Thigh Muscle Mass Research Articles

Comparison of DXA and CT in the Assessment of Body Composition in Premenopausal Women With Obesity and Anorexia Nervosa

Accurate methods for assessing body composition in subjects with obesity and anorexia nervosa (AN) are important for determination of metabolic and cardiovascular risk factors and to monitor therapeutic interventions. The purpose of our study was to assess the accuracy of dual-energy X-ray absorptiometry (DXA) for measuring abdominal and thigh fat, and thigh muscle mass in premenopausal women with obesity, AN, and normal weight compared to computed tomography (CT). In addition, we wanted to assess the impact of hydration on DXA-derived measures of body composition by using bioelectrical impedance analysis (BIA). We studied a total of 91 premenopausal women (34 obese, 39 with AN, and 18 lean controls). Our results demonstrate strong correlations between DXA- and CT-derived body composition measurements in AN, obese, and lean controls (r = 0.77-0.95, P < 0.0001). After controlling for total body water (TBW), the correlation coefficients were comparable. DXA trunk fat correlated with CT visceral fat (r = 0.51-0.70, P < 0.0001). DXA underestimated trunk and thigh fat and overestimated thigh muscle mass and this error increased with increasing weight. Our study showed that DXA is a useful method for assessing body composition in premenopausal women within the phenotypic spectrum ranging from obesity to AN. However, it is important to recognize that DXA may not accurately assess body composition in markedly obese women. The level of hydration does not significantly affect most DXA body composition measurements, with the exceptions of thigh fat.

Predictors of maximal short-term power outputs in basketball players 14–16 years

Relationships between growth, maturation and maximal short-term power outputs were investigated in 94 youth basketball players aged 14-16years. Data included chronological age (CA), skeletal age (SA), years of training; body dimensions, estimated thigh volume, a running based short-term exercise assessed by the line drill test (LDT), the Bangsbo sprint test (BST) and short-term muscle power outputs with the Wingate anaerobic test (WAnT). Multiple linear regression analyses were used to estimate the effects of CA, skeletal maturity (SA/CA), years of training experience, body size and lower-limb volume on short-term performance in the LDT, BST and WAnT, respectively. Explained variances differed between cycle-ergometry outputs (52-54%) and running test performances (23-46%). The independent effects of predictors were small in the fatigue scores of the WAnT (4%) and the BST (11%). Skeletal maturity, body mass and leg length were primary predictors for all maximal short-term power output measures. Leg length was more relevant as a predictor than stature in the WAnT outputs, while stature and body mass appeared in the model with the running tests as dependent variable. Maximal short-term running abilities were also sensitive to years of training. In summary, skeletal maturation, body size and thigh muscle mass explained moderate to large proportions of the variance on maximal short-term performances of adolescent basketball players. The results highlight the importance of considering maturity status in evaluating the maximal short-term power outputs of adolescent athletes.

Association of abdominal visceral adiposity and thigh sarcopenia with changes of arteriosclerosis in haemodialysis patients

In haemodialysis (HD) patients, abdominal visceral fat is accumulated while lean body mass is decreased irrespective of their body mass indexes (BMI). However, it is poorly understood which changes of fat and muscle masses are more associated with changes of arteriosclerosis. We aimed at examining the associations of abdominal visceral fat and thigh muscle masses with markers of arteriosclerosis in chronic HD patients in a cross-sectional fashion. We measured abdominal visceral fat mass area (AVFA), abdominal subcutaneous fat mass area (ASFA), thigh muscle area (TMA) and TMA standardized for femoral shaft area (TMA/FSA) by computed tomography (CT) in 161 HD patients (age: 61 ± 11 years, time on HD: 12 ± 10 years, male/female = 113/48, non-diabetes/diabetes = 127/34). We also investigated carotid artery intima-media thickness (CA-IMT) using the ultrasound instrument, and brachial-ankle pulse wave velocity (baPWV), cardio-ankle vascular index (CAVI) and ankle-brachial pressure index (ABI) using the waveform device (CAVI-VaSera VS-1000). AVFA was significantly and positively related to CA-IMT in both non-diabetic (r = 0.23, P < 0.05) and diabetic HD patients (r = 0.38, P < 0.05). There was a significant and positive correlation between AVFA and hs-CRP in all patients (r = 0.26, P < 0.01). ASFA was also significantly correlated with CA-IMT (r = 0.53, P < 0.01) in diabetic HD patients. TMA/SFA ratio was negatively associated with CA-IMT (r = - 0.21, P < 0.05), while positively with ABI (r = 0.28, P < 0.01) in non-diabetic patients. TMA/SFA ratio was inversely related to baPWV (r = - 0.41, P < 0.01) and CAVI (r = - 0.41, P < 0.05) in diabetic HD patients. Multiple regression analysis revealed that AVFA was a significant determinant of CA-IMT. TMA/AFA was also significantly associated with CA-IMT, baPWV, CAVI and ABI. Accumulated abdominal visceral fat is associated with CA-IMT. In addition, reduced thigh muscle mass area is independently related to CA-IMT, baPWV, CAVI and ABI, suggesting that sarcopenia in the leg is closely associated with systemic changes of arteriosclerosis in HD patients.

