KEN-ICHI NEMOTO, MS; HIROKAZU GEN-NO, PHD; SHIZUE MASUKI, PHD; KAZUNOBU OKAZAKI, PHD; AND HIROSHI NOSE, MD, PHD OBJECTIVE: To examine whether high-intensity interval walking training increased thigh muscle strength and peak aerobic capacity and reduced blood pressure more than moderateintensity continuous walking training. From May 18, 2004, to October 15, 2004 (5-month study period), 60 men and 186 women with a mean ± SD age of 63±6 years were randomly divided into 3 groups: no walking training, moderate-intensity continuous walking training, and high-intensity interval walking training. Participants in the moderate-intensity continuous walking training group were instructed to walk at approximately 50% of their peak aerobic capacity for walking, using a pedometer to verify that they took 8000 steps or more per day for 4 or more days per week. Those in the high-intensity interval walking training group, who were monitored by accelerometry, were instructed to repeat 5 or more sets of 3-minute low-intensity walking at 40% of peak aerobic capacity for walking followed by a 3-minute high-intensity walking above 70% of peak aerobic capacity for walking per day for 4 or more days per week. Isometric knee extension and flexion forces, peak aerobic capacity for cycling, and peak aerobic capacity for walking were all measured both before and after training. PARTICIPANTS AND METHODS: RESULTS:The targets were met by 9 of 25 men and 37 of 59 women in the no walking training group, by 8 of 16 men and 43 of 59 women in the moderate-intensity continuous walking training group, and by 11 of 19 men and 31 of 68 women in the highintensity interval walking training group. In the high-intensity interval walking training group, isometric knee extension increased by 13%, isometric knee flexion by 17%, peak aerobic capacity for cycling by 8%, and peak aerobic capacity for walking by 9% (all, P<.001), all of which were significantly greater than the increases observed in the moderate-intensity continuous walking training group (all, P<.01). Moreover, the reduction in resting systolic blood pressure was higher for the high-intensity interval walking training group (P=.01).CONCLUSION: High-intensity interval walking may protect against age-associated increases in blood pressure and decreases in thigh muscle strength and peak aerobic capacity.

Chronic moderate exercise has been reported to reduce pro-inflammatory cytokines. To analyze the molecular mechanisms by which training exerts these effects, the epigenetic influences of age and exercise on the ASC gene, which is responsible for IL-1β and IL-18 secretion, were investigated by ASC gene methylation. Further, the relationship between carcinogenesis and exercise, methylation of the p15 tumor suppressive gene was analyzed as well. High-intensity interval walking exercise, consisting of 3-minute low-intensity walking at 40% of peak aerobic capacity followed by a 3-minute high-intensity walking period above 70% of peak aerobic capacity, was continued for 6 months. Peripheral blood DNA extracts from young control (n=34), older control (n=153), and older exercise (n=230) groups were then analyzed by pyrosequencing for DNA methylation. Methylation of ASC decreased significantly with age (young control vs. older control, p<.01), which is indicative of an age-dependent increase in ASC expression. Compared to the older control group, the degree of ASC methylation was higher in the older exercise group (older control vs. older exercise:, p<.01) and presumably lower ASC expression. Neither exercise nor age affected the methylation of the p15. In summary, chronic moderate exercise appears to attenuate the age-dependent decrease in ASC methylation, implying suppression of excess pro-inflammatory cytokines through reduction of ASC expression.

We assessed the effects of aerobic and/or resistance training on thermoregulatory responses in older men and analyzed the results in relation to the changes in peak oxygen consumption rate (VO(2 peak)) and blood volume (BV). Twenty-three older men [age, 64 +/- 1 (SE) yr; VO(2 peak), 32.7 +/- 1.1 ml. kg(-1). min(-1)] were divided into three training regimens for 18 wk: control (C; n = 7), aerobic training (AT; n = 8), and resistance training (RT; n = 8). Subjects in C were allowed to perform walking of ~10,000 steps/day, 6-7 days/wk. Subjects in AT exercised on a cycle ergometer at 50-80% VO(2 peak) for 60 min/day, 3 days/wk, in addition to the walking. Subjects in RT performed a resistance exercise, including knee extension and flexion at 60-80% of one repetition maximum, two to three sets of eight repetitions per day, 3 days/wk, in addition to the walking. After 18 wk of training, VO(2 peak) increased by 5.2 +/- 3.4% in C (P > 0.07), 20.0 +/- 2.5% in AT (P < 0.0001), and 9.7 +/- 5.1% in RT (P < 0.003), but BV remained unchanged in all trials. In addition, the esophageal temperature (T(es)) thresholds for forearm skin vasodilation and sweating, determined during 30-min exercise of 60% VO(2 peak) at 30 degrees C, decreased in AT (P < 0.02) and RT (P < 0.02) but not in C (P > 0.2). In contrast, the slopes of forearm skin vascular conductance/T(es) and sweat rate/T(es) remained unchanged in all trials, but both increased in subjects with increased BV irrespective of trials with significant correlations between the changes in the slopes and BV (P < 0.005 and P < 0.0005, respectively). Thus aerobic and/or resistance training in older men increased VO(2 peak) and lowered T(es) thresholds for forearm skin vasodilation and sweating but did not increase BV. Furthermore, the sensitivity of the increase in skin vasodilation and sweating at a given increase in T(es) was more associated with BV than with VO(2 peak).

We examined the effect of increased plasma osmolality (P(osm)) on cutaneous vasodilatory response to increased esophageal temperature (T(es)) in passively heated human subjects (n = 6). To modify P(osm), subjects were infused with 0.9, 2, or 3% NaCl infusions (Inf) for 90 min on separate days. Infusion rates were 0.2, 0.15, and 0.125 ml.min-1.kg body wt-1 for 0.9, 2, and 3% Inf, respectively, which produced relatively similar plasma volume expansion. Thirty minutes after the end of infusion, subjects immersed their lower legs in a water bath at 42 degrees C (room temperature 28 degrees C) for 60 min after 10 min of preheating control measurements. Passive heating without infusion (NI) served as time control to account for the effect of volume expansion. P(osm) (mosmol/kgH2O) values at the onset of passive heating were 289.9 +/- 1.4, 292.1 +/- 0.6, 298.7 +/- 0.7, and 305.6 +/- 0.6 after NI, 0.9% Inf, 2% Inf, and 3% Inf, respectively. The increases in T(es) (delta T(es)) at equilibrium during passive heating (mean delta T(es) during 55-60 min) were 0.47 +/- 0.08, 0.59 +/- 0.08, 0.85 +/- 0.13, and 1.09 +/- 0.12 degrees C after NI, 0.9% Inf, 2% Inf, and 3% Inf, respectively, which indicates that T(es) at equilibrium increased linearly as P(osm) increased. delta T(es) required to elicit cutaneous vasodilation (delta T(es) threshold for cutaneous vasodilation) also increased linearly as P(osm) increased as well as the delta T(es) threshold for sweating. The calculated increases in these thresholds per unit rise in P(osm) from regression analysis were 0.044 degree C for the cutaneous vasodilation and 0.034 degree C for sweating. Thus the delta T(es) thresholds for cutaneous vasodilation and sweating are shifted to higher delta T(es) along with the increase in P(osm), and these shifts resulted in the higher increase in T(es) during passive heating.