Shohei Onishi

Autonomic differences between athletes and nonathletes: spectral analysis approach

The purpose of this study was to assess the adaptive effects of endurance training on autonomic function in athletes with spectral analysis of cardiovascular variability signals. Continuous ECG, arterial blood pressure (ABP), and respiratory signals were recorded from 15 athletes (VO2max > 55 mL.min-1.kg-1) and 15 nonathletes (VO2max < 45 mL.min-1.kg-1) during 10 min at sitting position. Autonomic function was assessed by low frequency power (LF power: 0.06-0.14 Hz) and high frequency power (HF power: the region of the respiratory frequency based on respiratory spectrum) obtained from the autospectra of RR interval, systolic arterial pressure (SAP), and diastolic arterial pressure (DAP) variability signals. The spontaneous baroreflex sensitivity was evaluated by the moduli, BRSLF and BRSHF, of the transfer function between RR interval and SAP variability in LF and HF bands. The resting HR in athletes was significantly lower than that in nonathletes. The HF power, an index of parasympathetic activity, in RR interval spectra were significantly higher in athletes than in nonathletes. Meanwhile, the LF power (an indicator of sympathetic activities contributing to RR interval and of ABP variabilities) showed no significant difference between both groups, although that of athletes was slightly less than that of nonathletes. Also, BRSLF and BRSHF were not significantly different between athletes and nonathletes. These results indicate that endurance training results in the enhanced vagal activities in athletes, which may contribute in part to the resting bradycardia.

Aortic root dilatation among young competitive athletes: Echocardiographic screening of 1929 athletes between 15 and 34 years of age

BACKGROUND Aortic dilatation can be lethal for young competitive athletes. The prevalence among athletes is not known, however, and thus a reasonable approach to early recognition remains uncertain. METHODS AND RESULTS Echocardiograms of 1929 normotensive athletes 15 to 34 years of age were analyzed. Five (0.26%) athletes had aortic dilatation; 4 of the 5 played basketball. This made the prevalence of aortic dilatation 0.96% (4 of 415) among basketball and volleyball players, who represented a population of especially tall athletes. Tallness aside, only 2 of the 5 athletes had features of Marfan syndrome. Among the athletes without aortic dilatation, the relation between body surface area and aortic root dimension was nonlinear and best described with a quadratic regression model. Athletes with aortic dilatation fell well outside the 95% confidence interval. CONCLUSION Because a higher incidence of aortic dilatation is to be anticipated among very tall athletes, inclusion of echocardiography in screening before participation in certain sports should be considered.

Relation between grip strength and radial bone mineral density in young athletes

In this study, we evaluated the relationship between bone mineral density (BMD) and muscle strength in young athletes who had not yet experienced age-related bone loss. Radial BMD and grip strength were measured in 10 male college wrestlers, 16 female college basketball players, and 12 female college tennis players. Radial BMD was measured in the distal and middle radius by dual energy x-ray absorptiometry (DEXA). Isometric grip strength was assessed with a hand-held dynamometer. The dominant forearm was examined in the amateur wrestlers and basketball players for grip strength and BMD. Both forearms were examined in the tennis players. A significant positive correlation was found between radial BMD and grip strength in the dominant forearm, and between radial BMD and body weight. Moreover, to eliminate a possible effect of body weight on radial BMD, we compared radial BMD with grip strength in both the dominant and nondominant arm of 12 college tennis players. Grip strength in the dominant forearm was significantly greater than in the nondominant forearm. The midradial BMD of the dominant forearm was also significantly higher than in the nondominant forearm. Based on these findings, we conclude that grip strength is one of the determinant factors of radial BMD in the dominant forearm of young college athletes.

Kinematical Analysis of Underwater Walking and Running

The purpose of this study was to determine kinematical characteristics of underwater locomotion and to compare them with those of land locomotion. Six male subjects performed walking and running on both conventional and underwater treadmills. Both treadmill speeds increased incrementally starting from 0.56 m s 1 to 3.33 m s 1, the maximum speed of the underwater treadmill. The motion analysis showed that underwater locomotion is characterized by the following points: (a) A transition from walking (1.11 m s 1) to running occurs at a lower speed in water; (b) stride frequency is significantly lower in water; (c) in order to reduce the hydrodynamic resistance of water, a greater knee joint flexion is used to reduce the trajectory area enclosed by the legs as the treadmill speed is increased; and (d) many kinematical differences were observed above a walking speed of 1.11 m s 1, also above this speed oxygen uptake was significantly higher in water. In water, the strategy of locomotion is quite different from that on land.

