Calf Cross-sectional Area Research Articles

ASSOCIATION BETWEEN CALF MUSCLE FATTY INFILTRATION AND PHYSICAL PERFORMANCE AMONG HEALTHY OLDER ADULTS

Abstract Muscle fatty infiltration is associated with impaired physical performance. However, the association between ectopic fat, such as lower extremity fat distribution, and sex-specific differences among older adults remains to be determined. This study aimed to examine sex-specific differences in calf muscle fat infiltration and their association with physical performance among healthy older adults aged 76 to 80 years. The pilot study comprised 40 subjects (20 men; 20 women) matched by age and body mass index. The participants underwent dual-energy X-ray absorptiometry, magnetic resonance imaging (MRI), and proton magnetic resonance spectroscopy (1H-MRS) to assess body composition and lower extremity fat distribution. The tibialis anterior intramyocellular lipid (IMCL) as assessed by 1H-MRS was negatively associated with the five-times sit-to-stand test scores (rs=0.518, p=0.023) in men, while the soleus IMCL content was negatively associated with the timed up-and-go test scores (rs=0.472, p=0.048) in women. However, the soleus extramyocellular lipid (EMCL) content was positively associated with the five-times sit-to-stand test scores (rs=−0.488, p=0.040) in women, but this association was not statistically significant in men. Regarding the calf cross-sectional area (CSA) parameters assessed by MRI, calf subcutaneous fat CSA was positively associated with the usual gait speed (rs=0.447, p=0.048) in women only. To conclude, this study showed an inverse correlation between IMCL content and physical performance in healthy older individuals and calf muscle-specific IMCL based on sex differences. Furthermore, our results suggest that greater EMCL content in the soleus and calf subcutaneous fat might affect physical performance positively in older women but not older men.

Position of compression garment around the knee affects healthy adults’ knee joint position sense acuity

Athletes use compression garments (CGs) to improve sport performance, accelerate rehabilitation from knee injuries or to enhance joint position sense (JPS). The position of CGs around the knee may affect knee JPS but the data is inconsistent. The purpose of the present study was to determine the effects of CG position on healthy adults’ knee joint position sense acuity. In a counterbalanced, single-blinded study, 16 healthy young adults (8 female, age: 25.5 y) performed an active knee joint position-matching task with and without (CON) a below-knee (BK), above-knee (AK), or whole-knee (WK) CG in a randomized order on the dominant (CompDom) or the non-dominant leg (CompNon-Dom). We also determined the magnitude of tissue compression by measuring anatomical thigh and calf cross sectional area (CSA) in standing using magnetic resonance imaging (MRI). Subjects had less absolute repositioning error (magnitude of error) in BK compared with CON condition. On the other hand, the analysis of the direction of error (constant error) revealed that in each condition subjects tended to underestimate the target position (AK, BK and CON: 75%; WK: 94%). In WK condition there was a significantly larger negative error (−2.7 ± 3.4) as compared with CON (−1.6 ± 3.7) condition. There also was less variable error, in WK compared to BK and CON conditions, indicating less variability in their position sense using a WK CG, regardless of the underestimation. CG reduced thigh CSA by 4.5 cm2 or 3% and calf CSA by Δ1.3 cm2 or 1%. The position of CG relative to the knee modifies knee JPS. The findings helps us better understand how the application of a WK CG may support athletic activities.

Lower limb neuromuscular function and blood flow characteristics in AFO-using survivors of stroke.

Ankle-foot orthoses (AFOs) and gait aids are commonly used by survivors of stroke to ambulate, but they have not been used as inclusion or exclusion criteria for physiological studies. The purpose of this study was to examine differences in neuromuscular function and blood flow characteristics between the lower limbs of ambulatory, AFO-using survivors of stroke (n = 9). The subjects were, on average, 14 years poststroke and had used an AFO for about 7 years. We used the following measures to assess both lower limbs: quadriceps muscular strength (manual muscle testing, 1RM), calf muscular endurance (single-leg heel raises), lower limb soft tissue composition and muscle cross-sectional area, calf resting blood flow (strain gauge plethysmography), and central neural drive of the plantar flexors (nerve stimulation). The sound limb was defined as the control. Quadriceps strength, triceps surae endurance, and calf cross-sectional area all were greater in the sound limb than in the affected limb (relative differences: 76.3% ± 16.6%, 146.4% ± 24.6%, and 25.6% ± 5.7%, respectively). In addition, resting blood flow, peak torque, and central neural drive of the plantar flexors were significantly greater (relative differences: 38.7% ± 5.9%, 94.4% ± 17.9%, and 43.6% ± 12.0%, respectively) in the sound calf. Our findings confirm that significant decrements in muscle performance, size, and blood flow persist in the affected limb many years after stroke despite a resumption of ambulation. This cohort of ambulatory AFO users exhibited large variations in functional abilities. We recommend that future studies in stroke survivors consider AFO use in their research designs.

