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We have evaluated changes in the expression of neurotrophin-3 (NT-3) and its tyrosine kinase C (TrkC) receptor in the neuromuscular system as a result of voluntary physical activity. We assessed changes in the mRNAs and proteins for NT-3 and TrkC in the lumbar spinal cord and associated soleus muscle following 3 and 7 days of voluntary wheel running. We used quantitative Taqman RT-PCR to measure mRNA and ELISA to assess protein levels. NT-3 mRNA and protein levels increased in the spinal cord to reach statistical significance after 7 days of exercise compared to sedentary control rats. Immunohistochemical analyses localized the elevated NT-3 to the substantia gelatinosa (SG) and nucleus of the dorsal horn. TrkC mRNA levels were significantly elevated in the spinal cord after 3 and 7 days of running. In the soleus muscle, NT-3 mRNA levels and its receptor TrkC were elevated after 3 days, while NT-3 protein levels remained unaffected. The results demonstrate that voluntary exercise has a differential effect on NT-3 as well as its receptor TrkC in the neural and muscular components of the neuromuscular system, and emphasize the role of voluntary activity on the spinal cord and muscle.

We have investigated potential mechanisms by which exercise can promote changes in neuronal plasticity via modulation of neurotrophins. Rodents were exposed to voluntary wheel running for 3 or 7 days, and their lumbar spinal cord and soleus muscle were assessed for changes in brain-derived neurotrophic factor (BDNF), its signal transduction receptor (trkB), and downstream effectors for the action of BDNF on synaptic plasticity. Exercise increased the expression of BDNF and its receptor, synapsin I (mRNA and phosphorylated protein), growth-associated protein (GAP-43) mRNA, and cyclic AMP response element-binding (CREB) mRNA in the lumbar spinal cord. Synapsin I, a synaptic mediator for the action of BDNF on neurotransmitter release, increased in proportion to GAP-43 and trkB mRNA levels. CREB mRNA levels increased in proportion to BDNF mRNA levels. In separate experiments, the soleus muscle was paralyzed unilaterally via intramuscular botulinum toxin type A (BTX-A) injection to determine the effects of reducing the neuromechanical output of a single muscle on the neurotrophin response to motor activity. In sedentary BTX-A-treated rats, BDNF and synapsin I mRNAs were reduced below control levels in the spinal cord and soleus muscle. Exercise did not change the BDNF mRNA levels in the spinal cord of BTX-A-treated rats but further reduced the BDNF mRNA levels in the paralyzed soleus relative to the levels in sedentary BTX-A-treated rats. Exercise also restored synapsin I to near control levels in the spinal cord. These results indicate that basal levels of neuromuscular activity are required to maintain normal levels of BDNF in the neuromuscular system and the potential for neuroplasticity.

The purpose of the present study was to compare the myogenic response of hindlimb muscles in young (14-20 wk of age) and old (>120 wk of age) rats with a single exhaustive bout of heavy resistance weight lifting. [(3)H]thymidine and [(14)C]leucine labeling were monitored for up to 2 wk after the exercise bout to estimate serial changes in mitotic activity and the level of amino acid uptake and myosin synthesis. Histological, histochemical, and immunohistochemical [anti-5-bromo-2'-deoxyuridine and myogenic determination genes (MyoD)] analyses of whole muscles and analysis of muscle-specific gene expression (MyoD) using Western blotting and RT-PCR were performed. Old rats showed significant muscle atrophy and a lower exercise capacity than young rats. Exercise-induced muscle damage, as assessed in histological sections, and increases in serum creatine kinase activity were evident in both young and old exercised groups. Mitotic activity was increased in young, but not old, rats 2 days after exercise. There was a biphasic increase in [(14)C]leucine uptake during the 14 days postexercise (peaks at 1-4 and 10 days) in young rats: only the first peak was observed in old rats. There was a lower uptake of [(14)C]leucine in the myosin fraction and an impaired expression of MyoD at the protein (immunohistochemistry and Western blotting) and mRNA (RT-PCR) levels in old rats throughout the postexercise period. These results demonstrate a reduced reparative capability of muscle in response to a single bout of exercise in old compared with young rats.