Performances in extreme environments: effects of hyper/hypobarism and hypogravity on skeletal muscle

Many environmental factors may affect muscle plasticity but some have exclusive characteristics that allow them to play a key role to maintain the muscle capacity to generate force; these factors are: i) the oxygen availability and ii) the load applied to muscle fibres. Hyperbarism is a condition that occurs when a man is subjected to pressure increases. To keep the lungs from collapsing, the air is supplied to him under high pressure which exposes the blood in the lungs to high alveolar gas pressures. Under this condition, the PO2 become sufficiently increased, serious disorders may occur, such as modification of oxygen delivery and/or oxygen availability to permit regular muscle contraction. Also altitude hypobaric hypoxia induces modification of muscle capacity to generate work. Prolonged exposure to high altitude leads significant loss in body mass, thigh muscle mass, muscle fiber area and volume density of muscle mitochondria. Spaceflight results in a number of adaptations to skeletal muscle, including atrophy and early muscle fatigue. Muscle atrophy is observed in a wide range of muscles, with the most extensive loss occurring in the legs, because astronauts are no longer needed to support the body's weight. This review will describe the background on these topics suggesting the strategies to correct the specific muscle changes in presence of environmental stresses, such as the alteration in oxygen-derived signaling pathways or the metabolic consequence of microgravity that may indicate rational interventions to maintain muscle mass and function.

Performances in extreme environments: effects of hyper/hypobarism and hypogravity on skeletal muscle

Many environmental factors may affect muscle plasticity but some have exclusive characteristics that allow them to play a key role to maintain the muscle capacity to generate force; these factors are: i) the oxygen availability and ii) the load applied to muscle fibres. Hyperbarism is a condition that occurs when a man is subjected to pressure increases. To keep the lungs from collapsing, the air is supplied to him under high pressure which exposes the blood in the lungs to high alveolar gas pressures. Under this condition, the PO2 become sufficiently increased, serious disorders may occur, such as modification of oxygen delivery and/or oxygen availability to permit regular muscle contraction. Also altitude hypobaric hypoxia induces modification of muscle capacity to generate work. Prolonged exposure to high altitude leads significant loss in body mass, thigh muscle mass, muscle fiber area and volume density of muscle mitochondria. Spaceflight results in a number of adaptations to skeletal muscle, including atrophy and early muscle fatigue. Muscle atrophy is observed in a wide range of muscles, with the most extensive loss occurring in the legs, because astronauts are no longer needed to support the body's weight. This review will describe the background on these topics suggesting the strategies to correct the specific muscle changes in presence of environmental stresses, such as the alteration in oxygen-derived signaling pathways or the metabolic consequence of microgravity that may indicate rational interventions to maintain muscle mass and function.

