle groups. The computed stimulation on and off times could prolong FES pedaling, and thereby provide improved cardiorespiratory and muscle training outcomes for individuals with spinal cord injury. Including the lower leg muscle group in FES pedaling could increase cardiorespiratory demand while not affecting the endurance of the muscles involved in the pedaling task.

Effect of resistance training on strength and endurance of muscle in chronic heart failure

Resistance training (RT) has been used to increase muscle strength and endurance. In CHF patients, the effect of RT has not been thoroughly investigated. This study was conducted to explore the effect of RT to reverse muscular weaknesses and decreased muscular endurance that have been found in many CHF patients. A prospective-randomized controlled study was used as the research design. The effect of RT on muscular strength and endurance was evaluated in 39 CHF patients with II-III New York Heart Association (NYHA) functional class and left ventricle ejection fraction (LVEF), 27 + 7 (mean + standard deviation) in the exercise group and 28 + 6 in the control group. Initial two tests, knee extensor/flexor and elbow extensor/flexor for measuring strength and endurance were performed one week apart using isokinetic machine. After randomization (exercise group=EG and control group=CG), EG performed 3 months supervised RT in hydraulic machine using incremental approach based on individual response. All patients followed the end-point test. The result showed that muscular strength and endurance in EG increased by 20 + 19% (p <.000) and 25 + 26% (p < .001), respectively while in the CG, strength and endurance nearly unchanged. The difference between groups was significant (p< .006 for strength and p < .003 for endurance). There was no adverse cardiac event occurred during the test and training sessions. In conclusion, resistance training was safe for stable CHF patients and was able to increase muscular strength and endurance.

An Actn3 knockout mouse provides mechanistic insights into the association between -actinin-3 deficiency and human athletic performance

A common nonsense polymorphism (R577X) in the ACTN3 gene results in complete deficiency of the fast skeletal muscle fiber protein alpha-actinin-3 in an estimated one billion humans worldwide. The XX null genotype is under-represented in elite sprint athletes, associated with reduced muscle strength and sprint performance in non-athletes, and is over-represented in endurance athletes, suggesting that alpha-actinin-3 deficiency increases muscle endurance at the cost of power generation. Here we report that muscle from Actn3 knockout mice displays reduced force generation, consistent with results from human association studies. Detailed analysis of knockout mouse muscle reveals reduced fast fiber diameter, increased activity of multiple enzymes in the aerobic metabolic pathway, altered contractile properties, and enhanced recovery from fatigue, suggesting a shift in the properties of fast fibers towards those characteristic of slow fibers. These findings provide the first mechanistic explanation for the reported associations between R577X and human athletic performance and muscle function.

UTILITY OF THE POWERBALL® IN THE INVIGORATION OF THE MUSCULATURE OF THE FOREARM

In order to ascertain the utility of a 250 Hz NSD Powerball gyroscope in increasing the maximum grip force and muscular endurance of the forearm, ten adults without pathology in their upper limbs exercised one forearm with the device during a period of one month. We evaluated grip strength and forearm muscle endurance with a Jamar dynamometer both at the end of the month as well as after a resting period of one month. There was a tendency (not statistically significant p = 0.054), for the volunteers to increase their maximum grip strength. There was also highly significant increase in muscle endurance (p = 0.00001), a gain that remained slightly unchanged after the rest. Because the gyroscope generates random multidirectional forces to the forearm, the reactive muscle contraction is likely to stimulate more efficient neuromuscular contro of the wrist, a conclusion which our work appears to validate. The use of Powerball in forearm proprioception deficient patients is, therefore, justified.

Aspartate as an Ergogenic Supplement

Aspartate has been regularly listed in exercise physiology textbooks as an ergogenic substance since the first known trial by Professor Henri Laborit's laboratory in the late 1950s, aimed at verifying its ergogenic potential. The main outcomes of aspartate supplementation are attenuation of exercise-induced hyperammonaemia and increase of exercise endurance. In the available literature, the impact of aspartate on endurance seems generally favourable in humans, but it is not so favourable in experimental animals. In studies reporting increased endurance, no correlation has been found between its dosage and the increment of exercise time. Mechanisms supposed to explain the ergogenic effect of aspartate have also been reviewed in this article. Claims of a glycogen-sparing action, reduced hyperammonaemia and a higher rate of free fatty acid oxidation have not been confirmed unequivocally by the literature. Aspartate has not been shown to increase muscle endurance or strength. It is often used in combinations that are briefly reviewed in this article. However, the number of studies are presently too low to draw conclusions about the efficacy of these aspartate combinations. Furthermore, as in most studies on supplements, including aspartate alone or in combination, it is difficult to exclude a potential publication bias against non-significant results.