There have been no systematic comparisons of skeletal muscle adaptations in response to voluntary wheel running under controlled loading conditions. To accomplish this, a voluntary running wheel for rats and mice was developed in which a known load can be controlled and monitored electronically. Five-week-old male Sprague-Dawley rats (10 rats/group) were assigned randomly to either a 1) sedentary control group (Control); 2) voluntary exercised with no load (Run-No-Load) group; or 3) voluntary exercised with additional load (Run-Load) group for 8 wk. The load for the Run-Load group was progressively increased to reach approximately 60% of body weight during the last week of training. The proportions of fast glycolytic (FG), fast oxidative glycolytic (FOG), or slow oxidative (SO) fibers in the plantaris were similar in all groups. The absolute and relative plantaris weights were greater in the Run-Load group compared with the Control and Run-No-Load groups. The mean fiber cross-sectional areas of FG, FOG, and SO fibers were 20, 25, and 15% greater in the Run-Load than in Control rats. In addition, these fiber types were 16, 21, and 12% larger in Run-Load than in Run-No-Load rats. The muscle weights and mean cross-sectional areas of each fiber type were highly correlated with the average running distances and total work performed in the Run-Load, but not the Run-No-Load, group. The slope of the relationship between fiber size and running distance and total work performed was significant for each fiber type but was higher for FG and FOG fibers compared with SO fibers. These data show that the load on a rat running voluntarily can determine the magnitude of a hypertrophic response and the population of motor units that are recruited to perform at a given loading condition.

The purpose of this study was to determine the effects of functional overload (FO) combined with growth hormone/insulin-like growth factor I (GH/IGF-I) administration on myonuclear number and domain size in rat soleus muscle fibers. Adult female rats underwent bilateral ablation of the plantaris and gastrocnemius muscles and, after 7 days of recovery, were injected three times daily for 14 days with GH/IGF-I (1 mg/kg each; FO + GH/IGF-I group) or saline vehicle (FO group). Intact rats receiving saline vehicle served as controls (Con group). Muscle wet weight was 32% greater in the FO than in the Con group: 162 +/- 8 vs. 123 +/- 16 mg. Muscle weight in the FO + GH/IGF-I group (196 +/- 14 mg) was 59 and 21% larger than in the Con and FO groups, respectively. Mean soleus fiber cross-sectional area of the FO + GH/IGF-I group (2,826 +/- 445 microm2) was increased compared with the Con (2,044 +/- 108 microm2) and FO (2,267 +/- 301 microm2) groups. The difference in fiber size between the FO and Con groups was not significant. Mean myonuclear number increased in FO (187 +/- 15 myonuclei/mm) and FO + GH/IGF-I (217 +/- 23 myonuclei/mm) rats compared with Con (155 +/- 12 myonuclei/mm) rats, although the difference between FO and FO + GH/IGF-I animals was not significant. The mean cytoplasmic volume per myonucleus (myonuclear domain) was similar across groups. These results demonstrate that the larger mean muscle weight and fiber cross-sectional area occurred when FO was combined with GH/IGF-I administration and that myonuclear number increased concomitantly with fiber volume. Thus there appears to be some mechanism(s) that maintains the myonuclear domain when a fiber hypertrophies.

The effects of growth hormone (GH) or insulin-like growth factor I (IGF-I) with or without exercise (ladder climbing) in countering the effects of unweighting on fast muscles of hypophysectomized rats during 10 days of hindlimb suspension were determined. Compared with untreated suspended rats, muscle weights were 16-29% larger in GH-treated and 5-15% larger in IGF-I-treated suspended rats. Exercise alone had no effect on muscle weights. Compared with ambulatory control, the medial gastrocnemius weight in suspended, exercised rats was larger after GH treatment and maintained with IGF-I treatment. The combination of GH or IGF-I plus exercise in suspended rats resulted in an increase in size of each predominant fiber type, i.e., types I, I + IIa and IIa + IIx, in the medial gastrocnemius compared with untreated suspended rats. Normal ambulation or exercise during suspension increased the proportion of fibers expressing embryonic myosin heavy chain in hypophysectomized rats. The phenotype of the medial gastrocnemius was minimally affected by GH, IGF-I, and/or exercise. These results show that there is an IGF-I, as well as a GH, and exercise interactive effect in maintaining medial gastrocnemius fiber size in suspended hypophysectomized rats.