One Year of Growth Hormone Treatment in Adults with Prader-Willi Syndrome Improves Body Composition: Results from a Randomized, Placebo-Controlled Study

Prader-Willi syndrome (PWS) is a multisymptomatic disease that shares many similarities with the GH deficiency syndrome, including altered body composition with more body fat than lean body mass. Our objective was to investigate the effect of GH on body composition in adults with PWS. Forty-six adults with PWS were randomized to GH or placebo treatment for 12 months in a double-blind trial. We evaluated change in regional body composition of the abdomen and thigh as measured by computed tomography and change in total body composition as measured by dual-energy x-ray absorptiometry. Forty patients completed the study. Baseline median IGF-I sd score was -0.4. GH treatment increased IGF-I by 125 μg/liter (1.51 sd score), and based upon computed tomography, body composition improved with a decrease in visceral fat mass of 22.9 ml (P = 0.004), abdominal sc fat mass 70.9 ml (P = 0.003), and thigh fat mass 21.3 ml (P = 0.013), whereas thigh muscle mass increased 6.0 ml (P = 0.005). By dual-energy x-ray absorptiometry, lean body mass improved 2.25 kg (P = 0.005), and total fat mass decreased 4.20 kg (P < 0.001). No major side effects were seen. Unrelated to the GH-IGF-I levels at baseline, our results showed that long-term treatment with GH effectively improved body composition and represents a safe, potential treatment option, relieving some of the negative consequences of PWS.

Arterial stiffness is associated with low thigh muscle mass in middle-aged to elderly men

ObjectiveSarcopenia of legs is an important cause of physical dysfunctions, frailty and dependence. Many predisposing and underlying mechanisms of sarcopenia, including age, sedentary life style, oxidative stress, insulin resistance, and low testosterone levels, are also known to be related to atherosclerosis, which is another leading cause of morbidity and mortality in elderly subjects. In this study, we investigated our hypothesis that sarcopenia and atherosclerosis are associated with each other to facilitate mutual abnormalities. MethodsStudy was performed in apparently healthy 496 middle-aged to elderly persons recruited consecutively among the visitors to the medical check-up program, Anti-Aging Doc, in a University hospital, from March 2006 to December 2007. Mid-thigh muscle cross-sectional area (CSA) was measured by computed tomography and corrected by body weight (CSA/BW). Carotid intima–media thickness (IMT) and brachial–ankle pulse wave velocity (baPWV) were measured. ResultsThigh muscle CSA/BW was significantly and negatively associated with carotid IMT and baPWV in men but not in women. After correction for other confounding parameters, baPWV was an independent risk for the presence of sarcopenia in men (odds ratio of 1m/s increase of baPWV=1.14, 95% CI=1.01–1.30, p<0.05) in addition to age, body height, low physical activity, free testosterone level. Conversely, thigh muscle CSA/BW was an independent determinant of baPWV (β=−0.15, p<0.01) in addition to age, blood pressure, triglyceride, and antihypertensive drug use in men. ConclusionsArterial stiffness is related to thigh muscle volume in men. Sarcopenia and atherosclerosis may share a common pathway and interact with each other to facilitate mutual abnormalities.

Effects of Aerobic Exercise on Abdominal Fat, Thigh Muscle Mass and Muscle Strength in Type 2 Diabetic Subject

BackgroundAerobic exercise can effectively reduce visceral fat. However, few studies have examined the effect of daily physical activity on obesity and cardiopulmonary function in the subjects with diabetes. We examined the effect of moderate intensity of walking in obese diabetes patients by monitoring of daily activity and measuring the change in abdominal fat area, muscle are and maximal muscle strength.MethodsWe randomly assigned 27 obese women with type 2 diabetes to an aerobic exercise group (AG, n = 13) and control group (CG, n = 14). The AG performed moderate intensity walking for 60 minutes per exercise, 5 times per week, and for 12 weeks. The activity energy expenditure was monitored by a multi-record accelerometer. The CG maintained routine daily activities. At the time of the initiation of the study and after 12 weeks of exercise, the aerobic exercise capacity was assessed using oxygen consumption rate at anaerobic threshold (VO2-AT). The abdominal fat area and the quadriceps muscle area were measured by computed tomography, and the maximum muscle strength of the upper and lower limbs was measured by a chest press and a leg press, respectively.ResultsThe mean age of the study subjects was 56.6 ± 8.0 years, the mean duration of diabetes was 6.3 ± 6.0 years, and the body weight index (BMI) was 27.3 ± 2.7 kg/m2. The BMI of the AG was significantly decreased (P = 0.003). In the AG, the visceral fat area and subcutaneous fat area were also significantly decreased (P = 0.018 and P < 0.001, respectively) but not in CG. VO2-AT of the AG was significantly improved, while that of the CG did not change (P = 0.009 and P = 0.115, respectively). The quadriceps muscle mass and the maximal muscle strength of the AG did not change, however, the CG showed a significant decrease. Duration of moderate intensity exercise was correlated with the decrease in total abdominal fat area (r = -0.484; P = 0.011) and that of high intensity exercise was correlated with improvement of cardiopulmonary function (r = 0.414; P = 0.032).ConclusionDaily moderate intensity aerobic exercise is effective at reducing abdominal fat mass, while high intensity exercise improves cardiopulmonary function.

