A comparison of three bioelectrical impedance analyses for predicting lean body mass in a population with a large difference in muscularity

This study tested the hypothesis that, as compared to whole-body bioelectrical impedance (BI) analysis, segmental BI analysis can estimate lean body mass (LBM) more accurately in a population with a large difference in muscularity. In addition to whole-body BI, which determines impedance (Z) between the wrist and ankle, two segmental BI analyses which determine the Z value of every body segment in each of (1) the arms, legs and trunk (distal BI) and (2) the upper arms, upper legs and trunk (proximal BI) were applied to a group of 125 male athletes and 75 non-athletes. The subjects were divided into validation and cross-validation groups. Simple and multiple regression analyses were applied to (length)²/Z (BI index) values for the whole-body and each body segment, to develop the prediction equations of LBM measured using air-displacement plethysmography. In the validation group, the SE of estimation was similar in the whole-body (3.4 kg, 5.4%), distal (3.4 kg, 5.5%) and proximal BI (3.3 kg, 5.2%) analyses. However, the whole-body and distal BI analyses produced systematical errors in the estimates of LBM. Moreover, the residuals in the two methods significantly (P<0.05) correlated with the ratios of BI indices of the upper arms and upper legs to those of the arms and legs, respectively, calculated as variables approximating the relative development of lean tissues at the proximal area of limbs. On the other hand, the proximal BI analysis was validated and cross-validated. Thus, the accuracy of estimating LBM was similar in the whole-body and the two segmental BI analyses. However, the prediction equations derived from the use of the whole-body BI index and a combination of the arms, legs and trunk BI indices produced a systematical error relating to the difference between the limb segments in lean tissue development.     

Cardiorespiratory responses to exercise in acute hypoxia, hyperoxia and normoxia

There is a prevailing hypothesis that an acute change in the fraction of oxygen in inspired air (F _IO₂) has no effect on maximal cardiac output ( ), although maximal oxygen uptake ( ) and exercise performance do vary along with F _IO₂. We tested this hypothesis in six endurance athletes during progressive cycle ergometer exercise in conditions of hypoxia (F _IO₂=0.150), normoxia (F _IO₂=0.209) and hyperoxia (F _IO₂=0.320). As expected, decreased in hypoxia [mean (SD) 3.58 (0.45) l·min^–1, P<0.05] and increased in hyperoxia [5.17 (0.34) l·min^–1, P<0.05] in comparison with normoxia [4.55 (0.32) l·min^–1]. Similarly, maximal power ( ) decreased in hypoxia [334 (41) W, P<0.05] and tended to increase in hyperoxia [404 (58) W] in comparison with normoxia [383 (46) W]. Contrary to the hypothesis, was 25.99 (3.37) l·min^–1 in hypoxia (P<0.05 compared to normoxia and hyperoxia), 28.51 (2.36) l·min^–1 in normoxia and 30.13 (2.06) l·min^–1 in hyperoxia. Our results can be interpreted to indicate that (1) the reduction in in acute hypoxia is explained both by the narrowing of the arterio-venous oxygen difference and reduced , (2) reduced in acute hypoxia may be beneficial by preventing a further decrease in pulmonary and peripheral oxygen diffusion, and (3) reduced and in acute hypoxia may be the result rather than the cause of the reduced and skeletal muscle recruitment, thus supporting the existence of a central governor. Electronic Publication     

Pulmonary blood volume and interventricular circulation time in physically trained and untrained subjects

Summary Resting pulmonary plasma and blood volumes (PPV and PBV), interventricular circulation time (IVCT), cardiac and stroke index (CI and SI), heart rate (HR), total plasma and blood volumes (PV and BV) were determined in athletes (two male groups representing different types of sport activities, and one female group) and compared with those of non-athletes (one male and one female group).In addition to high maximal aerobic power, the athletes were characterized by greater SI, BV and PV and lower resting HR than non-athletes. PPV and PBV were significantly larger and IVCT significantly longer in the trained than in the untrained groups, probably reflecting an improved capacity of the pulmonary circulation. PPV as per cent of PV was almost equal in all the groups, indicating the same distribution of plasma between the pulmonary and systemic circulation. The data also indicate that total blood volume is an important determinant of the magnitude of the pulmonary vascular bed. The increased volume of flowing blood and increased stroke volume in athletes probably allows for a reduction in flow velocity and thereby a reduction in kinetic energy.     

Resting whole blood viscosity of elite rowers is related to performance

This study investigated the relationships between resting whole blood viscosity (WBV), haemoglobin concentration (HGB), haematocrit (HCT), and performance in 25 highly-trained national squad rowers (11 women and 14 men). The WBV and HGB were measured at rest prior to a 2500 m simulated race on a Concept rowing ergometer when performance (P) was measured by average velocity. A group of 12 rowers were measured on just one occasion, another 11 were measured twice with an intervening 5 weeks of continued training and 2 were measured three times, the third test after another 4 weeks. Regression analyses making simultaneous use of both intra- and interindividual data indicated a significant inverse relationship between P and WBV (at both high and low shear rates), a relationship which was strengthened after statistically controlling for the effects of HGB, this effect being slightly more significant than HCT. A significant positive regression also emerged between P and HGB, but only after statistically controlling for the influence of WBV at high shear rate. Overall, stronger relationships were demonstrated in the male rowers compared with the female. These data, in the light of previous evidence that fitter people tend to have lower WBV, would indicate that blood rheology unrelated to HGB (or HCT) is related to performance in relatively homogeneous and already highly-trained athletes.     