Influence of vibration resistance training on knee extensor and plantar flexor size, strength, and contractile speed characteristics after 60 days of bed rest

Spaceflight and bed rest (BR) result in loss of muscle mass and strength. This study evaluated the effectiveness of resistance training and vibration-augmented resistance training to preserve thigh (quadriceps femoris) and calf (triceps surae) muscle cross-sectional area (CSA), isometric maximal voluntary contraction (MVC), isometric contractile speed, and neural activation (electromyogram) during 60 days of BR. Male subjects participating in the second Berlin Bed Rest Study underwent BR only [control (CTR), n = 9], BR with resistance training (RE; n = 7), or BR with vibration-augmented resistance training (RVE; n = 7). Training was performed three times per week. Thigh CSA and MVC torque decreased by 13.5 and 21.3%, respectively, for CTR (both P < 0.001), but were preserved for RE and RVE. Calf CSA declined for all groups, but more so (P < 0.001) for CTR (23.8%) than for RE (10.7%) and RVE (11.0%). Loss in calf MVC torque was greater (P < 0.05) for CTR (24.9%) than for RVE (12.3%), but not different from RE (14.8%). Neural activation at MVC remained unchanged in all groups. For indexes related to rate of torque development, countermeasure subjects were pooled into one resistance training group (RT, n = 14). Thigh maximal rate of torque development (MRTD) and contractile impulse remained unaltered for CTR, but MRTD decreased 16% for RT. Calf MRTD remained unaltered for both groups, whereas contractile impulse increased across groups (28.8%), despite suppression in peak electromyogram (12.1%). In conclusion, vibration exposure did not enhance the efficacy of resistance training to preserve thigh and calf neuromuscular function during BR, although sample size issues may have played a role. The exercise regimen maintained thigh size and MVC strength, but promoted a loss in contractile speed. Whereas contractile speed improved for the calf, the exercise regimen only partially preserved calf size and MVC strength. Modification of the exercise regimen seems warranted.

Albuterol aids resistance exercise in reducing unloading-induced ankle extensor strength losses

While resistance exercise (REX) reduces ankle extensor (AE) mass and strength deficits during short-term unloading; additional treatments, concurrently administered with REX, are required to attenuate the greater losses seen with longer unloading periods. Subjects performed left leg REX, which otherwise refrained from ambulatory and weight-bearing activity for 40 days, while randomized to a capsule (placebo, albuterol) dosing regimen with no crossover to note whether albuterol helps REX mitigate unloading-induced AE losses. A third group of subjects served as unloaded controls. On days 0, 20, and 40, the following data were collected from the left leg: calf cross-sectional area and AE strength measures. Cross-sectional area was estimated using anthropometric methodology, whereas AE strength data were obtained from eight unilateral calf-press repetitions on an inertial-based REX device. Repeated-measures mixed-factorial 3 x 3 analyses of covariance, with day 0 values as a covariate, revealed group x time interactions for the strength variables eccentric total work (ETW) and average power (EAP). Tukey's honestly significant difference shows REX-placebo subjects incurred significant ETW and EAP losses by day 40, whereas the REX-albuterol treatment evoked strength gains to those same variables without concurrent muscle accretion. Corresponding concentric variables did not display similar changes. Day 40 control data significantly declined for many variables; relative to the REX-albuterol treatment, some losses were significant after 20 days. ETW and EAP gains to unloaded AE may be due to one or more mechanisms. Continued research identifying mechanisms responsible for such changes, as well as the safety of REX-albuterol administration in other models, is warranted.

Abnormal mitochondrial function and muscle wasting, but normal contractile efficiency, in haemodialysed patients studied non-invasively in vivo.