The effects of 1 and 10 wk of functional overload (FO) of the rat plantaris with (FOTr) and without daily endurance treadmill training on its myosin heavy chain (MHC) composition were studied. After 1 and 10 wk of FO, plantaris mass was 22 and 56% greater in FO and 37 and 94% greater, respectively, in FOTr rats compared with age-matched controls. At 1 wk, pure type I and pure type IIa MHC fibers were hypertrophied in FO (39 and 44%) and FOTr (70 and 87%) rats. By 10 wk all fiber types comprising >5% of the fibers sampled showed a hypertrophic response in both FO groups. One week of FO increased the percentage of hybrid (containing both type I and type IIa MHC) fibers and of fibers containing embryonic MHC. By 10 wk, the percentage of pure type I MHC fibers was approximately 40% in both FO groups compared with 15% in controls, and the percentage of fibers containing embryonic MHC was similar to that in controls. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses showed an increase in type I MHC and a decrease in type IIb MHC in both FO groups at 10 wk, whereas little change was observed at 1 wk. These data are consistent with hypertrophy and transformation from faster to slower MHC isoforms in chronically overloaded muscles. The additional overload imposed by daily endurance treadmill training employed in this study (1.6 km/day; 10% incline) results in a larger hypertrophic response but appears to have a minimal effect on the MHC adaptations.

The effects of insulin-like growth factor (IGF-I) or growth hormone (GH) with and without exercise on predominantly slow muscles of hypophysectomized hindlimb-suspended (HS) rats were determined. HS resulted in a 21, 23, and 30% decrease in soleus, adductor longus, and vastus intermedius masses, respectively, compared with ambulatory rats. Compared with values in HS rats, IGF-I increased the vastus intermedius mass and GH or exercise alone increased both the soleus and vastus intermedius masses. There was a strong interactive effect between GH, but not IGF-I, and exercise in all three muscles of HS rats. The soleus fiber type distribution of HS rats was not affected by any treatment. HS resulted in a 24, 18 (P > 0.05), 32, and 20% (P > 0.05) decrease in the size of soleus fibers containing type I, IIa, I + IIa, and IIa + IIx myosin heavy chains, respectively, compared with ambulatory hypophysectomized rats. Hormone or exercise alone had no effect on fiber size in HS rats. However, all fiber sizes (except for type IIa + IIx in IGF-I with exercise rats) were larger in HS rats treated with GH or IGF-I and exercise than those in HS rats. These data indicate an interactive effect of both GH and IGF-I with exercise in maintaining fiber size of chronically non-weight-bearing predominantly slow muscles. Furthermore, the results suggest that the myosin heavy-chain phenotype in rats deficient in all pituitary factors is unresponsive to short-term administration of either GH or IGF-I or to exercise or HS.

Measures to attenuate muscle atrophy in rats in response to stimulated microgravity [hindlimb suspension (HS)] have been only partially successful. In the present study, hypophysectomized rats were in HS for 7 days, and the effects of recombinant human growth hormone (GH), exercise (Ex), or GH+Ex on the weights, protein concentrations, and fiber cross-sectional areas (CSAs) of hindlimb muscles were determined. The weights of four extensor muscles, i.e., the soleus (Sol), medial (MG) and lateral (LG) gastrocnemius, and plantaris (Plt), and one adductor, i.e., the adductor longus (AL), were decreased by 10-22% after HS. Fiber CSAs were decreased by 34% in the Sol and by 17% in the MG after HS. In contrast, two flexors, i.e., the tibialis anterior (TA) and extensor digitorum longus (EDL), did not atrophy. In HS rats, GH treatment alone maintained the weights of the fast extensors (MG, LG, Plt) and flexors (TA, EDL) at or above those of control rats. This effect was not observed in the slow extensor (Sol) or AL. Exercise had no significant effect on the weight of any muscle in HS rats. A combination of GH and Ex treatments yielded a significant increase in the weights of the fast extensors and in the CSA of both fast and slow fibers of the MG and significantly increased Sol weight and CSA of the slow fibers of the Sol. The AL was not responsive to either GH or Ex treatments. Protein concentrations of the Sol and MG were higher only in the Sol of Ex and GH + Ex rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Eccentric muscular actions involve the forced lengthening or stretching of muscles and tend to produce exertional injuries. This study used magnetic resonance (MR) imaging to serially evaluate muscles in five healthy, untrained subjects who performed exhaustive biceps exercise by doing isolated eccentric and concentric actions with a dumbbell. Symptoms were assessed, and T2-weighted images of the arms were obtained before exercise and 1, 3, 5, 10, 25, 40, 50, 60, and 80 days after exercise. Statistically significant increases in T2 relaxation times indicative of muscle injury occurred on each day of MR imaging evaluation in muscles performing eccentric actions, peaking on day 3 in two subjects; day 5, two subjects; and day 10, one subject. The pattern and extent of the abnormalities on MR images were variable. Pain, soreness, and joint stiffness were present on days 1, 3, and 5 in muscles that performed eccentric actions. MR imaging showed subclinical abnormalities that lasted as long as 75 days after the disappearance of symptoms (two subjects). Muscles that performed concentric actions had no changes in T2 relaxation times and were asymptomatic throughout the study.