Maximal oxygen consumption,pulmonary function,body composition,and anthropometry of adolescent female athletes

Three groups of girl athletes — 10 gymnasts and 8 middle-distance swimmers averaging 14 years of age, and 8 middle-distance runners averaging almost 19 — were the subjects of this study. The maximal oxygen intake was determined by graded work load on a bicycle ergometer, certain pulmonary functions by spirometry, and total body potassium by wholebody counting of naturally radioactive⁴⁰K. The total body water was obtained from measurements of deuterium oxide and application of the dilution principle, and creatinine excretion was determined from urine collections. Fat-free mass was calculated from total body water, and the amount of body fat was obtained by subtracting fat-free mass from body weight. Cell mass was calculated from total body potassium. Supporting evidence of leanness or fatness was provided by anthropometric measurements.The runners and swimmers achieved significantly higher maximal oxygen consumption per kg of body weight, fat-free mass, and cell mass; and the runners excelled the gymnasts in certain other pulmonary functions. Total body potassium in milliequivalents per kg of body weight, total body water expressed in percentage of body weight, and creatinine coefficients were similar in all three groups of subjects. These results indicated no differences in body composition. Calculations of body fat, fat-free mass, and cellular mass verified that conclusion; and supporting evidence was obtained from subcutaneous fat folds and from appraisal of leanness by corrected limb diameters or volumes, which also were similar in all three groups.     

Serum hormones in male strength athletes during intensive short term strength training

Summary Training-induced adaptations in the endocrine system and strength development were investigated in nine male strength athletes during two separate 3-week intensive strength training periods. The overall amount of training in the periods was maintained at the same level. In both cases the training in the first 2 weeks was very intensive: this was followed by a 3rd week when the overall amount of training was greatly decreased. The two training periods differed only in that training period I included one daily session, while during the first 2 weeks of period II the same amount of training was divided between two daily sessions. In general, only slight and statistically insignificant changes occurred during training period I in mean concentrations of serum hormones examined or sex hormone-binding globulin as well as in maximal isometric leg extensor force. However, during training period II after 2 weeks of intensive strength training a significant decrease (P<0.05) was observed in serum free testosterone concentration [from 98.4 (SD 24.5) to 83.8 (SD 14.7) pmol · l^–1] during the subsequent week of reduced training. No change in the concentration of total testosterone was observed. This training phase was also accompanied by significant increases (P<0.05) in serum luteinizing hormone (LH) and cortisol concentrations. After 2 successive days of rest serum free testosterone and LH returned to (P<0.05) their basal concentrations. Training period II led also to a significant increase (P<0.05) [from 3942 (SD 767) to 4151 (SD 926) N] in maximal force. These findings suggest that in male strength athletes dividing the amount of training into smaller units may create more effective training stimuli leading to further strength development.     

Effects of resistance exercise combined with vascular occlusion on muscle function in athletes

The effects of resistance exercise combined with vascular occlusion on muscle function were investigated in highly trained athletes. Elite rugby players (n=17) took part in an 8 week study of exercise training of the knee extensor muscles, in which low-intensity [about 50% of one repetition maximum] exercise combined with an occlusion pressure of about 200 mmHg (LIO, n=6), low-intensity exercise without the occlusion (LI, n=6), and no exercise training (untrained control, n=5) were included. The exercise in the LI group was of the same intensity and amount as in the LIO group. The LIO group showed a significantly larger increase in isokinetic knee extension torque than that in the other two groups (P<0.05) at all the velocities studied. On the other hand, no significant difference was seen between LI and the control group. In the LIO group, the cross-sectional area of knee extensors increased significantly (P<0.01), suggesting that the increase in knee extension strength was mainly caused by muscle hypertrophy. The dynamic endurance of knee extensors estimated from the decreases in mechanical work production and peak force after 50 repeated concentric contractions was also improved after LIO, whereas no significant change was observed in the LI and control groups. The results indicated that low-intensity resistance exercise causes, in almost fully trained athletes, increases in muscle size, strength and endurance, when combined with vascular occlusion. Electronic Publication     

A pilot study using magnetic resonance imaging to determine the pattern of muscle group recruitment by rowers with different levels of experience

Objective. To determine whether it was possible using magnetic resonance imaging (MRI) to define the pattern of muscle recruitment in a specific sport (rowing) and to see whether there were differences in this pattern between athletes of different experience. Design and method. It has been shown that during vigorous exercise the water content of muscle increases transiently. This can be observed using MRI, where the prolonged T2 relaxation time of muscle can be demonstrated. In this study we have exploited the increase in signal seen in exercised muscle on short TI inversion recovery (STIR) sequences, to show how rowers of different experience use different muscle groups. Results.We have shown that trained athletes recruit selected muscle groups to carry out a given task, which they carry out more efficiently than untrained or less experienced athletes. Conclusion.We have provided the basis of potential research to refine training methods, in order to develop specific muscle groups in athletes, in the hope of achieving a higher level of performance at an earlier stage in their training. We have also defined a technique that may be of clinical value in cases of muscle dysfunction. Received: 13 September 1999 Revision requested: 19 November 1999 Revision received: 30 December 1999 Accepted: 4 January 2000