Unusual left ventricular dilatation without functional or biochemical impairment in normotensive extremely overweight Japanese professional sumo wrestlers

To explore the physiologic limit of left ventricular (LV) enlargement, we performed echocardiography and air displacement plethysmography to respectively assess LV dimension and function and the body composition of Japanese professional sumo wrestlers. After excluding subjects with cardiovascular disease, hypertension, plasma brain natriuretic peptide (BNP) > or =17.9 pg/ml, diabetes mellitus, or asthma, 331 subjects (mean +/- SD age, 21.6 +/- 3.7 years; height 179.2 +/- 5.3 cm; weight 1,17.9 +/- 21.5 kg; percent fat, 29.6 +/- 6.6%) were analyzed. LV end-diastolic dimension averaged 58.4 +/- 3.7 mm and was within the generally regarded normal limit (< or =54 mm) in 14.5% of subjects, but was > or =60 mm in 41.1% of subjects. LV septal and posterior wall thicknesses were 10.3 +/- 0.9 and 10.2 +/- 0.9 mm, respectively. Peak E- and A-wave velocities, E/A ratio, LV fractional shortening, and BNP were 96 +/- 16 and 51 +/- 13 cm/s, 2.0 +/- 0.7, 33.5 +/- 4.5%, and 3.1 +/- 3.7 pg/ml, respectively. LV end-diastolic dimension was not correlated with these indexes of LV function or with plasma BNP levels, but was significantly correlated with height, weight, body surface area, fat-free mass, and fat mass. These results show that among very large, highly trained, professional athletes, LV end-diastolic dimension frequently exceeds the traditionally accepted upper limit of normal for the general population. This increase in LV end-diastolic dimension may thus represent an extreme example of the physiologic adaptation of the athletes heart.

Peak aerobic performance and left ventricular morphological characteristics in university students

ObjectiveTo determine whether a relationship exists between left ventricular morphology and aerobic capacity in large numbers of male university students with a physically inactive and active life style. DesignA prospective study. SettingSports medicine research center. ParticipantsEleven sedentary normal-weight university students, 17 sedentary overweight university students, and 215 university athletes. Main Outcome MeasuresAfter the echocardiographic examination, an incremental treadmill exercise test until exhaustion was performed to measure peak oxygen uptake (VO2). ResultsIn sedentary students, absolute peak VO2 in the overweight students was slightly higher than that in normal-weight students (3,024 vs. 2,912 ml/min). Relative peak VO2 (ml/min/kg) was highly negatively correlated with body mass index (kg/m2) in a total of 28 sedentary students. The correlation between absolute peak VO2 and left ventricular dimension was weak in the sedentary overweight students; however, a correlation coefficient of 0.55 was obtained in athletic students. A stepwise multiple regression showed significant determinants of absolute peak VO2 in athletic students for body surface area (45%), left ventricular dimension (7%), and certain sports (6%). ConclusionsA physically active life style plays a role in increasing both aerobic capacity and left ventricular enlargement. Body size appeared to be a potent stimulus to left ventricular enlargement.

Recognition of left ventricular hypertrophy in new recruits of professional sumo wrestling

The efficacy of electrocardiography (ECG) in the diagnosis of left ventricular (LV) hypertrophy in 890 males, newly recruited to Japanese professional sumo wrestling (15.9 +/- 1.8 years of age, 177.8 +/- 4.7cm, 107.3 +/- 4.7kg), was tested by comparing simple, widely employed ECG criteria (Sokolow-Lyon chest and limb lead voltages and Cornell voltage with repolarisation criteria) with echocardiographic evaluations of LV mass indexed to body surface area. LV hypertrophy was defined as a LV mass index > 2 SD above the mean value obtained from 115 age-matched, normotensive, sedentary, male controls. The prevalence of LV hypertrophy as determined by echocardiography was 9.0% the entire group and was 8.3% among the 484 normotensives. The sensitivities of the three ECG criteria were < or = 36.0%, and their specificities were 70.0-99.0%. In contrast to the Sokolow-Lyon chest lead criteria, the diagnostic performance of the Cornell criteria was little affected by body mass index (BMI), and stepwise regression revealed that BMI did not significantly correlate with Cornell voltage. Still, the diagnostic efficacy of ECG was not sufficient to merit its use for primary recognition of LV hypertrophy among professional sumo wrestlers. Indeed, LV hypertrophy will likely go undetected by ECG in most overweight muscular athletes.