Peak Growth Hormone-Releasing Hormone-Arginine-Stimulated Growth Hormone Is Inversely Associated with Intramyocellular and Intrahepatic Lipid Content in Premenopausal Women with Obesity

Visceral adiposity is a strong determinant of GH secretion, and low endogenous GH secretion is associated with increased insulin resistance, a key component of the metabolic syndrome. Increased fat accumulation in skeletal muscle and liver may play an etiological role in the development of insulin resistance and other complications of the metabolic syndrome. Little is known about the role of decreased endogenous GH secretion in the pathogenesis of insulin resistance in obesity. To investigate the relationship between intramyocellular lipids (IMCL), intrahepatic lipids, and peak-stimulated GH in premenopausal women with obesity. We conducted a cross-sectional study at a clinical translational research center. Patients included 21 premenopausal women with obesity (mean body mass index, 34.0 +/- 4.5 kg/m(2)) and 17 normal-weight controls (mean body mass index, 21.9 +/- 2.0 kg/m(2)) of comparable mean age. IMCL and intrahepatic lipids were measured with proton magnetic resonance spectroscopy ((1)H-MRS). Body composition was measured with magnetic resonance imaging. Peak GH was measured after stimulation with GHRH-arginine. Obese subjects had higher IMCL, intrahepatic lipids, abdominal and thigh fat, and thigh muscle mass compared with normal-weight controls. There were strong inverse associations between peak GH and both IMCL and intrahepatic lipids independent of age and visceral adiposity. There were positive associations between IMCL and intrahepatic lipids with measures of insulin resistance and serum triglycerides. In premenopausal women with obesity, peak GH is inversely associated with IMCL and intrahepatic lipids independent of age and visceral adiposity. This suggests that low GH may contribute to insulin resistance in obesity through effects on muscle and intrahepatic lipids.

Circulating soluble transferrin receptor concentration decreases after exercise-induced improvement of insulin sensitivity in obese individuals

Circulating soluble transferrin receptor (sTfR) has been recently found to be associated negatively with insulin sensitivity. To evaluate circulating sTfR concentration after changing insulin sensitivity in obese individuals. Circulating sTfR concentration was evaluated after diet-induced weight loss in obese women (diet (D) group, n=8); after diet-induced weight loss plus resistance training (D+RT group, n=11); and after follow-up without weight loss (control (C) group, n=7). After 16 weeks, insulin sensitivity (HOMA (Homeostasis Model Assessment) value) significantly improved in parallel to weight loss (-7.3%) and reduced total fat mass (evaluated using magnetic resonance imaging) in the D group. Thigh muscle mass decreased significantly (P=0.03). Serum sTfR concentration did not change significantly. In the D+RT group, weight loss (-8.7%) and improvement of insulin sensitivity were of similar magnitude. Thigh muscle mass was preserved (P=0.8). Serum sTfR concentration decreased significantly (P=0.001). Interestingly, higher the thigh muscle volume after weight loss, higher the decrease in circulating sTfR concentration. We also found that higher the increases in leg force at week 16, higher the decrease in circulating sTfR concentration in all individuals as a whole. No significant changes were observed in insulin sensitivity, sTfR concentration or thigh muscle mass in the C group. These findings suggest a long-term regulation of serum sTfR concentration by exercise-induced improvement of insulin sensitivity in obese individuals.

