Shizue Masuki

Effects of High-Intensity Interval Walking Training on Physical Fitness and Blood Pressure in Middle-Aged and Older People

OBJECTIVE To examine whether high-intensity interval walking training increased thigh muscle strength and peak aerobic capacity and reduced blood pressure more than moderate-intensity continuous walking training. PARTICIPANTS AND METHODS 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. 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 high-intensity 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.

Reduced α-adrenoceptor responsiveness and enhanced baroreflex sensitivity in Cry-deficient mice lacking a biological clock

To reveal the role of clock genes in generating the circadian rhythm of baroreflexes, we continuously measured mean arterial pressure and baroreflex sensitivity in free‐moving normal wild‐type mice, and in Cry‐deficient mice which lack a circadian rhythm, in constant darkness for 24 h. In wild‐type mice the mean arterial pressure was higher at night than during the day, and was accompanied by a significantly enhanced baroreflex sensitivity of −13.6 ± 0.8 at night compared with −9.7 ± 0.7 beats min−1 mmHg−1 during the day (P < 0.001). On the other hand, diurnal changes in arterial pressure disappeared in Cry‐deficient mice with remarkably enhanced baroreflex sensitivity compared with wild‐type mice (P < 0.001): −21.9 ± 1.6 at night and −23.1 ± 2.1 beats min−1 mmHg−1 during the day. Moreover, the mean arterial pressure response to 10 μg kg−1 of phenylephrine, an α1‐adrenoceptor agonist, was severely suppressed in Cry‐deficient mice regardless of time, while that for the wild‐type mice was 10.1 ± 1.9 mmHg in the night, significantly lower than 22.0 ± 3.5 mmHg in the day (P < 0.01). These results suggest that CRY genes are involved in generating the circadian rhythm of baroreflex sensitivity, partially by regulating α1‐adrenoceptor‐mediated vasoconstriction in peripheral vessels.

POTS versus deconditioning: the same or different?

The 2007 Streeten Lecture focused on the idea that physical deconditioning plays a key role in the symptomology and pathophysiology of POTS. Parallels were drawn between the physiological responses to orthostatic stress seen in POTS patients and the physiological responses seen in “normal” humans after prolonged periods of bedrest, deconditioning, or space flight. Additionally, the idea that endurance exercise training might ameliorate some of these symptoms was also advanced. Finally, potential parallels between POTS, chronic fatigue syndrome, and fibromyalgia were also drawn and the potential role of exercise training as a “therapeutic intervention” in all three conditions was raised. The conceptual model for the lecture was that after some “initiating event” chronic deconditioning plays a significant role in the pathophysiology of these conditions, and these physiological changes in conjunction with “somatic hypervigilence” explain many of the complaints that this diverse group of patients have. Additionally, the idea that systematic endurance exercise training might be helpful was advanced, and data supportive of this idea was reviewed. The main conclusion is that the medical community must retain their empathy for patients with unusual conditions but at the same time send a firm but empowering message about physical activity. As always, we must also ask what do the ideas about physical activity and inactivity and the conditions mentioned above not explain?

A New Device to Estimate V˙O2 during Incline Walking by Accelerometry and Barometry

PURPOSE To examine whether the biased estimation of oxygen consumption rate (VO2, mL x kg(-1) x min(-1)) by accelerometry during incline walking can be improved by the addition of altitude changes as measured by barometry. METHODS We measured VO2 by respiratory gas analysis and vector magnitude (VM, G) from triaxial accelerations in 42 healthy people (mean +/- SD age = 63 +/- 7 yr) during graded walking on a treadmill while the incline was varied from -15% to +15%. They walked at subjectively slow, moderate, and fast speeds on level and uphill inclines and, in addition to these, at their fastest speed at 0% incline. They then walked at approximately 3, 4, and 5 km x h(-1) on downhill inclines for 3 min each. We determined a regression equation to estimate VO2 from VM and theoretical vertical upward (Hu, m x min(-1)) and downward speeds (Hd, m x min(-1)) for the last 1 min of each trial. To validate the precision of the equation, we measured VM and altitude changes with a portable device equipped with a triaxial accelerometer and a barometer in 11 of the 42 subjects walking on an outdoor hill and compared the estimated VO2 with the value simultaneously measured by respiratory gas analysis. RESULTS VO2 above resting was estimated from VO2 = 0.044 VM + 1.365 Hu + 0.553 Hd (r = 0.93, P < 0.001) and the estimated V O2(y) was almost identical to the measured VO2(x) (y = 0.97x, r = 0.88, P < 0.001) with a mean difference of -0.20 +/- 3.47 (mean +/- SD) by Bland-Altman analysis in the range of 2.0-33.0 mL x kg(-1) x min(-1). CONCLUSIONS VO2 during walking on various inclines can be precisely estimated by using the device equipped with a triaxial accelerometer and a barometer.