Improved isometric force endurance after transcranial direct current stimulation over the human motor cortical areas

Neuromuscular fatigue is the exercise-dependent decrease in the ability of muscle fibres to generate force. To investigate whether manipulation of brain excitability by transcranial direct current stimulation (tDCS; 1.5 mA, 10 min, 0.026 C/cm(2)) modulates neuromuscular fatigue, we evaluated the effect of brain polarization over the right motor areas of the cerebral cortex of healthy subjects on the endurance time for a submaximal isometric contraction of left elbow flexors. In 24 healthy volunteers the study protocol comprised an assessment of the maximum voluntary contraction (MVC) for the left elbow flexors and a fatiguing isometric contraction (35% of MVC), before and immediately after brain polarization. One hour elapsed between baseline (T0) and postconditioning (T1) evaluation. After tDCS, MVC remained unchanged from baseline (mean +/- SEM; anodal tDCS: T0, 154.4 +/- 18.07; T1, 142.8 +/- 16.62 N; cathodal tDCS: T0, 156 +/- 18.75; T1, 141.86 +/- 17.53 N; controls: T0, 148.8 +/- 6.64; T1, 137.6 +/- 7.36 N; P > 0.1). Conversely, endurance time decreased significantly less after anodal than after cathodal tDCS or no stimulation (-21.1 +/- 5.5%, -35.7 +/- 3.3% and -39.3 +/- 3.3%, respectively; P < 0.05). None of the evaluated electromyographic variables changed after tDCS. Anodal tDCS could improve endurance time by directly modulating motor cortical excitability, modulating premotor areas, decreasing fatigue-related muscle pain, increasing motivation and improving synergist muscle coupling. Our findings, showing that anodal tDCS over the motor areas of the cerebral cortex improves muscle endurance, open the way to increasing muscle endurance and decreasing muscle fatigue in normal (i.e. sports medicine) and pathological conditions.

Progressive resistance exercise for people with multiple sclerosis

Purpose. This study aimed to determine if participation in a progressive resistance exercise (PRE) programme can: (1) increase the ability to generate maximal muscle force, (2) increase muscle endurance, (3) increase functional activity, and (4) improve overall psychological function of people with multiple sclerosis (MS).Methods. A pre-post single group research design with a 4-week baseline familiarisation phase was used. Nine people (mean age 45.6 years, SD 10.7) with MS attended a gymnasium three times over 4 weeks for familiarization. Participants then completed a twice-weekly 10-week PRE programme, with two sets of 10 – 12 repetitions of each exercise. Outcome measures of muscle strength (1RM for arms and legs), muscle endurance (repetitions at half 1RM), walking speed, the 2-min walk test (2MWT), a timed stairs test, and the impact of MS on physical and psychological function were taken at weeks 2, 4, and 14.Results. Participants attended 94.3% (SD 8.2%) of the training sessions, with no adverse events. After accounting for baseline stability, significant improvements (P < 0.05) were found in arm strength (14.4%), leg endurance (170.9%), fast walking speed (6.1%), and there was a trend for increased distance in the 2MWT (P = 0.06). The perceived impact of MS on physical function was reduced (P = 0.02).Conclusions. Adults with MS benefited from a PRE programme by improving muscle performance and physical activities, without adverse events. These findings suggest that PRE may be a feasible and useful fitness alternative for people with mild to moderate disability due to MS.