Blood‐flow fluctuation during light‐resistance exercise may enhance the effectiveness of high‐protein snack on the increase of muscle mass and strength

We have demonstrated the preventive effects of a high‐protein snack 3hrs after a basal mealunder voluntary tower climbing exercise on the loss of muscle and bone mass in aging‐model rats receiving glucocorticoid injections. However, this "missile nutrition" effects of the snack could no be observed without exercise. In this study we examined chronic effects of light‐resistance exercise (15‐min dumbbell exercise using 300g brown‐rice filled dmbbells) after a high‐protein (15g)‐sucrose (15g) snack (HPS) on the forearm and thigh muscle mass and hand‐grip and leg‐extension strength, comparing with that of exercise or HPS alone in young adults. Neither dumbbell exercise nor HPS alone increased muscle mass and strength, excepting a significant increase of hand‐grip strength with exercise. Contrarily, both muscle mass and strength in either forearm or thigh muscle was significantly increased and body fat mass was significantly decreased by the intake of HPS followed by dumbbell exercise 45 min after HPS ingestion. The dumbbell exercise fluctuated greately the blood flow in the muscle tisues and lowered the peaked plasma amino acid concentrations after HPS, suggesting an enhanced amino acid uptake by the muscle to effective protein synthesis.

The Relationship of Serum Osteocalcin Concentration to Insulin Secretion, Sensitivity, and Disposal with Hypocaloric Diet and Resistance Training

Bone has recently been described as exhibiting properties of an endocrine organ by producing osteocalcin that increases insulin sensitivity and secretion in animal models. We aimed to evaluate circulating osteocalcin in association with insulin sensitivity and insulin secretion in three different studies in nondiabetic subjects: one cross-sectional study in 149 men (using minimal model), and two longitudinal studies in two independent groups (one formed by 26 women, and the other by 9 men and 11 women), after a mean of 7.3 and 16.8% weight loss, and after a mean of 8.7% weight loss plus regular exercise. In the cross-sectional study, circulating osteocalcin was associated with insulin sensitivity, mainly in lean subjects, and with insulin secretion (only in lean subjects). A mean of 16.8%, but not 7.3% weight loss, led to significant increases in circulating osteocalcin. However, a mean of 8.7% weight loss plus regular exercise led to the more pronounced effects on the serum osteocalcin concentration, which increased in parallel to reduced visceral fat mass, unchanged thigh muscle mass, and increased leg strength and force. The postintervention serum levels of osteocalcin were associated with both insulin sensitivity (r = 0.49; P = 0.03) and fasting triglycerides (r = -0.54; P = 0.01). The change in visceral fat was the parameter that best predicted the change in serum osteocalcin, once age, body mass index, and insulin sensitivity changes were controlled for (P = 0.002). Circulating osteocalcin could mediate the role of bone as an endocrine organ in humans.

The reduction in visceral fat mass in response to growth hormone is more marked in men than in oestrogen-deficient women

Context Women with severe growth hormone (GH) deficiency have a less marked response to GH replacement than men. This has mostly been attributed to the attenuating effects of oestrogen replacement therapy. Objective To study gender related differences in the response to GH treatment in men and postmenopausal women. Methods Fifteen men and 15 age- and BMI-matched women with abdominal obesity (mean age: 58; range 51–64 years) were treated for one year with similar doses (0.47 vs. 0.51 mg/day) of GH. All women were postmenopausal not receiving oestrogen treatment. Insulin sensitivity was assessed using a hyperinsulinemic euglycemic clamp and body composition by computed tomography (CT) scans and from total body potassium, K 40. Results Men and women were comparable at baseline in terms of waist circumference, IGF-1 and lipid levels. After one year of GH treatment, there was a 18% reduction in visceral adipose tissue (VAT) in men and a 5% reduction in women ( P = 0.0001 men vs. women). Although the magnitude of the difference was small, men increased more in thigh muscle mass ( P < 0.0001 vs. women). A reduction in thigh intermuscular adipose tissue (IMAT) and diastolic blood pressure was seen only in men (both p < 0.05 vs. baseline). A decrease in LDL cholesterol, and an increase in serum insulin, was observed only in women (both p < 0.05 vs. baseline). Conclusion Low dose GH treatment reduced VAT more markedly in men as compared with women. As all women were postmenopausal and oestrogen-deficient, this gender difference in responsiveness was not due to an antagonistic effect of oestrogen on peripheral GH action.

