Home About us Contact
|
Home About us Contact | ||
|
|
||
Muscle Cross-sectional Area (muscle + cross-sectional_area)
Selected AbstractsBone Mineral Content per Muscle Cross-Sectional Area as an Index of the Functional Muscle-Bone Unit,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2002Eckhard Schoenau M.D. Abstract Bone densitometric data often are difficult to interpret in children and adolescents because of large inter- and intraindividual variations in bone size. Here, we propose a functional approach to bone densitometry that addresses two questions: Is bone strength normally adapted to the largest physiological loads, that is, muscle force? Is muscle force adequate for body size? To implement this approach, forearm muscle cross-sectional area (CSA) and bone mineral content (BMC) of the radial diaphysis were measured in 349 healthy subjects from 6 to 19 years of age (183 girls), using peripheral quantitative computed tomography (pQCT). Reference data were established for height-dependent muscle CSA and for the variation with age in the BMC/muscle CSA ratio. These reference data were used to evaluate results from three pediatric patient groups: children who had sustained multiple fractures without adequate trauma (n = 11), children with preterminal chronic renal failure (n = 11), and renal transplant recipients (n = 15). In all three groups mean height, muscle CSA, and BMC were low for age, but muscle CSA was normal for height. In the multiple fracture group and in renal transplant recipients the BMC/muscle CSA ratio was decreased (p < 0.05), suggesting that bone strength was not adapted adequately to muscle force. In contrast, chronic renal failure patients had a normal BMC/muscle CSA ratio, suggesting that their musculoskeletal system was adapted normally to their (decreased) body size. This functional approach to pediatric bone densitometric data should be adaptable to a variety of densitometric techniques. [source] Soleus T reflex modulation in response to spinal and tendinous adaptations to unilateral lower limb suspension in humansACTA PHYSIOLOGICA, Issue 3 2008O. R. Seynnes Abstract Aim:, To investigate the influence of tendinous and synaptic changes induced by unilateral lower limb suspension (ULLS) on the tendon tap reflex. Methods:, Eight young men underwent a 23-day period of ULLS. Muscle cross-sectional area (CSA), torque and electromyographic (EMG) activity of the plantar flexor muscles (normalized to the M wave), Achilles tendon,aponeurosis mechanical properties, soleus (SOL) H and T reflexes and associated peak twitch torques were measured at baseline, after 14 and 23 days of ULLS, and 1 week after resuming ambulatory activity. Results:, Significant decreases in muscle CSA (,9%), in maximal voluntary torque (,10%) and in the associated SOL EMG activity (,16%) were found after ULLS (P < 0.05). In addition to a 36% (P < 0.01) decrease in tendon,aponeurosis stiffness, normalized H reflex increased by 35% (P < 0.05). An increase in the slope (28%, P < 0.05) and intercept (85%, P < 0.05) of the T reflex recruitment curve pointed to an increase in the gain and to a decrease in the sensitivity of this reflex, possibly resulting from the decrease in the tendon,aponeurosis stiffness at low forces. Following ULLS, changes in tendinous stiffness correlated with changes in neuromuscular efficiency (peak twitch torque to reflex ratio) at higher tendon tap forces. Conclusion:, These findings point out the dual and antagonistic influences of spinal and tendinous adaptations upon the tendon tap reflex in humans under conditions of chronic unloading. These observations have potential implications for the sensitivity of the short-latency Ia stretch response involved in rapid compensatory contractions to unexpected postural perturbations. [source] Greater growth hormone and insulin response in women than in men during repeated bouts of sprint exerciseACTA PHYSIOLOGICA, Issue 2 2009M. Esbjörnsson Abstract Aim:, In a previous study, sprint training has been shown to increase muscle cross-sectional area in women but not in men [Eur J Appl Physiol Occup Physiol 74 (1996) 375]. We hypothesized that sprint exercise induces a different hormonal response in women than in men. Such a difference may contribute to explaining the observed gender difference in training response. Method:, Metabolic and hormonal response to three 30-s sprints with 20-min rest between the sprints was studied in 18 physically active men and women. Results:, Accumulation of blood lactate [interaction term gender (g) × time (t): P = 0.022], and plasma ammonia (g × t: P < 0.001) after sprint exercise was greater in men. Serum insulin increased after sprint exercise more so in women than in men (g × t: P = 0.020), while plasma glucose increased in men, but not in women (g × t: P < 0.001). Serum growth hormone (GH) increased in both women and men reaching similar peak levels, but with different time courses. In women the peak serum GH level was observed after sprint 1, whereas in men the peak was observed after sprint 3 (g × t; P < 0.001). Serum testosterone tended to decrease in men and increase in women (g × t: P = 0.065). Serum cortisol increased approx. 10,15% after sprint exercise, independent of gender (time: P = 0.005). Conclusion:, Women elicited a greater response of serum GH and insulin to sprint exercise. This may contribute to explaining the earlier observed muscle hypertrophy in women in response to sprint training. [source] Computed tomographic measurements of thigh muscle cross-sectional area and attenuation coefficient predict hip fracture: The health, aging, and body composition studyJOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2010Thomas Lang Abstract Fatty infiltration of muscle, myosteatosis, increases with age and results in reduced muscle strength and function and increased fall risk. However, it is unknown if increased fatty infiltration of muscle predisposes to hip fracture. We measured the mean Hounsfield unit (HU) of the lean tissue within the midthigh muscle bundle (thigh muscle HU, an indicator of intramuscular fat), its cross-sectional area (CSA, a measure of muscle mass) by computed tomography (CT), bone mineral density (BMD) of the hip and total-body