Muscle morphology,enzyme activity and muscle strength in elderly men and women

Summary. The quadriceps muscle were investigated with respect to isometric and isokinetic muscle strength, morphology and as regards some enzymes and metabolites of importance for the contractile processes. The material comprises 52 men (66–76 years) and 13 women (61–71 years) without clinical symptoms. Some participants used antihypertensive and/or heart-regulating medicine but were symptom-free. None of the subjects participated in any systematic training. All of them except for one physically inactive woman carried out moderate physical activities for at least 4 hweek. The body cell mass was higher in the men than in the women, and was highly correlated to muscle strength in both sexes. The fibre distribution was similar in both sexes with an average of 48 % Type I fibres in the men and 54 % Type I fibres in the women. The women had fewer Type II B fibres (4%) than the men (18 %). The average Type I fibre area did not differ between the sexes. The average Type II fibre area and the mean fibre area were smaller in women than in men, so that the ratio between the mean Type II and Type I fibre area was smaller in the women (0–76) than in the men (0–95). Signs of denervation/reinnervation, such as type grouping and an increase number of enclosed fibres, were observed very rarely and no great number of atrophic fibres indicating neuropathy was found. In both sexes, there was a reduction in the Type II fibre size, specially in relation to Type I fibre size, compared with young people. There was no difference between the enzymatic (Mg²⁺ATPase, MK and LDH) and the phosphagen (ATP and CP) content values between the sexes and no correlation between these variables and muscle strength. The capillarization was similar in the men and the women.     

Capillary supply and muscle fibre types in patients with intermittent claudication: relationships between morphology and metabolism

Abstract There have been previous reports on an increased oxidative capacity in muscle tissue from the diseased legs of patients with intermittent claudication. The present study was designed to correlate metabolic and morphological data and to investigate whether the metabolic adaptive changes in muscle tissue of claudicating legs were also reflected in morphological variables such as capillary supply, fibre type distribution, and fibre area. The activity of cytochro-me-c-oxidase in gastrocnemius muscle was determined and the insulin and glucose uptakes were measured across the leg in the basal state and 10 min following intravenous administration of 25 g glucose. The finding of a reduced relative number of Type II B fibres and a reduced ratio Type II B/II A fibre area, as well as an increased capillary supply to Type II A, indicated that the most extensive morphologic changes in muscle tissue of claudicating legs had occurred in Type II fibres. The increased number of capillaries in contact with Type IIA fibres in muscle tissue from claudicating legs, compared with muscle tissue from control legs, suggested that the most apparent metabolic changes occurred in this fibre type in the adaptation process of these patients. The more pronounced morphologic and metabolic changes in Type II fibres suggest that these fibres are more intensely activated than Type I fibres during physical activity in claudicating legs. The insulin uptake correlated positively with the number of capillaries per fibre, suggesting that the endothelial surface area is one of the determining factors for insulin uptake. The percentage of Type II B fibres reflected to a certain extent the metabolic adaptation in muscle tissue.     

Capillary supply and muscle fibre types in patients with intermittent claudication: relationships between morphology and metabolism

Abstract. There have been previous reports on an increased oxidative capacity in muscle tissue from the diseased legs of patients with intermittent claudication. The present study was designed to correlate metabolic and morphological data and to investigate whether the metabolic adaptive changes in muscle tissue of claudicating legs were also reflected in morphological variables such as capillary supply, fibre type distribution, and fibre area. The activity of cytochro-me-c-oxidase in gastrocnemius muscle was determined and the insulin and glucose uptakes were measured across the leg in the basal state and 10 min following intravenous administration of 25 g glucose. The finding of a reduced relative number of Type II B fibres and a reduced ratio Type II B/II A fibre area, as well as an increased capillary supply to Type II A, indicated that the most extensive morphologic changes in muscle tissue of claudicating legs had occurred in Type II fibres. The increased number of capillaries in contact with Type IIA fibres in muscle tissue from claudicating legs, compared with muscle tissue from control legs, suggested that the most apparent metabolic changes occurred in this fibre type in the adaptation process of these patients. The more pronounced morphologic and metabolic changes in Type II fibres suggest that these fibres are more intensely activated than Type I fibres during physical activity in claudicating legs. The insulin uptake correlated positively with the number of capillaries per fibre, suggesting that the endothelial surface area is one of the determining factors for insulin uptake. The percentage of Type II B fibres reflected to a certain extent the metabolic adaptation in muscle tissue.     