Estimation of Thigh Muscle Mass With Magnetic Resonance Imaging in Older Adults and People With Chronic Obstructive Pulmonary Disease

Quantifying muscle mass is an essential part of physical therapy assessment, particularly in older adults and in people with chronic conditions associated with muscle atrophy. The purposes of this study were to examine the relationship between muscle cross-sectional area (CSA) and volume by use of magnetic resonance imaging (MRI) and to compare anthropometric estimations of midthigh CSA with measurements obtained from MRI. Twenty older adults who were healthy and 20 people with chronic obstructive pulmonary disease (COPD), matched for age, sex, and body mass index, underwent MRI to obtain measurements of thigh muscle CSA and volume. Anthropometric measurements (skinfold thickness and thigh circumference) were used to estimate midthigh CSA. Muscle volumes were significantly lower in the people with COPD than in the older adults who were healthy. Moderate to high correlations were found between midthigh CSA and volume in both groups (r=.61-.94). Anthropometric measurements tended to overestimate midthigh CSA in both the people with COPD (estimated CSA=64.9+/-17.8; actual CSA=48.3+/-10.2 cm(2)) and the older adults who were healthy (estimated quadriceps femoris muscle CSA=65.0+/-14.0; actual CSA=56.8+/-13.5 cm(2)). Furthermore, the estimated quadriceps femoris muscle CSAs were not sensitive enough to detect a difference in muscle size between people with COPD and controls. Thigh circumference alone was not different between groups and showed only low to moderate correlations with muscle volume (r=.19-.47). Muscle CSA measured from a single slice provides a good indication of volume, but the most representative slice should be chosen on the basis of the muscle group of interest. Thigh circumference is not correlated with muscle volume and, therefore, should not be used as an indicator of muscle size. The development of population-specific reference equations for estimating muscle CSA from anthropometric measurements is warranted.

Estimation of thigh muscle cross-sectional area by dual-energy X-ray absorptiometry in frail elderly patients

Background: Thigh muscle mass and cross-sectional area (CSA) are useful indexes of sarcopenia and the response to treatment in older patients. Current criterion methods are computed tomography (CT) and magnetic resonance imaging.Objective: The objective was to compare thigh muscle mass estimated by dual-energy X-ray absorptiometry (DXA), a less expensive and more accessible method, with thigh muscle CSA determined by CT in a group of elderly patients recovering from hip fracture.Design: Midthigh muscle CSA (in cm2) was assessed from a 1-mm CT slice and midthigh muscle mass (g) from a 1.3-cm DXA slice in 30 patients (24 women) aged 81 ± 8 y during 12 mo of follow-up. Fat-to-lean soft tissue ratios were calculated with each technique to permit direct comparison of a variable in the same units.Results: Baseline midthigh muscle CSA was highly correlated with midthigh muscle mass (r = 0.86, P < 0.001) such that DXA predicted CT-determined CSA with an SEE of 10 cm2 (an error of ≈12% of the mean CSA value). CT- and DXA-determined ratios of midthigh fat to lean mass were similarly related (intraclass correlation coefficient = 0.87, P < 0.001). When data were expressed as the changes from baseline to follow-up, CT and DXA changes were weakly correlated (intraclass correlation coefficient = 0.51, P = 0.019).Conclusions: Assessment of sarcopenia by DXA midthigh slice is a potential low-radiation, accessible alternative to CT scanning of older patients. The errors inherent in this technique indicate, however, that it should be applied to groups of patients rather than to individuals or to evaluate the response to interventions.

Can dual energy X-ray absorptiometry provide a valid assessment of changes in thigh muscle mass with strength training in older adults?

To determine how dual-energy X-ray absorptiometry (DXA) compares to computed tomography (CT) for measuring changes in total thigh skeletal muscle (SM) mass with strength training (ST) in older adults. Fifty previously sedentary, relatively healthy older men (n=23, 60 (s.d.=7.5) years) and women (n=27, 60 (s.d.=9.3) years). Results indicate that there was a significant increase in thigh SM mass with ST measured by both CT (3.9+/-0.4%) and DXA (2.9+/-0.6%) methods (both P<0.001), and there was not a significant difference in percent change between the two methods, although there was a substantial absolute difference ( approximately 2 kg) at baseline between the two methods. Although Bland-Altman plots indicate overall agreement between the percent thigh SM mass changes of DXA vs CT methods, the 3.4% error associated with DXA was greater than the thigh SM mass change from DXA. However, the CT measured change in thigh SM mass was greater than its error (0.6%). DXA overestimates baseline and after ST thigh SM mass, and may not be able to detect small changes in thigh SM mass with ST due to its higher error. Although DXA has certain advantages that warrant is used in epidemiologic and intervention studies, improvements to DXA are needed for the accurate assessment of small changes in thigh SM mass.