Intramuscular electromyography (EMG) was used to determine and compare the recruitment patterns of the rat soleus (Sol), tibialis anterior (TA), and a deep and a superficial portion of the medial gastrocnemius (MG) during treadmill locomotion at various speeds and inclines and during swimming. Raw EMG signals for 10-20 step or stroke cycles were rectified, averaged, and processed to determine cycle period (EMG onset of one cycle to EMG onset of the next cycle), EMG burst duration, and integrated area of the rectified burst (IEMG). Mean EMG per burst was calculated as IEMG/burst duration. IEMG/min was calculated as IEMG times the number of bursts (cycles) per minute. Cycle period and burst duration of the extensors decreased hyperbolically, while the TA burst duration was unchanged, with increased treadmill speed. With increased treadmill speed, IEMG was decreased in the Sol and unchanged in the MG and TA, whereas IEMG/min decreased in the Sol and increased in the MG and TA. An elevation in treadmill incline resulted in an increase in the activation levels of the MG but not in the Sol or TA. These data indicate that the additional power required at increased speeds and/or inclines of treadmill locomotion is derived from the recruitment of the fast extensors, e.g., the MG. The mean cycle period during swimming was similar to that observed during the fastest treadmill locomotion. EMG burst durations and amplitudes, however, were higher in the TA, relatively similar in the MG, and lower in the Sol during swimming than treadmill locomotion.(ABSTRACT TRUNCATED AT 250 WORDS)

Eccentric (lengthening) muscle actions involve the forced lengthening of active muscles. Compared with concentric (shortening) muscle actions subjected to the same relative work load, eccentric actions have lower oxygen consumption requirements, fewer activated motor units, and less lactate production. This study was conducted to determine if T2-weighted MR could show any difference in muscles performing these specific types of actions and, therefore, be useful for physiologic investigations of eccentric and concentric actions. Five subjects performed exhaustive exercise by doing isolated concentric actions (raising a dumbbell, flexing at the elbow) and eccentric muscle actions (lowering a dumbbell, extending the contralateral arm). T2-weighted MR images of the arms were obtained immediately before and after exercise. Muscles that performed concentric actions had increases in signal intensity, whereas muscles that performed eccentric actions showed little or no change. T2 relaxation times increased significantly (p less than .01) in all volunteers, but T2 relaxation times for the muscles that performed concentric actions were significantly higher than those for muscles that performed eccentric actions (p less than .01). Therefore, T2 times increased with both concentric and eccentric actions, but the images failed to show the changes in the muscles that performed the eccentric actions. These data demonstrate that assessment of T2 values can be used to distinguish between muscles that perform concentric actions and those that perform eccentric actions, and this phenomenon may be useful for further physiologic investigations of these specific types of muscle actions.

Hindlimb locomotion on a motor-driven treadmill was studied in 5 cats spinalized at a low thoracic level adults. Six months after surgery, the cats were anesthetized and implanted for electromyographic (EMG) and force recordings in hindlimb muscles. For the last 5 months of the spinalization period, the hindlimbs of each cat were exercised daily for 30 minutes on a treadmill. Data were collected during hindlimb locomotion on a treadmill across the entire range of speeds each cat could accommodate. All trials were filmed (100 frames/s) for kinematic analysis. EMG data were recorded from the soleus (Sol), medial gastrocnemius (MG), tibialis anterior (TA) and extensor digitorum longus (EDL). Forces were recorded in vivo from the Sol and MG tendons. All cats could sustain full weight-bearing stepping without the need for mechanical stimulation of the tail. Although the general stepping pattern of the spinal cats was remarkably similar to that of normal cats, several key differences were identified. Compared to normal cats, the adult spinal cats walked at a lower range of speeds and exhibited a longer swing phase duration. The Sol produced forces and displayed activation periods comparable to those observed in normal cats. The MG of adult spinal cats, however, produced lower forces and had a later onset of activation in comparison to normal cats. Each of the muscles in all spinal cats exhibited tremor during stepping. These results suggest that there were limitations in the activation levels of some hindlimb flexor and extensor muscles during treadmill locomotion. These data further suggest that, in normal cats, accommodation to treadmill speed is accomplished by modulating supraspinal input to the lumbar spinal cord while leaving many of the timing details to be regulated by lumbar spinal networks.