Period of adolescence during which exercise maximizes bone mass in young women

The aim of this cross-sectional study was to investigate the age at which exercise exerted a favorable effect on peak bone mass in young women. The subjects were 24 college athletes (CA), 19 sedentary college students (CN), and 29 high school athletes (HA). Athletes participated in at least 9 h of exercise per week. Lumbar bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA). The history of exercise in puberty and adolescence was estimated by a questionnaire as to weekly participation in exercise, for example, field hockey, basketball, tennis, or soccer. The CA group showed significantly higher lumbar BMD than the CN or HA group (1.230 ± 0.112g/cm2vs 1.164 ± 0.120g/cm2 orvs 1.164 ± 0.088g/cm2;P < 0.05). In both the CA and CN groups, those who had a history of exercise during junior high school showed a significantly higher BMD regardless of the history of high school exercise. In the HA group, those who had exercised during junior high school also showed a significantly higher lumbar BMD than those who had not. These data suggested that exercise during junior high school has a favorable effect on peak bone mass, regardless of the history of high school exercise.

Power spectral analysis of lumbar muscle electromyogram in chronic low-back pain patients during dynamic trunk exercise

The purpose of this study was to investigate the pattern of lumbar muscle fatigue at spinal level during repeated dynamic trunk flexion and extension exercise in chronic low-back pain (CLBP) patients and in control subjects without back pain. The authors used a lumbar extension machine which is designed to isolate lumbar extension functions. The electromyogram (EMG) signal from erector spinae muscles at lumbar 1 (L1), L3 and L5 spinal level was detected by surface electrodes. Subjects were required to perform one set of variable resistance lumbar extensions through a 72/spl deg/ range of motion (ROM) with a weight load that allowed 13 repetitions of fatigue contraction. Median frequency (MF) of the EMG power spectrum was analyzed to compare fatigue. The experimental results indicated: (1) each lumbar muscle has a characteristic initial MF (IMF); (2) the IMF of each lumbar level showed no significant difference between the CLBP and control groups; (3) there were significant differences in the decreasing ratio of MF between L1, L3 and L5 in both groups; (4) the decreasing ratio of MF at L5 in the CLBP group was significantly higher than the control group.

Effects of 3 months of non-weight-bearing cycle ergometric exercise on bone metabolism

We evaluated the effect of non-weight-bearing exercise on bone metabolism by measuring serum levels of biochemical markers, N-terminal osteocalcin (OC), and intact OC. N-terminal assay using the radioimmunoassay (RIA) method is considered to be a marker of bone turnover. Intact OC was measured as a marker of bone formation by the sandwich enzyme-linked immunosorbent assay (ELISA) method. As is commonly known, the cycle ergometer is a very popular and useful tool for aerobic exercise used world wide to improve health. In this study, we evaluated the effect of such common exercise on N-terminal OC and intact OC using a cycle ergometer. N-terminal OC was not significantly changed after 30min of aerobic training with a cycle ergometer three times a week for 3 months, whereas intact OC decreased significantly. No changes in bone mineral density of weight-bearing or non-weight-bearing bones were found. These results suggest that the type and duration of exercise using the current training method were insufficient to produce a favorable effect on bone. The current training method consisted of aerobic, non-weight-bearing exercise alone using a cycle ergometer. It is unknown whether the non-weight-bearing form of exercise was responsible for our results, or whether the aerobic exercise itself was insufficient. The 3-month period may have been insufficient to stimulate osteogenesis, and it is possible that an exercise period of this duration may instead result in a tendency to suppress bone formation. At any rate, we believe it is significant that we were able to demonstrate, on the basis of changes in bone metabolism markers and bone mineral density, that the nature of this exercise was insufficient to stimulate osteogenesis.