Impact of protein and carbohydrate supplementation on plasma volume expansion and thermoregulatory adaptation by aerobic training in older men

We examined whether protein-carbohydrate (CHO) supplementation immediately after exercise each day during aerobic training facilitated plasma volume (PV) expansion and thermoregulatory and cardiovascular adaptations in older men. Fourteen moderately active older men [68 +/- 5 (SD) yr] were divided into two groups so as to have no significant differences in anthropometric measures, PV, and peak oxygen consumption rate (Vo(2peak)). Each group was provided with a mixture of protein and CHO (3.2 kcal, 0.18 g protein/kg body wt, Pro-CHO, n = 7) or a non-protein and low-calorie placebo (0.5 kcal, 0 g protein/kg body wt, CNT, n = 7) immediately after cycling exercise (60-75% Vo(2peak), 60 min/day, 3 days/wk) each day for 8 wk at approximately 19 degrees C ambient temperature (T(a)) and approximately 43% relative humidity (RH). Before and after training, we measured PV, cardiac stroke volume (SV), and esophageal temperature (T(es)) during 20-min exercise at 60% of pretraining Vo(2peak) at 30 degrees C T(a) and 50% RH. Moreover, we determined the sensitivity of the chest sweat rate (DeltaSR/DeltaT(es)) and forearm vascular conductance (DeltaFVC/DeltaT(es)) in response to increased T(es) during exercise. After training, PV increased by approximately 6% in Pro-CHO (P < 0.001), with an approximately 10% increase in SV during exercise (P < 0.001), but not in CNT (P > 0.07). DeltaFVC/DeltaT(es) increased by 80% and DeltaSR/DeltaT(es) by 18% in Pro-CHO (both P < 0.01) but not in CNT (P > 0.07). Moreover, we found a significant interactive effect of group x training on PV, SV, and DeltaFVC/DeltaT(es) (all P < 0.02) but with no significant effect of group (P > 0.4), suggesting that the supplement enhanced these responses to aerobic training. Thus postexercise protein-CHO supplementation during training caused PV expansion and facilitated thermoregulatory and cardiovascular adaptations, possibly providing a new training regimen for older men.

Physical fitness and indices of lifestyle-related diseases before and after interval walking training in middle-aged and older males and females

Hypothesis Whether increasing peak aerobic capacity for walking (V̇2peak) by interval walking training (IWT) is closely linked with decreasing the indices of lifestyle-related diseases (LSDs) in middle-aged and older people were examined. Methods For 4 months from April to September 2005 or 2006, 246 males and 580 females (∼65 years) performed IWT consisting of ≥5 sets of fast walking at ≥70% V̇2peak for 3 min followed by slow walking at ≤40% V̇2peak for 3 min ≥4 days/week. Before and after IWT, we measured V̇2peak, body mass index (BMI), %body fat, arterial blood pressure, thigh muscle strength and blood parameters. We analysed 198 males and 468 females who had undergone all the measurements both before and after IWT. To examine the hypothesis, we divided the subjects equally into three groups according to their pretraining V̇2peak: low, middle and high groups for each sex. Results Before training, it was found that thigh muscle strength and blood high-density lipoprotein cholesterol concentration were lower, whereas body weight, BMI, %body fat, arterial blood pressure and blood glucose were higher in the low group than the high group (all, p<0.05). After training, although V̇2peak and thigh muscle strength increased and body weight, BMI, %body fat, blood pressure and blood glucose concentration decreased in all groups (all, p<0.05), the changes were greatest in the low group for both sexes. Conclusion V̇2peak at baseline and changes in response to training were closely linked with indices of LSDs.