The influence of functional electrical stimulation on the properties of vastus lateralis fibres following total knee arthroplasty.

The influence of functional electrical muscle stimulation (FES) on selected properties of vastus lateralis muscle fibres was studied in patients recovering from total knee arthroplasty for osteoarthritis. Prior to surgery, on the average, muscle biopsies from the vastus lateralis could be characterized as having a predominance of Type I fibres which were significantly larger in cross-sectional area than the Type II fibres in the same sample. Following surgery, muscle biopsies from a group of patients (n = 7) which received continuous passive motion and no FES, exhibited a marked increase in the proportion of Type II fibres along with a general atrophy of both the Type I and Type II fibres. Patients receiving passive motion and FES (n = 9) also showed an increase in the relative percentage of Type II fibres. Post-operatively, however, there was no significant reduction in fibre area in the stimulated muscles. These data suggest that FES was effective in attenuating the muscle atrophy associated with total knee arthroplasty but had no influence on those metabolic properties which were related to muscle fibre type classification criteria.     

Effects of strength and endurance training on muscle fibrecharacteristics in elderly women

The effects of 18weeks’ intensive strength and endurance training on fibre characteristics of the vastuslateralis muscle were studied in 76- to 78-year-old women. Type I and type IIa fibresconstituted over 90% of the cell population and were almost equally represented. Nochanges were observed in the proportions of the different fibre types. When comparing thebaseline and the 18-week measurements within the groups, the strength group showed a meanincrease of 34% (P=0·028) in mean type I fibre area. Thefrequency histograms showed an increased proportion of larger type I fibres after strengthtraining and a decreased proportion of smaller type IIa fibres after endurance training. In thecontrol subjects, the proportion of smaller type I and type IIa fibres increased during theexperimental period. The results indicate that intensive strength training induces type I fibrehypertrophy, whereas the effects of endurance training are less evident. The considerablevariation found in the change in muscle fibre cross-sectional areas is also noteworthy.     

Muscle adaptations and glucose control after physical training in insulin-dependent diabetes mellitus

Summary. Six men and three women with insulin-dependent diabetes (without complications) participated in physical training three times a week for 20 weeks. Physical training did not change the concentration of fasting blood-glucose, glucose excretion in urine or glucosylated haemoglobin (Hb_A1). However, the glucose disposal rate during euglycaemic clamp increased after training. In two patients a minor reduction of insulin dosage was necessary to alleviate slight hypoglycaemic episodes. The training resulted in significant increases in quadriceps isometric and dynamic strength and endurance. Maximal oxygen uptake increased by 8%, the activity of glycolytic enzymes in vastus lateralis muscle by 47% for hexokinase, and 30% for tri-osephosphate dehydrogenase and 25% for lactic dehydrogenase, the activity of oxidative enzymes by 42% for citrate synthase and 46% for 3-hydroxy-acyl-CoA-dehydrogenase. The glycogen concentration in the vastus lateralis muscle did not change significantly. Lipoprotein lipase activity did not change in muscle, nor in adipose tissue. The mean muscle fibre area increased by 25% and the area of FTa fibres by 30%. The new formation of capillaries around different muscle fibres was significant for FTb fibres (26%). The proliferation of capillaries, however, appeared to be insufficient to cope with the increased area of muscle fibres. As a result, the mean area of muscle fibre supplied by one capillary (a measure of diffusion distance) significantly increased after training for FTa fibres. It is concluded that with the exception of deficient proliferation of capillaries, patients with insulin-dependent diabetes mellitus show a normal central and peripheral adaptation to physical training. Physical training does not apparently improve blood glucose control in most cases, despite an increased insulin sensitivity.     