Muscle dysfunction, which contributes to morbidity in patients on haemodialysis, has several manifestations and a number of possible causes. We applied the non-invasive techniques of (31)P-magnetic resonance spectroscopy ((31)P-MRS), magnetic resonance imaging (MRI) and near-infrared spectroscopy (NIRS) to calf muscle of dialysed patients to define the abnormalities in muscle cross-sectional area (CSA), contractile efficiency, mitochondrial function and vascular O(2) supply. We performed (31)P-MRS/NIRS/MRI studies on the lateral gastrocnemius during isometric plantarflexion and recovery in 23 male patients on haemodialysis (age 24-71 years; haemoglobin 9.9-14.2 g/dl; bicarbonate 17-30 mmol/l; urea reduction ratio 53-77%; parathyroid hormone 1-95 U/l) and 15 male controls (age 29-71 years). To understand the relationships between calf CSA and body mass we also performed MRI only in a further six male patients and 18 male controls. In patients, exercise duration was 30+/-11% lower than in controls. Muscle CSA was lower by 26+/-5%, but contractile efficiency (force/CSA/ATP turnover) was normal. Slowing of post-exercise phosphocreatine (PCr) recovery implied a 22+/-5% defect in effective 'mitochondrial capacity'. That PCr recovery was slow relative to NIRS recovery suggests that this is largely an intrinsic mitochondrial problem (not the result of impaired O(2) supply), one which, furthermore, correlated with CSA. Urea reduction ratio showed a negative correlation with body mass and CSA, but none with PCr rate constant. The relationships to urea reduction ratio reflect the effect of muscle mass on dialysis efficiency, rather than direct effects on muscle CSA or metabolism. The relationship between PCr recovery and calf CSA suggests a role for the mitochondrial defect, whatever its cause, in the development of muscle wasting, although a common cause (e.g. physical inactivity) for both abnormalities cannot be ruled out.

Water exchange induced by unilateral exercise in active and inactive skeletal muscles.

Water exchange was evaluated in active (E-leg) and inactive skeletal muscles by using (1)H-magnetic resonance imaging. Six healthy subjects performed one-legged plantar flexion exercise at low and high workloads. Magnetic resonance imaging measured calf cross-sectional area (CSA), transverse relaxation time (T2), and apparent diffusion capacity (ADC) at rest and during recovery. After high workload, inactive muscle decreased CSA and T2 by 2.1% (P < 0.05) and 3.1% (P < 0.05), respectively, and left ADC unchanged. E-leg simultaneously increased CSA, T2, and ADC by 4.2% (P < 0.001), 15.5% (P < 0.05), and 12.5% (P < 0.001), respectively. In conclusion, ADC and T2 correlated highly with muscle volume, indicative of extravascular water displacement closely related to muscle activity and perfusion, which was presumably a combined effect of increased intracellular osmoles and hydrostatic forces as driving forces. A distinguishable muscle temperature release was initially detected in the E-leg after high workload, and the ensuing recovery of ADC and T2 indicated delayed interstitial restitution than restitution of the intracellular compartment. Furthermore, absorption of extravascular water was detected in inactive muscles at contralateral high-intensity exercise.

Effects of whole-body and local thermal stress on hydrostatic volume changes in the human calf.

In the present study, we examined the effect of thermal stress on the magnitude and pattern of change in leg volume during orthostatic stress and thigh occlusion in humans. Ten healthy volunteers underwent whole-body thermal stress produced by a cool- or hot-water-perfused suit and local heat stress of the calf. During whole-body thermal stress, changes of calf circumference during head-up tilt (HUT) at angles of 15 degrees and 60 degrees for 2 min each were monitored. In the supine position, the distensibility of the calf veins was evaluated from the magnitude and half-time of the change in calf circumference during thigh cuff occlusions at 20, 30, 50, 70, and 80 mmHg. Skin blood flow in the calf was measured by laser-Doppler flowmetry. Skin blood flow increased by [mean (SEM)] 295 (71)% with whole-body heating and decreased by 31 (4)% with whole-body cooling. Local heating of the calf increased skin blood flow in the heated area by 263 (25)%. During HUT, the calf cross-sectional area, calculated from the circumference, increased rapidly during whole-body heating and slowly during the cooling. The magnitude of the increase in calf area with HUT did not alter during whole-body heating, whereas it was reduced during cooling compared with the normothermic control. Whole-body and local heating did not alter the magnitude of change in calf area at a given cuff pressure, whereas whole-body cooling decreased it. The time to the half-maximal response of the change in calf circumference was shortened by 35 (17)% during whole-body heating and by 44 (4)% during local heating, whereas it was prolonged by 31 (16)% during whole-body cooling compared with the normothermic control. These results indicate that the magnitude and the pattern of change in calf volume during the early phase of orthostatic stress are modulated due to the changes in venous distensibility and blood flow in the skin during thermal loading.

