Akiyoshi Okada

Water-based exercise improves health- related aspects of fitness in older women

PURPOSE The purpose of this study was to determine the physiological responses of elderly women to a well-rounded exercise program performed in water (WEX). METHODS The participants (60-75 yr of age) were randomly divided into a training (TR) group (N = 15) and a control group (N = 15). The TR group participated in a 12-wk supervised WEX program, 70 min x day(-1), 3 d x wk(-1). The WEX consisted of 20 min of warm-up and stretching exercise, 10 min of resistance exercise, 30 min of endurance-type exercise (walking and dancing), and 10 min of cool-down exercise. RESULTS The WEX led to an increase (P < 0.05) in peak VO2 (12%) and VO2 at lactate threshold (20%). Muscular strength evaluated by a hydraulic resistance machine increased significantly at resistance dial setting 8 (slow) for knee extension (8%), knee flexion (13%), chest press (7%) and pull (11%), shoulder press (4%) and pull (6%), and back extension (6%). Vertical jump (9%), side-stepping agility (22%), trunk extension (11%), and FEV1.0 (7%) also increased significantly. There was a significant decrease in skin-fold thickness (-8%), low-density lipoprotein (LDL) cholesterol (-17%), and total cholesterol (-11%). There were no significant changes in these variables in the control group. CONCLUSION These results indicate that WEX elicits significant improvements in cardiorespiratory fitness, muscular strength, body fat, and total cholesterol in older adult women. Water-based exercise appears to be a very safe and beneficial mode of exercise that can be performed as part of a well-rounded exercise program.

Difference in human cardiovascular response between upright and supine recovery from upright cycle exercise

Abstract Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (fc) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions. The average fc at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis) in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line – mean R-R interval = 0.006 × HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in fc following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography) decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar to that at rest before exercise. The resultant cardiac output (Q˙c) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Q˙c were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated with fc, SV, Q˙c, and TPR during rest and recovery in different body positions.

Circadian rhythms of atrioventricular conduction properties in chronic atrial fibrillation with and without heart failure.

OBJECTIVES We examined the circadian variations in atrioventricular (AV) conduction properties during atrial fibrillation (AF) by a technique based on the Lorenz plot of successive ventricular response (VR) intervals and analyzed their relations with clinical features. BACKGROUND The VR interval in chronic AF shows circadian variation, which is attenuated in patients with an increased risk of death. Although the VR interval is determined by the dynamic processes in the AV node randomly stimulated by rapid atrial activity, the circadian variations of the AV conduction properties related to this mechanism are unknown. METHODS In 48 patients with chronic AF, Lorenz plots were generated on overlapping sequential segments of 512 VR intervals in 24-h ambulatory electrocardiograms. For each scatter plot, the 1.0-s intercept of the lower envelope (LE1.0) of the plot and the degree of scatter above the envelope (root mean square difference from the envelope [scattering index]) were measured for estimating AV node refractoriness and concealed AV conduction, respectively. RESULTS In all patients, a significant circadian rhythm was observed for the average VR interval, LE1.0 and scattering index, with an acrophase occurring at night. The mesor, amplitude and acrophase of LE1.0 and the scattering index closely and independently correlated with the corresponding rhythm variables of the average VR interval (partial r2 0.98, 0.86 and 0.68 for LE1.0 and 0.98, 0.92 and 0.92 for scattering index). The amplitudes of these measures were lower in patients with congestive heart failure (CHF) even after adjustment for the effects of age, duration of AF, medications, left atrial diameter and blood pressure (p < 0.01 for all). CONCLUSIONS These results suggest that 1) both AV node refractoriness and the degree of concealed AV conduction during AF may show a circadian rhythm; 2) the circadian rhythms of these properties may independently contribute to the circadian variation of the VR interval; and 3) these circadian rhythms may be attenuated in patients with CHF.

Spectral characteristics of ventricular response to atrial fibrillation

To investigate the spectral characteristics of the fluctuation in ventricular response during atrial fibrillation (AF), R-R interval time series obtained from ambulatory electrocardiograms were analyzed in 45 patients with chronic AF and in 30 age-matched healthy subjects with normal sinus rhythm (SR). Although the 24-h R-R interval spectrum during SR showed a 1/f noise-like downsloping linear pattern when plotted as log power against log frequency, the spectrum during AF showed an angular shape with a breakpoint at a frequency of 0.005 +/- 0.002 Hz, by which the spectrum was separated into long-term and short-term components with different spectral characteristics. The short-term component showed a white noise-like flat spectrum with a spectral exponent (absolute value of the regression slope) of 0.05 +/- 0.08 and an intercept at 10(-2) Hz of 4.9 +/- 0.3 log(ms2/Hz). The long-term component had a 1/f noise-like spectrum with a spectral exponent of 1.26 +/- 0.40 and an intercept at 10(-4) Hz of 7.0 +/- 0.3 log(ms2/Hz), which did not differ significantly from those for the spectrum during SR in the same frequency range [spectral exponent, 1.36 +/- 0.06; intercept at 10(-4) Hz, 7.1 +/- 0.3 log(ms2/Hz)]. The R-R intervals during AF may be a sequence of uncorrelated values over the short term (within several minutes). Over the longer term, however, the R-R interval fluctuation shows the long-range negative correlation suggestive of underlying regulatory processes, and spectral characteristics indistinguishable from those for SR suggest that the long-term fluctuations during AF and SR may originate from similar dynamics of the cardiovascular regulatory systems.