Serum carnosinase activities in patients with alcoholic chronic skeletal muscle myopathy

1. Serum carnosinase activity was assayed in a group of alcoholic patients with and without histologically proven atrophy of type II skeletal muscle fibres, and in control subjects. No significant activity was detected in muscle biopsy samples or washed erythrocytes. 2. Serum carnosinase activity was significantly lower in chronic alcoholic patients compared with a group of age-matched controls. Alcoholics with abnormal muscle biopsies had significantly lower enzyme activities than either those patients with normal muscle biopsies or the controls. Serum enzyme activities in patients with normal muscle biopsies were not significantly different from controls. 3. Serum carnosinase activity was inversely correlated with the degree of muscle atrophy as measured by the type II fibre atrophy factor. There was a positive correlation between the enzyme activity and skeletal muscle mass as reflected by the creatinine-height index. Furthermore, the enzyme activity significantly increased, with resolution or improvement in the myopathy, in patients who abstained from alcohol. 4. Kinetic studies showed that the reduced carnosinase activity was due mainly to a decrease in the apparent Vmax. The apparent Km was significantly higher in the myopathic compared with non-myopathic alcoholics. Mixing serum from controls and patients with myopathy gave the expected values, indicating the absence of a serum enzyme inhibitory factor. Acute alcohol loading had no effect on the serum carnosinase activity. 5. The decrease in serum carnosinase activity in alcoholics was not related to the severity of their liver disease. Assays of serum carnosinase in chronic alcoholics, can thus be used as a marker of their associated myopathy.     

Dynamic muscle strength alterations to detraining and retraining in elderly men

To investigate the effects of cessation and subsequent resumption of training on muscle strength in elderly men, 11 men (aged 65–77 years), just completing a 24-week randomized controlled trial of recombinant human growth hormone (rhGH) and resistance exercise (rhGH, n=6; placebo, n=5), detrained for 12 weeks and subsequently retrained for 8 weeks. During the detraining and retraining phase, subjects did not receive rhGH. The resistance programme included three sets of eight repetitions at 75% of one-repetition maximum (1-RM), three times per week, for 10 upper and lower body exercises. Dynamic muscle strength was assessed by the 1-RM method every 2 weeks for 44 weeks. Needle biopsies of vastus lateralis muscle were obtained from seven men. Muscle strength increased during initial training by 40·4±5·5% (mean±SEM), ranging from 26·0±5·0 to 83·9±15·6%, depending on muscle group. Increased strength was accompanied by hypertrophy (P<0·05) of type I (17·4±4·1%) and II (25·8±12·4%) muscle fibres. Of initial strength gains, only 29·9±5·2% was lost with detraining. However, type I and II fibre cross-sectional area reverted to pretraining values. After 8 weeks of retraining, muscle strength returned to trained values, but without a significant change in fibre morphology. The results indicate that elderly men lose some muscle strength following short-term detraining, but that only a brief period of retraining suffices to regain maximal strength. Reversal of fibre cross-sectional area with detraining, and only modest improvement with retraining, suggests that much of the retention in strength with detraining and reacquisition of lost strength with retraining reflects neural adaptation.     

High blood pressure and muscle morphology/metabolism – causal relationship or only associated factors?

