Measurement of maximal muscle cross-sectional area of the elbow extensors and flexors in children,teenagers and adults

Abstract

The aims of this study were to examine age and sex differences in elbow extensor and flexor anatomical muscle cross-sectional area (mCSA) measured by magnetic resonance imaging (MRI) and the location of maximal mCSA as a percentage of the distance from the distal to the proximal end of the humerus. Ninety-five individuals spread across the age groups 9 – 10 years, 16 – 17 years and 21 years participated in the study. Muscle cross-sectional area derived from the manual MRI tracing proved to be highly reliable in terms of limits of agreement (?2.5 to 1.5 cm²) and the intraclass correlation coefficient (ICC = 0.998). A sex-by-age group analysis of variance revealed significant effects (P < 0.01) of sex, group and a sex-by-group interaction, the latter reflecting a greater increase in males than females of upper arm mCSA from childhood to adulthood. Extensor mCSA was more proximal (55 ± 6%) than that of the flexors (28 ± 6%). A significant effect (P < 0.01) of group was found for location of maximal extensor mCSA, reflecting its more distal position with increasing age. Measurements of muscle size should be made at the individually determined position of maximal mCSA if interpreting data collected during growth and maturation, especially if the muscle group of interest is the elbow extensors and if different age groups are being monitored.     

Angle-specific impairment of elbow flexors strength after isometric exercise at long muscle length

In this study, we examined the long-term reductions in maximal isometric force (MIF) caused by a protocol of repeated maximal isometric contractions at long muscle length. Furthermore, we wished to ascertain whether the reductions in MIF are dependent on muscle length--that is, are the reductions in MIF more pronounced when the muscle contracts at a short length. The MIF of the elbow flexors of seven young male volunteers was measured at five different elbow angles between 50 degrees and 160 degrees. On a separate day, the participants performed 50 maximal voluntary isometric muscle contractions with the elbow flexors at a lengthened position; that is, with the shoulder hyperextended at 45 degrees and the elbow joint fixed at 140 degrees. Following this exercise, the MIF at the five elbow angles, range of motion, muscle soreness and plasma creatine kinase activity were measured at 24 h intervals for 4 days. On day 1, the decline in MIF was higher at the more acute elbow angles of 50 degrees (42 +/- 8%) and 70 degrees (39 +/- 8%; both P<0.01) than at 90 degrees (26 +/- 4%) and 140 degrees (16 +/- 3%; both P<0.01). No significant reduction in MIF was evident at an elbow angle of 160 degrees. Maximal isometric force at an elbow angle of 140 degrees was fully restored on day 3, whereas at an angle of 50 degrees it remained depressed for the 4 day observation period. Restoration of MIF was a function of the elbow angle, with force recovery being less at the smaller angles. The range of motion was decreased by 14 +/- 2 degrees on day 1 (P<0.01) and did not return to baseline values by day 4. Muscle soreness ratings remained significantly elevated for the 4 day period. Serum creatine kinase peaked on day 1 (522 +/- 129 IU, P<0.01) and decreased thereafter. We conclude that the disproportionate decrease in MIF at the small elbow angles and the length-specific recovery in MIF after repeated maximal isometric contractions at long muscle length may be explained by the presence of overstretched sarcomeres that increased in series compliance of the muscle, therefore causing a rightward shift of the force-length relationship.     

The validity of estimating triceps brachii volume from single MRI cross-sectional area before and after resistance training

The aim of this study was to determine whether triceps brachii muscle volume can be adequately estimated from a single anatomical cross-sectional area (ACSA) and can the same model be used for prediction after training. Thirty-five healthy male non-athletes (age 21.6 ± 2.5 years, body mass index 24.8 ± 3.5 kg · m(-2)) volunteered for this study. The volumes of the upper arm extensors were calculated from magnetic resonance imaging (MRI) sequence scans and regression models were developed, which were used to predict muscle volumes from single MRI cross-sectional scans taken at different points along the humerus length. The same procedure was repeated after 12 weeks of maximal resistance training of the elbow extensors. Correlation coefficients were calculated for Model A with CSA(max), humerus length (HL), and body mass index (r = 0.919), a model with CSA(50%) and HL (r = 0.922), and a model with CSA(60%) and HL (r = 0.920) (P < 0.001). The standard error of estimate for Model A, Model CSA(50%), and Model CSA(60%) was 8.0%, 7.7%, and 7.8% respectively. Thesame prediction formula can be used for the left arm (r = 0.904). If a single ACSA is used for triceps brachii volume prediction, the best fit is with Model CSA(60%) and HL, both before and after training (r = 0.941). By introducing humerus length into the calculation, we simplify the procedure for volume measurement, since it can be obtained during MRI scanning.     