Unloading the rat hindlimb results in a decrease in mass, especially in those muscles that normally have a load-bearing function. The present study was designed to evaluate the effect of intermittent periods of weight support in ameliorating this atrophic response. Adult male Sprague-Dawley rats were assigned to either a control (CON), a hindlimb suspended (HS), or a hindlimb suspended plus intermittent weight support (HS-WS) group. HS-WS rats were walked slowly on a treadmill at 0.2 m/s and a 19% incline for 10 min, every 6 h. After 7 d, the in situ mechanical properties of the soleus (Sol) and medial gastrocnemius (MG) were studied. Body weights of HS and HS-WS rats were 9 and 13% lower than CON. The SOl weight relative to body weight was 21 and 9% lower in HS and HS-WS than CON. Maximum tetanic tension relative to muscle mass was significantly lower in HS than CON, whereas HS-WS had values similar to CON. The MG weight relative to body weight was significantly lower in both suspended groups. The maximum tetanic tension relative to muscle weight was significantly elevated in HS-WS compared to CON, suggesting that weight support may have preferentially maintained the contractile protein component of the muscle. Contraction times were 25% faster (p less than 0.05) in the Sol and unchanged in teh MG of HS rats. For each muscle, the fatigue properties were similar in all groups. These data indicate that a low-force, short-duration exercise regime results in a significant functional recovery in the "slow" Sol, whereas the "fast" MG is less affected.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of iron deficiency anemia and iron treatment on blood gas and acid-base balance at rest and during exercise were studied. Eight Sri Lankan males and 13 females were randomly divided into an iron treatment or placebo group. Their initial hemoglobin (Hb) levels were 6.2 +/- 0.5 and 5.5 +/- 0.7 g/100 ml (mean +/- SEM) with serum iron levels of 41 +/- 8 and 30 +/- 6 micrograms/100 ml, respectively. Hemoglobin concentration was increased significantly within 7 days after iron treatment to 7.2 +/- 0.4 g/100 ml. Resting lactate was higher than normal, while base excess, buffer base, and actual bicarbonate were lower, maintaining a normal pH. Heart rates during exercise at a given work load and lactate production following exercise decreased after the elevation of Hb. Venous blood PCO2 rose as Hb concentration increased, preceding a significant increase in resting O2 content, 16 days after iron treatment. With anemia, O2 delivery is potentially maintained by a shift of the O2-dissociation curve to the right due, in part, to 2,3-diphosphoglycerate. There was no significant change in PO2 or Hb-O2% saturation following exercise or iron treatment. These data suggest that severe iron deficiency anemia results in lactate accumulation in blood even at rest but pH is maintained within normal limits. It was also suggested that severe anemia may impair CO2 transport capacity of blood which could limit continuation of muscle metabolism.

The purpose of the study was to describe changes that occur in the usage of fast-twitch and slow-twitch guinea pig hindlimb muscles, as estimated using chronically implanted electromyogram (EMG) electrodes, during voluntary locomotion under various conditions. Guinea pigs, in which fine wire electrodes were implanted in soleus (SOL) and lateral gastrocnemius (LG) muscles, were exercised at various speeds (13.4, 26.8, 40.2 m/min), grades (0-30%) and in some conditions loads (50-150 g) on a motor-driven treadmill. Bipolar EMG signals were rectified-averaged (RA-EMG) and analyzed for burst duration, amplitude, and the integral of each burst (IEMG). For each condition and muscle, total IEMG/min (IEMG/step x steps/min) was calculated and expressed as a percent of the maximum IEMG recorded. With increasing speed at 0% grade, the ratio of LG to SOL IEMG, each expressed as percent of maximum, remained constant at about 0.82. An increased stepping rate of 150 (at 13.4 m/min) to 225 (at 40.2 m/min) steps/min was accompanied by a 37% decrease in burst duration in LG and SOL. When the treadmill belt speed was increased from 13.4 to 4.02 m/min at 30% grade, the LG/SOL ratio increased from 0.83 to 1.03, whereas burst duration decreased by 49% (SOL) and 51% (LG). Soleus IEMG did not change significantly with increases in speed or grade; LG IEMG increased significantly with speed at 10% grade and with grade increase at the highest speed (40.2 m/min). These data provide some insight into how modifications of work load on a treadmill affect overall muscle activity and may assist in the interpretation of training-induced muscle biochemical alterations previously noted by other investigators.