As muscle tissue constitutes a main target organ for glucose metabolism and is responsible for the development of insulin resistance, it seems plausible to elucidate the relationship between blood pressure and muscle morphology and metabolism. The association between blood pressure and capillarization/morphology of the vastus lateralis muscle and metabolic variables was evaluated in 24 perimenopausal obese women [body mass index (BMI) 34·9 ± 1·1; waist–hip ratio (WHR) 0·90 ± 0·02]. The muscle enzyme activity of lipoprotein lipase (LPL), citrate synthase and glycogen synthase was determined. There was a significant negative correlation between the percentage of type I fibres and relative fibre area of type I on the one hand and systolic and diastolic blood pressure on the other. There was a negative correlation between the capillary density (i.e. number of capillaries/muscle fibre) and a positive correlation between the diffusion distance (fibre area supplied by one capillary) and diastolic blood pressure. The activities of LPL and citrate synthase were positively correlated with the percentage of type I and negatively correlated with the percentage of type II muscle fibres. The activity of LPL was also negatively correlated with plasma glucose and the insulin/C-peptide ratio. The insulin/C-peptide ratio was positively correlated with the percentage of type II muscle fibres. In stepwise multiple regression analyses, 20–30% of the variation in systolic and diastolic blood pressure could be explained by the variables of muscle fibre distribution. Excluding muscle morphological variables from the regression model, the insulin/C-peptide ratio accounted for 13% of the variation in systolic and diastolic blood pressure. The results of the study show the close association between muscle morphology and blood pressure. It remains to be elucidated whether this association indicates a causal relationship.     

Microphotometry of single fibres from the quadriceps muscle in man

Two main types of muscle fibres were histochemically identified in the lateral portion of the human quadriceps muscle. Muscle samples were obtained by needle biopsies from a highly trained, a hypotrophied and a normal leg. Serial sections were histochemically stained for myofibrillar ATPase (pH 9.4, preincubation at pH 10.3), nicotinamide adenine dinucleotide tetrazolium oxidoreductase (NADHTR) and α-glycerophosphate dehydrogenase (α-GPD, E.C.1.1.2.1.). In the two fibre types identified in the ATPase stained sections, type I (ATPase negative) and type II (ATPase positive), microphotometry was used to quantify the oxidative (NADHTR) and glycolytic (α-GPD) enzyme activity of the single fibre. The correspondence to the ATPase ‘type’ was 100% when the activity of both metabolic enzymes were combined as a ‘metabolic profile’ for each fibre. This clear distinction was unaffected by the training state of the muscle. It is concluded that histochemical reaction for myofibrillar ATPase as well as the combination of quantified NADHTR and α-GPD activity reveals the same distinct separation of human muscle fibres in two main types. The microphoto-metric technique seems useful on histochemically treated muscle sections when quantitation in each fibre type is essential as, e.g. in relation to specific illness or training.     

Effects of resistance training on cardiovascular responses to lower body negative pressure in the elderly

The purpose of the present study was to determine whether resistance training alters the cardiovascular responses to submaximal lower body negative pressure (LBNP) in the elderly. Twenty‐one subjects were randomized into a control (C: n=10; 70 ± 3 years, mean ± SD) or a resistance training (TR: n=11; 67 ± 7 years) group. Subjects in the TR underwent 12 weeks of training consisting of three sets of 8–12 contractions at ?60–80% of their initial maximal one repetition, three times per week, on 10 different machines. Before (Pre) and after (Post) training, all subjects underwent exposures of LBNP of ?10, ?20 and ?40 Torr and muscle biopsy sampling at the vastus lateralis. TR increased (P≤0·05) knee extension (Pre=379 ± 140 N, Post=534 ± 182 N) and chest press (Pre=349 ± 137 N, Post=480 ± 192 N) strength. Neither body weight nor percentage body fat were altered (P >0·05) by training. Resistance training increased (P≤0·05) cross‐sectional area in both Type I (4203 ± 1196 to 5248 ± 1728 μm²) and Type II (3375 ± 1027 to 4286 ± 1892 μm²) muscle fibres. Forearm blood flow, forearm vascular conductance, mean arterial pressure, and heart‐rate responses to LBNP were not altered by the training. These data suggest that the cardiovascular responses of elderly to LBNP are unaffected by 12 weeks of whole‐body resistance training despite increases in muscle strength and size.     