MUSCLE POWER AND CYCLING SPEED IN 5-7 YEAR OLD CHILDREN BORN AT VERY LOW BIRTHWEIGHT (500-1500 GRAMS) 21

Recent years have seen an increase in the survival of children with a very low birthweight (VLBW < 1.500 g). Such children seem to be shorter and lighter than their full-term peers, but there is no information regarding their muscle performance. This study is intended to determine whether VLBW is accompanied by a deficiency in muscle power and maximal cycling speed at age 5-7 years. Nine VLBW children (6.5±0.6 y, birthweight 1.032±296 g) were compared with age-matched normal birthweight (NBW) controls(6.2±0.8 y, birthweight 3535±912g). The VLBW group had no overt neuromuscular deficiency. Peak (PP) and mean (MP) muscle power were determined by the Wingate Test and maximal speed during 30-s cycling at“Zero” resistance. As seen in the Table, the VLBW children were lighter, shorter and leaner (bioimpedance and SF analysis). They also had a smaller lean thigh and calf cross-sectional area (X-sec area, calculated from circumferences and skinfolds - SF). However, there were no inter-group differences in PP and MP, whether calculated in absolute power units, per kg body mass, fat free mass (FFM) or X-sec area. Nor was there a difference in maximal pedalling speed. In conclusion, by age 5-7 years, VLBW does not seem to induce a deficiency in muscle power or maximal cycling speed.

Chronic changes in skeletal muscle histology and function in peripheral arterial disease.

Peripheral arterial disease (PAD) is associated with an impairment in exercise performance and muscle function that is not fully explained by the reduced leg blood flow during exercise. This study characterized the effects of PAD on muscle function, histology, and metabolism. Twenty-six patients with PAD and six age-matched control subjects were studied. Ten of the PAD patients had unilateral disease, which permitted paired comparisons between their diseased and nonsymptomatic legs. All PAD patients had a lower peak treadmill walking time and peak oxygen consumption than controls. Vascular disease (diseased leg in unilateral patients and the most severely diseased leg in bilateral patients) was associated with decreased calf muscle strength compared with control values. In patients with unilateral disease, the diseased legs had a greater percentage of angular fibers (indicating chronic denervation) and a decreased type II fiber cross-sectional area (expressed as percent of total fiber area) compared with the nonsymptomatic, or control, legs. In diseased legs, gastrocnemius muscle strength was correlated with the total calf cross-sectional area (r = 0.78, p < 0.05) and type II fiber cross-sectional area (r = 0.63, p < 0.05). Activities of citrate synthase, phosphofructokinase, and lactate dehydrogenase in all 26 PAD patients (most diseased leg) did not differ from control values. Despite a wide range in citrate synthase activity in PAD patients, activity of this enzyme was not correlated with muscle strength or treadmill exercise performance. In patients with PAD, gastrocnemius muscle weakness is associated with muscle fiber denervation and a decreased type II fiber cross-sectional area. In contrast, the PAD patients displayed substantial heterogeneity in muscle enzyme activities that was not associated with exercise performance. Denervation and type II fiber atrophy may contribute to the muscle dysfunction in patients with PAD and further confirm that the pathophysiology of chronic PAD extends beyond arterial obstruction.

The effects of short-term voluntary immobilization on the contractile properties of the human triceps surae.

In four male subjects one leg was immobilized in a full leg cast for 2 weeks. Measurements of the contractile properties of both triceps surae were made before, during and after immobilization. There was a significant increase in the mean twitch time to peak tension (Tc) after 1 week of immobilization from 126 +/- 10 ms to 143 +/- 20 ms (P less than 0.05) and in the half-relaxation time (T1/2r) from 88 +/- 7 ms to 107 +/- 12 ms (P less than 0.01). There were no further significant (P less than 0.1) changes in the twitch characteristics during the second week of immobilization. The strength of a maximal voluntary contraction (m.v.c.) declined by 11% (P less than 0.05) after 1 week and 24% (P less than 0.05) after 2 weeks. Twitch tension, tetanic tension and muscle fatigability were not significantly altered during immobilization. Muscle (plus bone) calf cross-sectional area (A) was reduced by 5% (P less than 0.01) after 1 week and a further 3% (P less than 0.05) after 2 weeks. The Tc and T1/2r of the twitch, m.v.c. and A returned to control values within 2, 7, 4 and 14 d respectively. No significant (P less than 0.01) changes were observed in the mechanical properties of the triceps surae of the contralateral limb during the period of immobilization. The results suggest that short-term voluntary immobilization is associated with atrophy and a diminished capacity of the muscle to develop maximal voluntary force.(ABSTRACT TRUNCATED AT 250 WORDS)