Hip, thigh and calf muscle atrophy and bone loss after 5-week bedrest inactivity

Unloaded inactivity induces atrophy and functional deconditioning of skeletal muscle, especially in the lower extremities. Information is scarce, however, regarding the effect of unloaded inactivity on muscle size and function about the hip. Regional bone loss has been demonstrated in hips and knees of elderly orthopaedic patients, as quantified by computerized tomography (CT). This method remains to be validated in healthy individuals rendered inactive, including real or simulated weightlessness. In this study, ten healthy males were subjected to 5 weeks of experimental bedrest and five matched individuals served as ambulatory controls. Maximum voluntary isometric hip and knee extension force were measured using the strain gauge technique. Cross-sectional area (CSA) of hip, thigh and calf muscles, and radiological density (RD) of the proximal tibial bone were measured using CT. Bedrest decreased (P < 0.05) average (SD) muscle strength by 20 (8)% in knee extension, and by 22 (12)% in hip extension. Bedrest induced atrophy (P < 0.05) of extensor muscles in the gluteal region, thigh and calf, ranging from 2 to 12%. Atrophy was more pronounced in the knee extensors [9 (4)%] and ankle plantar flexors [12 (3)%] than in the gluteal extensor muscles [2 (2)%]. Bone density of the proximal tibia decreased (P < 0.05) by 3 (2)% during bedrest. Control subjects did not show any temporal changes in muscle or bone indices (P > 0.05), when examined at similar time intervals. The present findings of a substantial loss in hip extensor strength and a smaller, yet significant atrophy of these muscles, demonstrate that hip muscle deconditioning accompanies losses in thigh and calf muscle mass after bedrest. This suggests that comprehensive quantitative studies on impaired locomotor function after inactivity should include all joints of the lower extremity. Our results also demonstrate that a decreased RD, indicating bone mineral loss, can be shown already after 5 weeks of unloaded bedrest, using a standard CT technique.

The Effect Of Gender On Absolute And Relative Peak Power

PURPOSE: There is speculation that men and women have similar lower body power when controlling for body weight and cross-sectional area (CSA). The purpose of this study was to evaluate the effects of gender and body mass on absolute and relative peak power. METHODS: Sixty male (n=25) and female (n=35) university kinesiology students (age23.13±2.11 yrs, height 170.94±10.68 cm, weight 71.19±5.34 kg) performed 3 maximal concentric knee extension repetitions on an isokinetic dynamometer at 15 random speeds between 30 and 500 d/s. Muscle CSA was estimated via the Housh equation derived from the anterior thigh skinfold and circumference. Differences between males and females were determined at each speed using ANOVA. RESULTS: Males were significantly heavier (males=81.51±11.64 kg; females=63.83 ± 13.34 kg) and had greater thigh CSA (males=143.12±18.17 cm2; females 114.55 ± 21.56 cm2) than females. Males also demonstrated significantly (p <0.05) greater power across all speeds when compared to females in terms of absolute peak power (males=119.20±27.18;females=81.06±21.09 at 30d/s, males=792.54±192.68; females=531.41±107.07 at 500 d/s), peak power relative to body weight (males=1.47±0.27W/kg; females=1.27±0.26W/kg at 30d/s, males=9.66±2.17 W/kg; females=8.04±1.32 W/kg at 500 d/s), and peak power relative to CSA (males=1.61±0.26W/cm2; females=1.43±0.28 W/cm2 at 30 d/s, males=10.52±1.89 W/cm2; females=8.75±1.21 W/cm2 at 500 d/s). CONCLUSION: These results demonstrate that the greater body mass or thigh muscle mass of males may not completely explain power differences between genders. Although body size plays a large role in power expression, other factors must be influencing the male bias such as neuromuscular efficiency or female inhibition.