percent fat by dual X-ray absorptiometry (DXA), isokinetic leg extensor strength, and the Short Physical Performance Battery (SPPB) in 2941 white and black women and men aged 70 to 79 years. Sixty-three hip fractures were validated during 6.6 years of follow-up. Proportional hazards regression analysis was used to assess the relative risk (RR) of hip fracture across variations in thigh muscle attenuation, CSA, muscle strength, and physical function for hip fracture. In models adjusted by age, race, gender, body mass index, and percentage fat, decreased thigh muscle HU resulted in increased risk of hip fracture [RR/SD,=,1.58; 95% confidence interval (CI) 1.10,1.99], an association that continued to be significant after further adjustment for BMD. In models additionally adjusted by CSA, muscle strength, and SPPB score, decreased thigh muscle HU but none of the other muscle parameters continued to be associated with an increased risk of hip fracture (RR/SD,=,1.42; 95% CI 1.03,1.97). Decreased thigh muscle HU, a measure of fatty infiltration of muscle, is associated with increased risk of hip fracture and appears to account for the association between reduced muscle strength, physical performance, and muscle mass and risk of hip fracture. This characteristic captures a physical characteristic of muscle tissue that may have importance in hip fracture etiology. © 2010 American Society for Bone and Mineral Research [source] Bone Mineral Content per Muscle Cross-Sectional Area as an Index of the Functional Muscle-Bone Unit,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2002Eckhard Schoenau M.D. Abstract Bone densitometric data often are difficult to interpret in children and adolescents because of large inter- and intraindividual variations in bone size. Here, we propose a functional approach to bone densitometry that addresses two questions: Is bone strength normally adapted to the largest physiological loads, that is, muscle force? Is muscle force adequate for body size? To implement this approach, forearm muscle cross-sectional area (CSA) and bone mineral content (BMC) of the radial diaphysis were measured in 349 healthy subjects from 6 to 19 years of age (183 girls), using peripheral quantitative computed tomography (pQCT). Reference data were established for height-dependent muscle CSA and for the variation with age in the BMC/muscle CSA ratio. These reference data were used to evaluate results from three pediatric patient groups: children who had sustained multiple fractures without adequate trauma (n = 11), children with preterminal chronic renal failure (n = 11), and renal transplant recipients (n = 15). In all three groups mean height, muscle CSA, and BMC were low for age, but muscle CSA was normal for height. In the multiple fracture group and in renal transplant recipients the BMC/muscle CSA ratio was decreased (p < 0.05), suggesting that bone strength was not adapted adequately to muscle force. In contrast, chronic renal failure patients had a normal BMC/muscle CSA ratio, suggesting that their musculoskeletal system was adapted normally to their (decreased) body size. This functional approach to pediatric bone densitometric data should be adaptable to a variety of densitometric techniques. [source] Muscle Cellularity at Cranial and Caudal Levels of the Trunk Musculature of Commercial Size Sea Bass, Dicentrarchus labrax (Linnaeus, 1758)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2005I. Abdel Summary In eight specimens of Atlantic sea bass of commercial size (,350 g) muscle cellularity was studied at two selected sampling levels of the trunk axial musculature: caudal (anal opening) and cranial (fourth radius of the dorsal fin). The following parameters were quantified at both sampling levels: white muscle cross-sectional area, white muscle fibre diameter (900,1200 fibres), muscle fibre number and muscle fibre density. Results showed a higher total cross-sectional area at cranial than at caudal level (P < 0.05), what is related with their different gross morphology. However, the white muscle fibre size distribution, as well as the muscle fibre number and density did not show significant differences between them. This study contributes to typify muscle fibre sampling in sea bass of commercial size what is of great interest for morphometric studies where white muscle cellularity is commonly correlated with textural or organoleptic parameters. [source] Comparative effects of resistance training on peak isometric torque, muscle hypertrophy, voluntary activation and surface EMG between young and elderly womenCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2007Jack Cannon Summary We compared the effect of a 10-week resistance training program on peak isometric torque, muscle hypertrophy, voluntary activation and electromyogram signal amplitude (EMG) of the knee extensors between young and elderly women. Nine young women (YW; range 20,30 years) and eight elderly women (EW; 64,78 years) performed three sets of ten repetitions at 75% 1 repetition maximum for the bilateral leg extension and bilateral leg curl 3 days per week for 10 weeks. Peak isometric torque, EMG and voluntary activation were assessed before, during, and after the training period, while knee extensor lean muscle cross-sectional area (LCSA) and lean muscle volume (LMV) were assessed before and after the training period only. Similar increases in peak isometric torque (16% and 18%), LCSA (13% and 12%), LMV (10% and 9%) and EMG (19% and 21%) were observed between YW and EW, respectively, at the completion of training (P<0·05), while the increase in voluntary activation in YW (1·9%) and EW (2·1%) was not significant (P>0·05). These findings provide evidence to indicate that participation in regular resistance exercise can have significant neuromuscular benefits in women independent of age. The lack of change in voluntary activation following resistance training in both age groups despite the increase in EMG may be related to differences between measurements in their ability to detect resistance training-induced changes in motor unit activity. However, it is possible that neural adaptation did not occur and that the increase in EMG was due to peripheral adaptations. [source] | |||||||||||||