The effect of aerobic and resistance exercise training on the health related quality of life,physical function,and muscle strength among hemodialysis patients with Type 2 diabetes

IntroductionDiabetic patients who undergo hemodialysis commonly suffer from reduction of both exercise capacity and muscle strength. These factors may have a negative effect on health related quality of life (HRQoL) and physical function. We investigated the effect of aerobic and resistance exercise training on the HRQoL, physical function, and muscle strength among hemodialysis patients with Type 2 diabetes.MethodsTwenty-eight diabetic patients who were on hemodialysis in the Milad Hospital (Tehran, Iran) were recruited for the study. Subjects were randomized into control (n = 13) and exercise training groups (n = 15). The exercise training group performed combined aerobic and resistance exercise training at moderate intensity (11–15/20 on the Borg scale) during hemodialysis treatment, 3 times a week for 8 weeks. The primary outcomes consisted of physical function measured by a 6-min walk test (6MWT), HR-QoL measured by the Short Form Health Survey (SF-36), and lower limb muscle strength measured using a hand-held Digital Dynamometer.ResultsThe 6MWT distance increased significantly in the exercise training group (36%). Bilateral hip flexor strength (right, 24.5%; left, 30.4%) and abductor strength (right, 27.6%; left, 25.2%) decreased significantly in the non-exercising control group but no significant change was found in the exercise group (P > 0.05). There were no significant changes in any of the 8 generic subscales of HR-QoL neither in the exercise training group nor controls following an 8- week study.Conclusions8 weeks of combined aerobic-resistance exercise training among diabetic hemodialysis patients seem to be effective in improvement of physical function and lower limb muscle strength.     

The influence of prednisone on the muscle morphology and muscle enzymes in patients with rheumatoid arthritis

Thirty-five female patients, mean age 63 years, suffering from rheumatoid arthritis participated the study. Twenty patients had been on long-term low-dose corticosteroid treatment. Fifteen patients had never received corticosteroids. A control group of 15 age- and sex-matched healthy subjects was also studied. Examination of muscle biopsies from the (right) vastus lateralis and measurements of isokinetic and isometric knee-extension muscle strength were performed in all subjects. Rheumatoid arthritis patients treated with corticosteroid showed a low percentage of type I fibres, mean 35.7 (range 17-66) % compared with patients who did not receive corticosteroid (P less than 0.005). The latter group did not differ from the controls. The muscle fibre areas also were affected in the corticosteroid treated rheumatoid patients. Type I and type II mean fibre areas were reduced by 32% and 50%, respectively, when compared with non-prednisone treated patients. The latter group did not differ from the controls in this respect. A correlation was found between the isokinetic muscle strength of the knee extensors and the mean areas of type I and type II in patients treated with prednisone (r = 0.48, P less than 0.05 and r = 0.58, P less than 0.02 respectively). No such correlation was found when using isometric measurements of the knee extensors. A positive correlation was found in both groups of rheumatoid arthritis patients between the areas of the type I and type II fibres (r = 0.66 - 0.68, P less than 0.05 - 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Human skeletal muscle metabolism and morphology after temporary incomplete ischaemia

Abstract. Incomplete ischaemia was caused by clamping the aorta during reconstructive vascular surgery. After restoration of the blood flow extensive metabolic and morphological changes in the muscle tissue were observed. The adenylate (ATP + ADP + AMP) and the creatine (PCr + Cr) pools declined 30–40% and the energy charge of the adenine nucleotides dropped significantly. The metabolic pool changes were closely related to the changes in the lactate/pyruvate ratios. Morphological signs of membrane disturbances, such as fibre oedema and swelling of mitochondria, were seen in many muscle fibres 30 min after declamping. 5 days postoperatively, a number of mitochondrial abnormalities were observed and fibre regeneration was seen in places. The relative number of Type 2 fibres and the width of the capillary lumen were both related to the decrease of the metabolic parameters. Thus, the metabolic state and the fine structure of the incompletely ischaemic muscle were closely related to each other. The amount of Type 2 fibres seemed to be of special importance for the patho-physiological events in intermittently ischaemic muscle fibres.     