Effects of cold water immersion on the symptoms of exercise-induced muscle damage.

Cryotherapy is an effective treatment for acute sports injury to soft tissue, although the effect of cryotherapy on exercise-induced muscle damage is unclear. The aim of this study was to assess the effects of cold water immersion on the symptoms of exercise-induced muscle damage following strenuous eccentric exercise. After performing a bout of damage-inducing eccentric exercise (eight sets of five maximal reciprocal contractions at 0.58 rad x s(-1)) of the elbow flexors on an isokinetic dynamometer, 15 females aged 22.0+/-2.0 years (mean +/- s) were allocated to a control group (no treatment, n = 7) or a cryotherapy group (n = 8). Subjects in the cryotherapy group immersed their exercised arm in cold water (15 degrees C) for 15 min immediately after eccentric exercise and then every 12 h for 15 min for a total of seven sessions. Muscle tenderness, plasma creatine kinase activity, relaxed elbow angle, isometric strength and swelling (upper arm circumference) were measured immediately before and for 3 days after eccentric exercise. Analysis of variance revealed significant (P < 0.05) main effects for time for all variables, with increases in muscle tenderness, creatine kinase activity and upper arm circumference, and decreases in isometric strength and relaxed elbow angle. There were significant interactions (P<0.05) of group x time for relaxed elbow angle and creatine kinase activity. Relaxed elbow angle was greater and creatine kinase activity lower for the cryotherapy group than the controls on days 2 and 3 following the eccentric exercise. We conclude that although cold water immersion may reduce muscle stiffness and the amount of post-exercise damage after strenuous eccentric activity, there appears to be no effect on the perception of tenderness and strength loss, which is characteristic after this form of activity.     

Inspiratory muscle fatigue in swimmers after a single 200 m swim

Inspiratory muscle fatigue may occur in as little as 6 min during high-intensity spontaneously breathing exercise. The aims of this study were to determine whether inspiratory muscle fatigue occurs during swimming exercise and whether inspiratory muscle strength differs between the supine and standing body positions. Seven competitive swimmers were recruited to perform a single 200 m front-crawl swim, corresponding to 90-95% of race pace. Inspiratory muscle strength was measured at residual volume using a hand-held mouth pressure meter that measured maximal inspiratory pressure in the upright and supine positions. At baseline, maximal inspiratory pressure in the supine position was significantly lower than maximal inspiratory pressure in the upright position (112 +/- 20.4 and 133 +/- 16.7 cmH2O, respectively; P < or = 0.01). Post-exercise maximal inspiratory pressure in the supine position (80 +/- 15.7 cmH2O) was significantly lower than baseline maximal inspiratory pressure in the supine position (P < or = 0.01). The results indicate that a single 200 m front-crawl swim corresponding to 90-95% of race pace was sufficient to induce inspiratory muscle fatigue in less than 2.7 min. Furthermore, although diaphragm muscle length is optimized when supine, our results indicate that the force output of the diaphragm and inspiratory accessory muscles is greater when upright than when supine.     

Relationships between muscle fibre characteristics and physical performance capacity in trained athletic boys

The relationships between muscle fibre characteristics and the physical performance capacity of trained athletic boys (aged 11-13 years) were studied over 2 days. The subjects were divided into two groups according to muscle fibre distribution. The 'fast' group (FG) comprised 10 subjects (sprinters, weightlifters, tennis players) with more than 50% fast-twitch fibres (type II), and the 'slow' group (SG) comprised 8 subjects (endurance runners, tennis players, one weightlifter) with more than 50% slow-twitch fibres (type I) in their vastus lateralis muscle. The 'fast' group had 59.2 +/- 6.3% and the 'slow' group had 39.4 +/- 9.8% type II fibres. Other clear differences (P less than 0.05-0.01) between the groups were observed as regards reaction time, rate of force development and rise of the body's centre of gravity in the squatting jump. For these variables, the 'fast' group was superior to the 'slow' group. Muscle fibre distribution (% type II) correlated (P less than 0.05-0.01) negatively with reaction time. Muscle fibre area (% type II) correlated negatively with reaction time (P less than 0.05-0.001) and positively with chronological age (P less than 0.05) height (P less than 0.05), mass (P less than 0.001), serum testosterone (P less than 0.05), force production (P less than 0.05-0.01) and blood lactate (P less than 0.05) in the 60-s maximal anaerobic test. There were no significant correlations between muscle fibre characteristics and maximal oxygen uptake. The present study assumes that heredity partly affects the selection of sporting event. Growth, development and training are associated with muscle fibre area, which affects the physical performance capacity of the neuromuscular system in trained young boys.     