Chapter 3 Electrical stimulation for therapy and mobility after spinal cord injury

This article reviews the use of therapeutic and functional electrical stimulation in subjects after a spinal cord injury (SCI). Muscles become much weaker and more fatigable, while bone density decreases dramatically after SCI. Therapeutic stimulation of paralyzed muscles for about 1 h/day can reverse the atrophic changes and markedly increase muscle strength and endurance as well as bone density. Functional electrical stimulation can also improve the speed and efficiency of walking in people with an incomplete SCI. Finally, a modified wheelchair is described in which electrical stimulation or residual voluntary activation of leg muscles can produce movements of a footrest that is coupled to the wheels. The wheelchair can provide greater mobility and fitness to persons who are not functional walkers and currently use their arms to propel a wheelchair.

Fast-to-slow conversion following chronic low-frequency activation of medial gastrocnemius muscle in cats. I. Muscle and motor unit properties.

This study of cat medial gastrocnemius (MG) muscle and motor unit (MU) properties tests the hypothesis that the normal ranges of MU contractile force, endurance, and speed are directly associated with the amount of neuromuscular activity normally experienced by each MU. We synchronously activated all MUs in the MG muscle with the same activity (20 Hz in a 50% duty cycle) and asked whether conversion of whole muscle contractile properties is associated with loss of the normal heterogeneity in MU properties. Chronically implanted cuff electrodes on the nerve to MG muscle were used for 24-h/day stimulation and for monitoring progressive changes in contractile force, endurance, and speed by periodic recording of maximal isometric twitch and tetanic contractions under halothane anesthesia. Chronic low-frequency stimulation slowed muscle contractions and made them weaker, and increased muscle endurance. The most rapid and least variable response to stimulation was a decline in force output of the muscle and constituent MUs. Fatigue resistance increased more slowly, whereas the increase in time to peak force varied most widely between animals and occurred with a longer time course than either force or endurance. Changes in contractile force, endurance, and speed of the whole MG muscle accurately reflected changes in the properties of the constituent MUs both in extent and time course. Normally there is a 100-fold range in tetanic force and a 10-fold range in fatigue indexes and twitch time to peak force. After chronic stimulation, the range in these properties was significantly reduced and, even in MU samples from single animals, the range was shown to correspond with the slow (type S) MUs of the normal MG. In no case was the range reduced to less than the type S range. The same results were obtained when the same chronic stimulation pattern of 20 Hz/50% duty cycle was imposed on paralyzed muscles after hemisection and unilateral deafferentation. The findings that the properties of MUs still varied within the normal range of type S MUs and were still heterogeneous despite a decline in the variance in any one property indicate that the neuromuscular activity can account only in part for the wide range of muscle properties. It is concluded that the normal range of properties within MU types reflects an intrinsic regulation of properties in the multinucleated muscle fibers.

Tissue Distribution of (8&lt;sub&gt;-&lt;/sub&gt;&lt;sup&gt;14&lt;/sup&gt;C)&lt;sub&gt;-&lt;/sub&gt;Octacosanol in Liver and Muscle of Rats after Serial Administration

The present study investigates the metabolic disposition of octacosanol in liver and muscle of rats after serial doses administration. Three groups of experimental animals received various doses of (8-14C)-octacosanol (2.0 microCi/dose) orally through a stomach tube. When expressed per organ, the highest amount of radioactivity was found in the liver (9.5% of administered dose), followed by the digestive tracts (8.2%) and the muscle (3.5%) at all doses of administration. The radioactivity in all other tissues examined was insignificant (< 0.9% in each) at any time during this period. The radioactivity in liver disappeared rapidly after 2-dose administration, even when the doses were increased. In contrast, the muscle seemed to be able to store a considerable amount of octacosanol in response to doses of administration. In case of 9-dose serial administration, after 3 and 9 days the accumulation of radioactivity in muscle was higher than that of the liver, possibly due to slow elimination of radioactivity from muscle. By the time when radioactivity in liver and muscle was low (after 6 and 10 doses), the radioactivity of octacosanol in plasma reached a maximum, particularly after administration of 6 doses. The plasma concentration and the fecal excretion of the radioactivity of octacosanol reached a maximum at the third day after the oral 6 doses, which reflected not only the saturation of radioactivity uptake by liver and muscle but also the metabolism and excretion of octacosanol with time at the same period. The results are discussed in the light of the role of octacosanol in increasing muscle endurance in exercise.