Changes in haemoglobin (Hb), work performance, heart rate and postexercise blood lactate were studied in iron deficient, anaemic subjects for 16 d following total dosage infusion of iron dextran, i.v. (30-50 ml). Six adult men and 14 women were subjects with initial Hb levels of 6.6 +/- 0.6 g/dl (mean +/- SEM) for the iron treatment group (n=10) and 8.0 +/- 0.7 for the placebo group (saline infusion, n=10). Serum levels were 0.51 +/- 0.15 and 0.67 +/- 0.12 mg/l for the two groups, respectively. Haemoglobin and maximal work time increased significantly within 4 d after iron treatment and continued to increase up to 16 d. No changes were found in the placebo subjects. Heart rates at a given exercise intensity were lower in the iron treatment group than in control subjects who had the same Hb levels but had not been treated with iron. Post-exercise venous blood lactate was similar on succeeding days after iron treatment even though the subjects reached higher work loads. These results demonstrate the treatment of iron deficient, anaemic subjects with iron dextran results in improved work capacity within 4 d and a lower heart rate at a given work load after treatment which cannot be accounted for totally by the elevation of Hb concentration.

The effects of iron-deficiency anaemia on workers productivity were studied in a tea plantation in Sri Lanka. The quantity of tea picked per day was studied before and after iron supplementation or placebo treatment. After one month's treatment significantly more tea was picked when the haemoglobin (Hb) concentration was increased by iron supplementation than when it was not. The degree of improvement was greater in more-anaemic subjects (those with concentrations of 6.0-9.0 g Hb/dl). The level of physical activity of anaemic subjects in their everyday environment was also recorded for four or 24 hours continuously both before and after treatment. After three weeks these levels was significantly greater in the iron-treated than matched placebo-treated subjects. The economic implications of increased work productively with iron treatment are evident, particularly in developing countries. These results also provide strong evidence for the clinical impression that people with iron-deficiency anaemia suffer from tiredness and weakness.

The time course of metabolic and physiological adjustment to moderate iron deficiency anemia (MIDA, 8 g Hb/dl) and to severe iron deficiency anemia (SIDA, 4 g Hb/dl) was studied in adult, male Sprague-Dawley rats at 3, 7, 14, 30, 60, 90, 150, and 360 days, respectively. Our previous studies using the same rats used in the present study indicated that bone marrow iron was absent and plasma iron was significantly lower (p less than 0.001) in MIDA and SIDA relative to control. The following results with MIDA and SIDA rats are all expressed relative to control values. Red cell 2,3-diphosphoglycerate ranged from 45 to 146% greater in MIDA over the 360-day period and was 130% greater in SIDA at 30 days. Exhaustive run time consistently averaged 64 +/- 3% (SEM) less in MIDA over the time course and was further lowered to 18% in SIDA at 30 days. Heart rates of MIDA were elevated (p less than 0.05) at 180 days but lower (p less than 0.001) at 360 days in response to exercise. Resting heart rates of MIDA were the same at 180 and 360 days. Heart rates of SIDA were elevated (p less than 0.05) at rest and during exercise at 30 days. Organ weight/body weight changes indicated cardiomegaly in MIDA from 90 to 150 days which reverted to normal at 360 days; splenomegaly in MIDA from 90 to 360 days; and kidney atrophy in MIDA at 60 and 90 days which reverted to normal thereafter; in SIDA cardiomegaly and splenomegaly were present at 30 days. These results indicate that the onset and magnitude of physiological and metabolic adjustments occur in proportion to the severity of the anemia, and despite compensatory adjustments in parameters related to work performance, a new stable, lowered level of work tolerance is reached.

A qualitative histochemical assessment of glycogen loss in biopsies was made in bush-babies after running and jumping. Glycogen loss was related to the specific type of exercise. After running, glycogen loss was greatest in the slow-twitch oxidative fibre and depletion in the fast-twitch oxidative glycolytic fibres was similarly greater than in the fast-twitch glycolytic fibres. After jumping, the opposite pattern of glycogen utilization occurred (FG>FOG>SO).