Pre-season physiological characteristics of English first and second division soccer players.

This investigation was undertaken in an effort to establish physiological characteristics of soccer players and to relate them to positional roles. A total of 135 footballers (age 24.4 +/- 4.6 years) were assessed for body mass, % body fat, haemoglobin, maximal oxygen uptake (VO2 max), leg power, anaerobic capacity and speed prior to an English league season. The sample included 13 goalkeepers, 22 full-backs, 24 centre-backs, 35 midfield players and 41 forwards. The goalkeepers were significantly heavier (86.1 +/- 5.5 kg; P < 0.01) than all groups except the centre-backs, had significantly higher estimated body fat percentages than centre-backs, forwards, midfield players (P < 0.01) or full-backs (P < 0.05), significantly lower estimated VO2 max values (56.4 +/- 3.9 ml kg-1 min-1; P < 0.01) and were slowest over 60 m (12.71 +/- 0.42 s). The midfield players had the highest predicted VO2 max values (61.4 +/- 3.4 ml kg-1 min-1), this being significantly greater (P < 0.05) than for the centre-backs. The forwards were the fastest group over 60 m (12.19 +/- 0.30 s), being significantly quicker than goalkeepers or centre-backs (P < 0.01) and full-backs (P < 0.05). Anaerobic power, as well as knee extensor torques (corrected for body mass) and extensor-flexor ratios, were similar between groups. No difference in estimated body fat percentage was observed between any of the outfield players, and haemoglobin concentrations were similar among players of all positions.(ABSTRACT TRUNCATED AT 250 WORDS)     

我国优秀划艇运动员肩、肘关节肌力特征的比较研究

运用等速测试系统对备战伦敦奥运会的国家划艇运动员的肩关节、肘关节肌力进行测试与分析。结果表明:1)从力矩角度来看,优秀运动员与一般运动员在肩、肘关节肌力特征中存在显著性差异(P<0.05),且屈肌和伸肌的力矩角度分别呈现不同的特征;2)从峰力矩比值来看,在不同速度运动下,国家队优秀运动员和一般运动员均存在屈伸比的失衡问题,即最大力量上存在屈伸肌群发展的不合理化现象(<50%),随着测试速度的增加,屈伸比呈递减趋势;3)在肘关节两侧同名肌群的比较中同样存在不均衡现象,尤其是伸肌的两侧差值较大;4)肩关节的肌力特征也存在类似的现象,但屈肌明显不如伸肌力量。结论:应逐步加强划艇运动员肩、肘关节同侧屈伸肌群和异侧同名肌群的力量均衡性训练,并提高肩关节的屈肌力量能力。     

Effects of dynamic resistance training on fascicle length and isometric strength

The aims of this study were to assess changes in muscle architecture, isometric and dynamic strength of the leg extensor muscles, resulting from dynamic resistance training, and the relationships between strength and muscle architecture variables. The participants (n = 30) were randomly assigned to one of two groups. The training group (n = 16; age 21.8 +/- 2.3 years, body mass 74.8 +/- 9.2 kg, height 1.75 +/- 0.08 m) performed dynamic resistance training for 13 weeks. The control group (n = 14; age 19.9 +/- 1.5 years, body mass 74.0 +/- 8.5 kg, height 1.76 +/- 0.05 m) did not perform any resistance training. Maximal dynamic and isometric strength were tested in both groups, before and after the training period. The members of the training group used the free-weight squat lift (90 degrees ) as their training exercise. The concentric phase of the squat was performed explosively. Skeletal muscle architecture of the vastus lateralis was visualized using ultrasonography. At the end of the study, significant increases in vastus lateralis muscle thickness (+6.9%, P < 0.001), fascicle length (+10.3%, P < 0.05), one-repetition maximum (+8.2%, P < 0.05), rate of force development (+23.8%, P < 0.05) and average force produced in the first 500 ms (+11.7%, P < 0.05) were seen only in the training group. Adaptations to the muscle architecture in the training group limited the loss of fibre force, and improved the capacity for developing higher velocities of contraction. The architectural changes in the training group were similar to those seen in studies where high-speed training was performed. In conclusion, dynamic resistance training with light loads leads to increases in muscle thickness and fascicle length, which might be related to a more efficient transmission of fibre force to the tendon.     