Reduced Ventricular Response Irregularity Is Associated With Increased Mortality in Patients With Chronic Atrial Fibrillation

BACKGROUND-Variations in the ventricular response interval (VRI) during atrial fibrillation (AF) may be reduced in patients with adverse clinical outcomes. The properties of VRI dynamics associated with prognosis remain undetermined. METHODS AND RESULTS-In 107 patients with chronic AF (age, 64+/-9 years), we analyzed a 24-hour ambulatory ECG for VRI variability (SD, SD of successive differences, and SD of 5-minute averages) and VRI irregularity (Shannon entropy of histogram, symbolic dynamics, and approximate entropy of beat-to-beat and minute-to-minute fluctuations [ApEn(b-b) and ApEn(m-m)]). During a follow-up period of 33+/-16 months, 18 patients died (17%), 9 from cardiac causes, 7 from fatal strokes, and 2 from malignancies. Reductions in all VRI variability and irregularity measures were associated with an increased risk for cardiac death but not for fatal stroke. A significant association with cardiac death was also found for ejection fraction (relative risk, 1.10; 95% confidence interval [CI], 1.04 to 1.17, per 1% decrement) and ischemic AF (relative risk, 6.52; 95% CI, 1.62 to 26. 3). After adjustment for these clinical variables, all irregularity measures except symbolic dynamics had predictive value (relative risks [95% CIs] per 1SD decrement: Shannon entropy of histogram, 2. 03 [1.14 to 3.61]; ApEn(b-b), 1.72 [1.14 to 2.60]; and ApEn(m-m), 1. 90 [1.03 to 3.52]); however, the predictive power of variability measures was no longer significant. When the patients were stratified with the 33rd and 67th percentile values of ApEn(b-b) (1. 83 and 1.94, respectively), the 5-year cardiac mortality rates for the upper, middle, and lower tertiles were 0%, 13%, and 43%, respectively (log-rank test, P=0.04). CONCLUSIONS-Reduced VRI irregularity in a 24-hour ambulatory ECG has an independent prognostic value for cardiac mortality during long-term follow-up in patients with chronic AF.

Blood Pressure and Heart Rate Variability in Taxi Drivers on Long Duty Schedules

Blood Pressure and Heart Rate Variability in Taxi Drivers on Long Duty Schedules: Fumio KObayashi, et al. Department of Health and Psychosocial Medicine, Aichi Medical University School of Medicine

Aging and spectral characteristics of the nonharmonic component of 24-h heart rate variability

To examine whether heart rate variability (HRV) during daily life shows power law behavior independently of age and interindividual difference in the total power, log-log scaled coarse-graining spectra of the nonharmonic component of 24-h HRV were studied in 62 healthy men (age 21-79 yr). The spectra declined with increasing frequency in all subjects, but they appeared as broken lines slightly bending downward, particularly in young subjects with a large total power. Regression of the spectrum by a broken line with a single break point revealed that the spectral exponent (β) was greater in the region below than above the break point (1.63 ± 0.23 vs. 0.96 ± 0.21, P < 0.001). The break point frequency increased with age ( r = 0.51, P < 0.001) and β correlated with age negatively below the break point ( r = 0.39) and positively above the break point ( r = 0.70). The contribution to interindividual difference in total power was greater from the differences in the power spectral density at frequencies closer to both ends of the frequency axis and minimal from that at -3.25 log(Hz), suggesting hingelike movement of the spectral shape at this frequency with the difference in total power. These characteristics of the 24-h HRV spectrum were simulated by an artificial signal generated by adding two noises with different β values. Given that the power law assumption is fundamental to the analysis of dynamics through the log-log scaled spectrum, our observations are substantial for physiological and clinical studies of the heartbeat dynamic during daily life and suggest that the nonharmonic component of HRV in normal subjects during daily life may include at least two 1/ f β fluctuations that differ in dynamics and age dependency.To examine whether heart rate variability (HRV) during daily life shows power law behavior independently of age and interindividual difference in the total power, log-log scaled coarse-graining spectra of the nonharmonic component of 24-h HRV were studied in 62 healthy men (age 21-79 yr). The spectra declined with increasing frequency in all subjects, but they appeared as broken lines slightly bending downward, particularly in young subjects with a large total power. Regression of the spectrum by a broken line with a single break point revealed that the spectral exponent (beta) was greater in the region below than above the break point (1.63 +/- 0. 23 vs. 0.96 +/- 0.21, P < 0.001). The break point frequency increased with age (r = 0.51, P < 0.001) and beta correlated with age negatively below the break point (r = 0.39) and positively above the break point (r = 0.70). The contribution to interindividual difference in total power was greater from the differences in the power spectral density at frequencies closer to both ends of the frequency axis and minimal from that at -3.25 log(Hz), suggesting hingelike movement of the spectral shape at this frequency with the difference in total power. These characteristics of the 24-h HRV spectrum were simulated by an artificial signal generated by adding two noises with different beta values. Given that the power law assumption is fundamental to the analysis of dynamics through the log-log scaled spectrum, our observations are substantial for physiological and clinical studies of the heartbeat dynamic during daily life and suggest that the nonharmonic component of HRV in normal subjects during daily life may include at least two 1/fbeta fluctuations that differ in dynamics and age dependency.