Effects Of Training Experience On The Relationship Between Muscle Mass And Isometric Force Production

PURPOSE The purpose of this study was to compare the relationship between thigh muscle mass and isometric force production in college-aged males of different training levels. METHODS A group of highly trained (HT) weightlifters (n=11, 20.5 ± 0.4 years, 171.9 ± 2.8 cm, 89.5 ± 7.6 kg) was compared with a group of recreationally trained (RT) college students (n=16, 23.0 ± 0.5 years, 185.2 ± 1.8 cm, 84.2 ± 3.2 kg). The HT group included national-level collegiate weightlifters with 6.1 ± 0.3 years of competition training experience. Subjects were assessed for isometric peak force (ISOPF) of the knee extensors, while thigh muscle mass was determined from total body DXA scans with specific region of interest measurements. RESULTS There were no significant differences (p>0.05) between the HT and RT groups for body weight, total thigh mass, or bone-free lean thigh mass (LT), however, the RT group was significantly older and taller (p<0.001) than the HT group. ISOPF for the HT group was significantly greater (p<0.001) than the RT group (305.1 ± 30.2 nm vs. 187.4 ± 17.4 nm). Analysis of correlation coefficients determined a strong, significant correlation between ISOPF and LT in the HT group (r=0.83, p<0.01), while only a weak relationship existed in the RT group (r=0.15). Adjusting ISOPF for LT mass, resulted in a highly significant difference (p<0.005) between the HT and RT groups (4.27 ± 0.24 vs. 3.02 ± 0.29). ISOPF, when controlling for LT, was also significantly higher (p=0.001) for the HT group, as determined by univariate ANCOVA. CONCLUSIONS Previous research suggests a relationship between lean muscle mass and the ability to produce force. The results of this study determined that lean thigh mass is only partially responsible for the significant difference in ISOPF between the HT and RT group, suggesting the ability to produce force is dependant upon many factors besides the amount of muscle mass involved in a given effort. Possible neuromuscular factors, including motor unit recruitment and activation, may be improved with chronic training; thus allowing the HT group to take full advantage of their LT.

Effects Of Training Experience On The Relationship Between Muscle Mass And Isometric Force Production

PURPOSE The purpose of this study was to compare the relationship between thigh muscle mass and isometric force production in college-aged males of different training levels. METHODS A group of highly trained (HT) weightlifters (n=11, 20.5 ± 0.4 years, 171.9 ± 2.8 cm, 89.5 ± 7.6 kg) was compared with a group of recreationally trained (RT) college students (n=16, 23.0 ± 0.5 years, 185.2 ± 1.8 cm, 84.2 ± 3.2 kg). The HT group included national-level collegiate weightlifters with 6.1 ± 0.3 years of competition training experience. Subjects were assessed for isometric peak force (ISOPF) of the knee extensors, while thigh muscle mass was determined from total body DXA scans with specific region of interest measurements. RESULTS There were no significant differences (p>0.05) between the HT and RT groups for body weight, total thigh mass, or bone-free lean thigh mass (LT), however, the RT group was significantly older and taller (p<0.001) than the HT group. ISOPF for the HT group was significantly greater (p<0.001) than the RT group (305.1 ± 30.2 nm vs. 187.4 ± 17.4 nm). Analysis of correlation coefficients determined a strong, significant correlation between ISOPF and LT in the HT group (r=0.83, p<0.01), while only a weak relationship existed in the RT group (r=0.15). Adjusting ISOPF for LT mass, resulted in a highly significant difference (p<0.005) between the HT and RT groups (4.27 ± 0.24 vs. 3.02 ± 0.29). ISOPF, when controlling for LT, was also significantly higher (p=0.001) for the HT group, as determined by univariate ANCOVA. CONCLUSIONS Previous research suggests a relationship between lean muscle mass and the ability to produce force. The results of this study determined that lean thigh mass is only partially responsible for the significant difference in ISOPF between the HT and RT group, suggesting the ability to produce force is dependant upon many factors besides the amount of muscle mass involved in a given effort. Possible neuromuscular factors, including motor unit recruitment and activation, may be improved with chronic training; thus allowing the HT group to take full advantage of their LT.