Effects of inspiratory muscle training on time-trial performance in trained cyclists

We evaluated the effects of specific inspiratory muscle training on simulated time-trial performance in trained cyclists. Using a double-blind, placebo-controlled design, 16 male cyclists (VO2max = 64 +/- 2 ml x kg(-1) x min(-1); mean +/- s(x)) were assigned at random to either an experimental (pressure-threshold inspiratory muscle training) or sham-training control (placebo) group. Pulmonary function, maximum dynamic inspiratory muscle function and the physiological and perceptual responses to maximal incremental cycling were assessed. Simulated time-trial performance (20 and 40 km) was quantified as the time to complete pre-set amounts of work. Pulmonary function was unchanged after the intervention, but dynamic inspiratory muscle function improved in the inspiratory muscle training group (P < or = 0.05). After the intervention, the inspiratory muscle training group experienced a reduction in the perception of respiratory and peripheral effort (Borg CR10: 16 +/- 4% and 18 +/- 4% respectively; compared with placebo, P < or = 0.01) and completed the simulated 20 and 40 km time-trials faster than the placebo group [66 +/- 30 and 115 +/- 38 s (3.8 +/- 1.7% and 4.6 +/- 1.9%) faster respectively; P = 0.025 and 0.009]. These results support evidence that specific inspiratory muscle training attenuates the perceptual response to maximal incremental exercise. Furthermore, they provide evidence of performance enhancements in competitive cyclists after inspiratory muscle training.     

Oxygen uptake kinetics in children and adults after the onset of moderate-intensity exercise

The literature suggests that the oxygen uptake (VO2) response to the onset of moderate-intensity exercise may be both mature from childhood and independent of sex. Yet the cardiorespiratory response to exercise and the metabolic profile of the muscle appear to change with growth and development and to differ between the sexes. The aim of this study was to investigate further changes in the VO2 kinetic response with age and sex. Participants completed a series of no less than four step change transitions, from unloaded pedalling to a constant work rate corresponding to 80% of their previously determined ventilatory threshold. Each participant's breath-by-breath responses were interpolated to 1 s intervals, time aligned and then averaged. A single exponential model that included a time delay was used to analyse the averaged response following phase 1 (15 s). Participants with parameter confidence intervals more than +/- 5 s were removed from the sample; the results for the remaining 13 men and 12 women (age 19-26 years), 12 boys and 11 girls (age 11-12 years) were used for statistical analysis. Children had a significantly shorter time constant than adults, both for males (19.0+/-2.0 and 27.9+/-8.6 s respectively; P<0.01) and females (21.0+/-5.5 and 26.0+/-4.5 s respectively; P<0.05). There were no significant differences in the time constant between the sexes for either adults or children (P>0.05). A significant relationship between the time constant and peak VO2 was found only in adult males (P<0.05). A shorter time constant in children may reflect an enhanced potential for oxidative metabolism.     

Size–strength relationships of the elbow flexors and extensors are not affected by age or gender

Abstract

In the present study, we examined the relationships between muscle volume and joint torque for the elbow flexors and extensors in young and elderly individuals, with the aim of evaluating age effects on these relationships. The participants were 45 young (27 men and 18 women aged 20–37 years) and 51 elderly (19 men and 32 women aged 60–77 years) individuals. The joint torques developed during isometric maximal voluntary elbow flexion and extension were measured using a torque meter. The muscle volumes of the elbow flexors and extensors were determined by magnetic resonance imaging. For the elbow flexors, joint torque was significantly correlated with muscle volume in both young and elderly individuals (r=0.564–0.872). There were also significant correlations between muscle volume and joint torque for the elbow extensors in elderly men and women as well as in young men and women (r=0.715–0.826). None of the y-intercepts of the regression lines between muscle volume and joint torque were significantly different from zero. Furthermore, no significant age or gender effects on the joint torque per muscle volume of the elbow flexors and extensors were observed. The present results suggest that muscle volume is a main determinant of joint torque regardless of age and gender, for both muscle groups.     