Effect of hyperthyroidism on fibre-type composition,fibre area,glycogen content and enzyme activity in human skeletal muscle

Summary. Seven hyperthyroid patients were studied by repeated muscle biopsies (vastus lateralis) before and after a period of medical treatment which averaged 10 months. The biopsies were analysed with regard to fibre-type composition, fibre area, capillary density, glycogen content and enzyme activities representing the glycolytic capacity (hexokinase, 6-phosphofructokinase), oxidative capacity (oxoglutarate dehydrogenase, citrate synthase) and Ca²⁺- and Mg²⁺-stimulated ATPase in muscle. In the pretreatment biopsy (hyperthyroid state), there was a significantly lower proportion of type I fibres (30% vs. 41%), a higher capillary density (23%), lower glycogen content (33%), and higher hexokinase activity (32%) compared with the post-treatment biopsy. No significant changes in the activity of the remaining enzymes were observed. The present study indicates that hyperthyroidism induces a transformation from type I to type II fibres in human skeletal muscle. The increase in hexokinase activity probably reflects a higher glucose utilization by skeletal muscle in order to compensate partially for the reduced glycogen content.     

Muscle fibre types, ubiquinone content and exercise capacity in hypertension and effort angina

The composition of skeletal muscle fibre expressed as a percentage of slow twitch (ST), type I or "red" and fast twitch (FT), type II or "white" were determined in patients with hypertension (HT) or with severe ischaemic heart disease (IHD) and compared to age matched controls. Similarly, exercise capacity expressed as the cycle intensity eliciting a blood lactate concentration corresponding to 2.0 mmol x 1-1 were compared with healthy controls. Both patient groups had a higher percentage of FT fibres with relatively lower exercise capacities than their controls. The exercise capacities were reduced even when the relationship of decreased capacity with the percentage of increased FT was considered. There was an increase IHD but not in HT in patients with fibre subgroup FTc, which most probably reflected fibre trauma. Both patient groups were low in the skeletal muscle mitochondrial electron carrier and unspecific antioxidant ubiquinone, coenzyme Q10 or CoQ10. Patients with IHD but not HT showed, however, a faster fall in the ratio CoQ10 over ST% the higher the percentage value of ST. The ratio reflects the antioxidant activity related to CoQ10 in the fibre hosting most of the oxidative metabolism. A low ratio indicates a risk of metabolic lesion and cell trauma. This could explain fibre plasticity and offer an alternative cause to heredity in elucidating in deviating muscle fibre composition in patients with HT and IHD.     

Skeletal muscle fibre types and sizes in anorexia nervosa patients

Summary. Fibre type composition and fibre areas in skeletal muscle of anorexia patients were studied on biopsies from the m. quadriceps femoris in five male and five females, whose body weight was 2–3-5 SDs less than expected from the normal weight/height relationship. In two of the males, the muscle studies were also made after rehabilitation. A higher than normal percentage of type I fibres was found in the patients (male, 62 ±12, female, 69 ±7) whereas the percentage of type IIA fibres did not differ from normal individuals (male, 38 ±12, female 24 ±15). Of note was the observation that no type IIB fibres were found and some patients had an increased occurrence of the normally rare type IIC fibres. All muscle fibres were markedly atrophied with the mean cross-sectional area of type IIA fibres being significantly smaller (male, 26-1 ±3–7, female, 21-2 ±10-3, fi.m²×10^-2) than the mean area of type I fibres (male, 34-1 ±4–7, female, 35-3±7-4, (j.m²× 10^-2). In the two males studied after rehabilitation (body weight increased 12 and 19 kg), mean fibre area had increased by 40%. Our results suggested that a predominant part of the reduction in body weight and lean body mass, seen in adolescent children suffering from anorexia nervosa, could be accounted for by a loss of skeletal muscle mass. In the six subjects where marker enzymes of glycolytic (TPDH, LDH) and mitochondrial pathways (CS, HAD) were assayed, the former were 50% and the latter 10–20% below sedentary controls. Maximal oxygen uptake was only 35 (males) and 29 (females) ml/kg min^-1; this contrasted with the physical activity pattern of these patients, yet was in line with their small muscle mass with its low oxidative potential.     