Influence of cool-down exercise on autonomic control of heart rate during recovery from dynamic exercise.

The recovery of post-exercise heart rate (HR) is enhanced by a procedure of cooling down; however, the mechanism of this facilitated reduction is unknown. To determine whether more cardiac vagal reactivation is associated with a decrease in HR following cool-down exercise, we examined high-frequency R-R interval variability (HF, 0.15-0.40 Hz), an index of cardiac vagal tone, in six young healthy male subjects with a comparison between sitting rest after 6 minutes of cool-down cycling at 20% peak oxygen uptake (VO2peak) and sitting complete rest, following 5 min of upright cycle exercise at 70% VO2peak. During the last minute of exercise, there was no difference in HR between the two exercise tests before performing or not performing cool-down exercise (mean +/- SE, 148.7 +/- 6.9 versus 149.7 +/- 7.0 beats/min, respectively, by a Wilcoxon signed-ranks test). After exercise, a similar initial rapid decrease in HR and subsequent decline was observed during the first 6 min of recovery, regardless of cool-down exercise. However, the resting HR average following cool-down exercise was significantly lower than the corresponding HR without cool-down exercise (92.1 +/- 3.0 versus 100.8 +/- 3.6 beats/min, P < 0.05). The corresponding HF amplitude was slightly, but significantly greater with than without cool-down exercise (10.6 +/- 2.2 versus 9.0 +/- 1.9, P < 0.05). Thus the increase in HF amplitude corresponded to a decrease in resting HR following cool-down exercise, as compared to complete rest without cool-down exercise. Therefore, we conclude that after moderate exercise, the decrease in resting HR following cool-down exercise is associated with an increase in cardiac vagal tone.

Comparison of water- and land-based exercise in the reduction of state anxiety among older adults.

This study examined the effect of an acute exercise program of different exercise conditions on state anxiety among older adults. 73 healthy subjects were recruited and randomly assigned to either water exercise group (n = 36) or land exercise group (n = 37). State anxiety was assessed before exercise and following exercise. Subjects in the water exercise performed a 70-min. exercise program consisting of a 10-min. warm-up, a 20-min. brisk walking, a 20-min. rhythmic dancing, a 10-min. resistance training, and a 10-min. cool down exercise. The land exercise program contained a 10-min. warm-up and a 30-min. combined endurance and resistance exercise, followed by a 10-min. cool down exercise. Analysis showed that both exercise groups scored significantly (p<.001) lower on anxiety after exercise, but there was no significant interaction for group by trial for scores on state anxiety. The data indicate that elderly persons who participate in these types of exercise report lower state anxiety.

Effects of Hydraulic-resistance Exercise on Strength and Power in Untrained Healthy Older Adults

Lee, S, Islam, MM, Rogers, ME, Kusunoki, M, Okada, A, and Takeshima, N. Effects of hydraulic-resistance exercise on strength and power in untrained healthy older adults. J Strength Cond Res 25(4): 1089-1097, 2011-The purpose of this study was to determine the efficacy of hydraulic-resistance exercise (HDRE) in improving strength and power in healthy older adults. Thirty-nine older adults (68.6 ± 4.9 years; 15 men, 24 women) were divided into a training group or control group (CON). Hydraulic-resistance exercise consisted of a 12-week supervised program, 50 min·d−1, 3 d·wk−1. Hydraulic-resistance exercise was used for 10 exercises: Chest press and pull, shoulder press and pull, low back flexion and extension squat, leg adduction/abduction, leg press, and elbow extension/flexion. The number of the sets and the hydraulic-resistance dial setting (D) were gradually increased in 3 stages during the 12-week program. Strength, rating of perceived exertion, and relative intensity during exercise increased significantly from stage to stage whereas repetition velocity decreased. Total work was higher in the second stage compared with the first but lower in the final stage because of reduced repetitions. Peak torque at D2 and D11 increased (p < 0.05) for knee extension (58 and 9%) and flexion (94 and 21%), chest press (35 and 12%) and pull (29 and 14%), shoulder press (14 and 18%) and pull (75 and 18%), and low back flexion (59 and 46%) and extension (84 and 34%). Peak power at D2 and D11 also increased (p < 0.05) for knee extension (140 and 26%) and flexion (96 and 36%), chest press (54 and 28%) and pull (62 and 23%), shoulder press (55 and 31%) and pull (159 and 30%), and low back flexion (177 and 127%) and extension (104 and 66%). There were no significant changes in the CON. Hydraulic-resistance exercise elicits significant improvements in strength and power in older adults. Therefore, HDRE is an effective form of resistance training that provides benefits using low and moderate intensity of training for older adults.