Angle-specific impairment of elbow flexors strength after isometric exercise at long muscle length

Abstract

In this study, we examined the long-term reductions in maximal isometric force (MIF) caused by a protocol of repeated maximal isometric contractions at long muscle length. Furthermore, we wished to ascertain whether the reductions in MIF are dependent on muscle length — that is, are the reductions in MIF more pronounced when the muscle contracts at a short length. The MIF of the elbow flexors of seven young male volunteers was measured at five different elbow angles between 50° and 160°. On a separate day, the participants performed 50 maximal voluntary isometric muscle contractions with the elbow flexors at a lengthened positions that is, with the shoulder hyperextended at 45° and the elbow joint fixed at 140°. Following this exercise, the MIF at the five elbow angles, range of motion, muscle soreness and plasma creatine kinase activity were measured at 24 h intervals for 4 days. On day 1, the decline in MIF was higher at the more acute elbow angles of 50° (42±8%) and 70° (39±8%; both P<0.01) than at 90° (26±4%) and 140° (16±3%; both P<0.01). No significant reduction in MIF was evident at an elbow angle of 160°. Maximal isometric force at an elbow angle of 140° was fully restored on day 3, whereas at an angle of 50° it remained depressed for the 4 day observation period. Restoration of MIF was a function of the elbow angle, with force recovery being less at the smaller angles. The range of motion was decreased by 14±2° on day 1 (P<0.01) and did not return to baseline values by day 4. Muscle soreness ratings remained significantly elevated for the 4 day period. Serum creatine kinase peaked on day 1 (522±129 IU, P<0.01) and decreased thereafter. We conclude that the disproportionate decrease in MIF at the small elbow angles and the length-specific recovery in MIF after repeated maximal isometric contractions at long muscle length may be explained by the presence of overstretched sarcomeres that increased in series compliance of the muscle, therefore causing a rightward shift of the force-length relationship.     

Bone mass,bone mineral density and muscle mass in professional golfers

The aim of this study was to determine the effects of long-term professional golf participation on whole-body and regional bone mass and density. Dual-energy X-ray absorptiometry was performed on 15 male professional golfers and 18 sedentary individuals, matched for sex, race, age (29+/-1 and 25+/-1 years, respectively), body mass (79+/-2 and 74+/-2 kg), height (1.78+/-0.01 and 1.77+/-0.02 m) and percent body fat (20+/-2 and 21+/-2%; mean +/- sx). We found that long-term professional golf participation is not associated with significant increments in regional or whole-body bone mass or density. Neither the lumbar spine nor the femoral neck showed any noticeable enhancement of bone mass in professional golfers compared with controls from the same population. The only effect of professional golf participation on regional body composition was a 9% increase in muscle mass in the dominant arm (P < 0.05).     

Age at menarche in competitive figure skaters: variation by competency and discipline.

We estimated age at menarche in a cross-sectional sample of 159 competitive figure skaters aged 11-22 years. The sample represented three standards (test stream, pre-elite, elite) and three disciplines (free skaters, pair skaters, dancers). The status quo (yes/no) and retrospective methods were used. Estimated age at menarche based on probit analysis of the status quo data was 14.2 +/- 0.5 years, with 95% confidence intervals of 13.2 to 15.2 years. Mean recalled age at menarche for 67 skaters aged 16 years or over was 13.6 +/- 1.2 years. Comparisons of skaters by standard and discipline were limited to skaters > or = 16 years. Menarche was, on average, significantly later (P < 0.01) in elite (n = 36; 14.0 +/- 1.4 years) than in test stream (n = 15; 12.9 +/- 0.8 years) skaters. Age at menarche in pre-elite skaters (n = 16; 13.5 +/- 0.9 years) did not differ significantly from the other two groups. By discipline, menarche was, on average, significantly later (P < 0.01) in pair skaters (n = 12; 14.5 +/- 1.3 years) than in both free skaters (n = 38; 13.4 +/- 1.0 years) and dancers (n = 17; 13.4 +/- 1.4 years). Early maturing girls (menarche < 12.0 years; n = 2) were not represented in this sample of competitive figure skaters. Mean recalled age at menarche of mothers of skaters (n = 84) was 13.7 +/- 1.3 years and the mother-daughter correlation (n = 56 pairs) was 0.45 (P < 0.01). Later maturation was thus characteristic of competitive figure skaters, particularly in elite and more specialized pair skaters, and there was a significant familial resemblance.     