Isokinetic strength training in below-knee amputees

Eight below-knee amputees performed isokinetic training of knee extensor- and knee-flexor muscles for a period of 8-12 weeks at angular velocities of 60 degrees/s, 180 degrees/s and 240 degrees/s. Before and after training isokinetic and isometric knee extensor/flexor strength was measured. Muscle biopsies were taken from the vastus lateralis and the cross-sectional area of the thigh muscles was measured with computerized tomography. Peak torque of the amputated leg increased significantly in all knee-extension tests and in knee-flexion at 180 degrees/s, and in the non-amputated leg in extension at 180 degrees/s, 240 degrees/s and for isometric strength at 60 degrees knee angle. Knee-flexion strength increased at 240 degrees/s. The cross-sectional area of the muscle fibers increased in the amputated leg in all patients except one. There was no significant increase in the non-amputated leg which also was trained. The quotient between the cross-sectional areas of type II and type I fibers increased from 1.04 to 1.20 in the amputated leg, demonstrating an increase specially in the type II fibers. There was no difference in the non-amputated leg. The cross-sectional area of the thigh muscles did not show any significant change in either leg. The patients estimated their ability to walk after training to more than double the distance compared to before training. They could also manage better without walking aids. The increase in strength and the synchronous increase in the size of type II (fast twitch) fibers indicate that the training model has activated also these motor units which probably have not been given as much training earlier.     

Muscle relaxation rate, fibre-type composition and energy turnover in hyper- and hypo-thyroid patients

1. Quadriceps strength, relaxation rate, fibre-type composition and energy-turnover rate during a submaximal contraction have been measured in hypo- and hyper-thyroid patients and compared with findings in normal subjects. 2. Six out of eight hypothyroid patients had normal strength whereas four out of five hyperthyroid patients were weak. 3. Relaxation rate was decreased in all the hypothyroid patients but increased in only three out of five hyperthyroid patients. 4. In hypothyroidism there was a marked reduction in the percentage contributed by type II fibres to muscle cross-section, partly due to type II atrophy but also due to a decrease in the relative frequency of type II fibres. In hyperthyroidism both fibre types tended to atrophy. 5. The rate of ATP turnover during submaximal contraction held to fatigue was reduced in hypothyroidism. This was probably due to decreased ATP utilization rather than an impaired supply of energy-supplying substrates. In hyperthyroidism the rate of ATP turnover was increased. 6. Altered relaxation rate and ATP-turnover rate may be explained on the basis of changes in myosin ATPase activity with thyroid status. Changes in muscle-fibre-type composition, as determined histochemically, could not per se account for the functional abnormalities.     

Alcoholic skeletal myopathy, a clinical and pathological study

One hundred and fifty-one inpatients with a history of chronic heavy alcohol intake were examined for evidence of muscle disease. Ninety-two patients (60 per cent) had histologically abnormal biopsies of the quadriceps muscle. The most common abnormality, which was often severe, was type II muscle fibre atrophy. Seven patients (5 per cent) had histological evidence of acute myopathy, one of whom presented with the full clinical picture of acute rhabdomyolysis. Twenty-three patients had cirrhosis, 36 were significantly malnourished and 98 had evidence of a peripheral neuropathy. None of these features, however, were sufficient to account for the muscle abnormalities. There was no clear relationship between musculo-skeletal symptoms and muscle biopsy histology. Serum creatine kinase activity was elevated in only 23 subjects and was an insensitive indicator of subclinical acute myopathy and of chronic alcoholic myopathy. Follow-up studies after abstinence from alcohol invariably showed both objective and subjective improvement of muscle function - often in the absence of any clinical recovery from the peripheral neuropathy. Continued alcohol consumption was accompanied by persistence and often deterioration of muscle fibre atrophy. It is concluded that chronic skeletal myopathy is a frequent consequence of alcohol abuse and may result from a direct toxic effect of ethanol on muscle fibres.