The relationship between torque and joint angle during knee extension in boys and men.

The length-tension relationship of muscle contraction is well documented in adults. However, research on this relationship in children has been limited. The aim of this study was to compare differences in the torque-joint angle relationship of the quadriceps muscle in children and adults. Eight boys aged 8-10 years and eight men aged 20-26 years performed two maximal voluntary isometric contractions at six knee joint angles (20 degrees, 40 degrees, 60 degrees, 80 degrees, 90 degrees, 100 degrees). The mean of the two trials was used as the performance measure. Both groups demonstrated an expected increase in relative torque as the joint angle increased (P< 0.05). The men produced significantly greater relative torque at 20 degrees, 40 degrees and 60 degrees knee flexion (P < 0.05). The percentage of maximal torque at these angles for the men and boys respectively were: 35.2+/-4.3 vs 15.2+/-12%, 63.6+/-9.1 vs 51.8+/-16.8% and 93.6+/-6.5 vs 84.4+/-14.4%. There were no group differences at 80 degrees or 90 degrees. Peak torque was attained at 80 degrees in men, but decreased significantly (P< 0.05) at 90 degrees and 100 degrees. For boys, peak torque was attained at joint angles of 80 degrees and 90 degrees. The reduction in peak torque at 100 degrees was not statistically significant, but the relative torque at this angle was lower in men than in boys (77.9+/-13.7 vs 87.1+/-10.4%; P< 0.05). In conclusion, the relationship between torque and joint angle appears to be affected by age.     

Somatotype and size of elite female basketball players

The aim of this study was to compare the somatotype and size of elite female basketball players in terms of playing position and team performance. Anthropometry and somatotype data were collected on 168 players from 14 countries before the Women's World Basketball Championship, Australia, 1994. There were 64 guards (mean +/- s: age 25.4 +/- 3.3 years, height 1.72 +/- 0.06 m, mass 66.1 +/- 6.2 kg, somatotype = 2.9-3.9-2.6), 57 forwards (age 25.2 +/- 3.8 years, height 1.81 +/- 0.06 m, mass 73.3 +/- 5.9 kg, somatotype = 2.8-3.5-3.2) and 47 centres (age 24.1 +/- 3.1 years, height 1.90 +/- 0.06 m, mass 82.6 +/- 8.2 kg, somatotype = 3.2-3.1-3.4). Mean somatotypes by position were significantly different (F = 7.73, P < 0.01). Guards had greater mesomorphy than centres and less ectomorphy than forwards and centres. When discriminant function analysis was applied to endomorphy, mesomorphy, ectomorphy, age, height and mass, only height, mass and ectomorphy entered (Wilks' lambda = 0.351, F = 31.40, P < 0.000), 70% of the variance was accounted for, and 72% of players were correctly classified. In the four top versus four bottom teams, guards were taller and more ectomorphic, forwards were taller, with lower mesomorphy and higher ectomorphy, and centres did not differ. Thus there are some differences in somatotypes by position and team placing, but the combination of height, mass and ectomorphy provide the best differentiation by position.     

Estimation of thigh muscle and adipose tissue volume using magnetic resonance imaging and anthropometry

Thigh muscle volume is a useful determinant of functional fitness. However, anthropometric prediction of muscle content is influenced by the variability of adipose tissue accumulation. The aims of this study were to predict thigh muscle and adipose tissue volumes from anthropometry and to assess the validity of the method by examining the various components of the measurements and the assumptions involved. The 19 participants (9 men, 10 women; age 23-49 years) varied in adiposity. They all underwent magnetic resonance imaging (MRI) of the upper leg and the eight men and two women with the lowest adiposity underwent detailed anthropometry involving girths and skinfolds. Using MRI as the reference method, muscle volume was predictedfrom anthropometry using a circular concentric model, and the assumptions inherent in the method were tested further using the MRI data alone. Muscle volume was best predicted by anthropometry in the 10 leanest participants using a five-slice truncated cone model that overestimated the mean MRI value by 30% (R2 = 0.95; standard error of estimate = 288 cm3; P < 0.001). A single skinfold plus girth measurement at the mid-thigh almost matched its predictive ability, but with an increased bias. Measurements of leg circumference by means of the two techniques agreed well. The assumption of a circular cross-section was valid. In contrast, the agreement between skinfold thickness measured by caliper and superficial adipose tissue thickness by MRI was poor, contributing to the scatter of fat and lean area comparisons. An anterior skinfold thickness measurement underestimated the area of superficial adipose tissue at that level, particularly at the most proximal and distal sites. Although these limitations increase the uncertainties of muscle volume determination by anthropometry, they do not prevent its valid prediction in leaner individuals. The prediction of superficial adipose tissue was poorer.     

Effects of sensory-level high-volt pulsed electrical current ondelayed-onset muscle soreness

Ten healthy males and ten healthy females aged 21.5 +/- 3.2 years (mean +/- s) participated in the study, which was designed to evaluate the effectiveness of sensory level-high volt pulsed electrical current (HVPC) on delayed-onset muscle soreness (DOMS). Arm discomfort, elbow extension range of motion and isometric elbow flexion strength were obtained as baseline measurements. Delayed-onset muscle soreness was induced in the participants' dominant or non-dominant arm using two sets of 20 maximal eccentric elbow flexion contractions. After the induction of DOMS, the participants were randomly divided into an experimental condition (HVPC) or a placebo condition. The experimental condition consisted of 20 min of HVPC immediately after the induction of DOMS, and 20 min every 24 h for three consecutive days thereafter. The participants in the placebo condition received an intervention similar in design; however, no electrical current was administered. Baseline measurements were reevaluated at 24, 48, 72 and 96 h after the induction of DOMS. Three weeks later, the participants returned and the protocol was repeated on the contralateral limb, using the opposite intervention (HVPC or placebo). Repeated-measures analysis of variance revealed a significant increase in overall arm discomfort, decrease in elbow extension and decrease in isometric strength for both conditions over time. No significant main effect of treatment, or time-by-treatment interaction, was found for the HVPC condition when compared with the placebo condition for any variable. Sensory-level HVPC, as utilized in our application, was ineffective in reducing the measured variables associated with DOMS.     

The isolated and combined effects of selected physical activity and ibuprofen on delayed-onset muscle soreness

Delayed-onset muscle soreness refers to the skeletal muscle pain that is experienced following eccentric exercise. The aim of the present study was to examine the physiological effects of physical activity with or without ibuprofen on delayed onset muscle soreness. Forty-four non-athletic male volunteers (age 24.3 +/- 2.4 years) were randomly assigned to one of four groups: physical activity (n = 11), ibuprofen (n = 11), physical activity and ibuprofen (combination, n = 11), or control (n = 11). The physical activity programme comprised 5 min of walking and jogging, 10 min of static stretching of the hands and shoulder girdle, and 5 min of concentric movements with sub-maximal contractions. The total amount of ibuprofen consumed by a single individual was 2800 mg; this was taken from 1 h before the eccentric actions up to 48 h after it. Delayed onset muscle soreness was induced by performing 70 eccentric contractions of the biceps muscle of the non-dominant side on a modified arm curl machine. Perceived muscle soreness, maximal eccentric contraction, creatine kinase enzyme activity and elbow range of motion were assessed 1 h before and 1, 24 and 48 h after the eccentric actions. The results indicated that, after the eccentric actions, soreness increased (P < 0.001) across time in all groups, with the highest values being recorded at 24 h. At 24 and 48 h, greater soreness (P < 0.001) was observed in the control group than in the physical activity and combination groups. After the eccentric actions, creatine kinase increased and was elevated (P < 0.001) compared with baseline in all groups, with values returning to baseline in the physical activity and combination groups by 48 h. However, creatine kinase in the control and ibuprofen groups was still significantly higher than at baseline after 48 h. Creatine kinase was higher (P < 0.001) in the control group than in physical activity and combination groups at 24 and 48 h. There was also a reduction (P < 0.001) in elbow range of motion across time. This reduction in elbow range of motion was greater (P < 0.001) in the control and ibuprofen groups than in the physical activity and combination groups at 1, 24 and 48 h. The reduction in maximum eccentric contraction was greater (P < 0.001) in the control and ibuprofen groups than in the physical activity group at 24 and 48 h and the combination group at 48 h. In conclusion, the results add to our understanding of the effects of physical activity and the combination of physical activity and ibuprofen in reducing the severity of muscle soreness induced by eccentric exercise. Physical activity conducted before eccentric exercise alleviates muscle soreness. Our results indicate that physical activity with or without ibuprofen helps to prevent delayed-onset muscle soreness.