Beyond epidemiology: field studies and the physiology laboratory as the whole world

There is no exercise training regimen broadly available in the field to increase physical fitness and prevent lifestyle‐related diseases in middle‐aged and older people. We have developed interval walking training (IWT) repeating five or more sets of 3 min fast walking at ≥70% peak aerobic capacity for walking (w) per day with intervening 3 min slow walking at 40% w, for ≥4 days week−1, for ≥5 months. Moreover, to determine w in individuals and also to measure their energy expenditure even while incline walking, we have developed a portable calorimeter. Further, to instruct subjects on IWT even if they live remotely from the trainers, we have developed e‐Health Promotion System. This transfers individual energy expenditure during IWT stored on the meter to a central server through the internet; it sends back the achievement to individuals along with advice generated automatically by the sever according to a database on ≥4000 subjects. Where we found that 5 months of IWT increased physical fitness and improved the indices of lifestyle‐related diseases by 10–20% on average. Since our system is run at low cost with fewer staff for more subjects, it enables us to develop exercise prescriptions appropriate for individuals.

Triaxial accelerometry to evaluate walking efficiency in older subjects.

PURPOSE We tested the suitability of triaxial accelerometry to evaluate walking efficiency in older subjects. METHODS First, we verified the accuracy to estimate the oxygen consumption rate (.VO2, mL.min-1) from the total impulse (Itotal, N.min-1), the square root of summed accelerations of each direction, during graded walking on a flat ground in 13 male and 27 female older subjects (61 +/- 6 yr, mean +/- SD). Second, to examine the effects of endurance/resistance training on walking efficiency, we assessed the relations of maximal isometric knee extension force (Fmax, N.m), maximal walking velocity (Vmax, m.min-1), and three-dimensional impulses (Ix, anterior-posterior; Iy, mediolateral; Iz, vertical) in 13 male and 40 female older subjects (62 +/- 7 yr) before and after 6 and 9 months of training. RESULTS The following analyses were performed in all the data from the male and female groups. First, .VO2 was highly correlated with Itotal (r = 0.958, P < 0.0001) over the range of 250-2200 mL.min-1. Second, Fmax and Vmax increased by 48 +/- 7% (P < 0.001) and 21 +/- 2% (P < 0.001), respectively, after 9 months of training. Ix/Itotal and Iy/Itotal increased by 18 +/- 2% (P < 0.001) and 10 +/- 2%, respectively, after 9 months of training (P < 0.001), whereas Iz/Itotal decreased by 14 +/- 2% (P < 0.001). Vmax was negatively correlated with Iz/Itotal (r = -0.522, P < 0.0001) while positively correlated with Ix/Itotal (r = 0.561, P < 0.0001) and Iy/Itotal in the pooled data from before, after 6 and 9 months of training. Similarly, the product of Vmax and body weight was positively correlated with Fmax (r = 0.633, P < 0.0001). CONCLUSIONS These results suggest that increased Fmax improved walking efficiency by increasing energy utilization in the anterior-posterior/mediolateral directions while decreasing energy loss in the vertical direction.

Effects of hypohydration on thermoregulation during exercise before and after 5-day aerobic training in a warm environment in young men

We examined whether enhanced cardiovascular and thermoregulatory responses during exercise after short-term aerobic training in a warm environment were reversed when plasma volume (PV) expansion was reversed by acute isotonic hypohydration. Seven young men performed aerobic training at the 70% peak oxygen consumption rate (Vo(₂peak)) at 30°C atmospheric temperature and 50% relative humidity, 30 min/day for 5 days. Before and after training, we performed the thermoregulatory response test while measuring esophageal temperature (T(es)), forearm skin vascular conductance, sweat rate (SR), and PV during 30 min exercise at the metabolic rate equivalent to pretraining 65% Vo(₂peak) in euhydration under the same environment as during training in four trials (euhydration and hypohydration, respectively). Hypohydration targeting 3% body mass was attained by combined treatment with low-salt meals to subjects from ~48 h before the test and administration of a diuretic ~4 h before the test. After training, the T(es) thresholds for cutaneous vasodilation and sweating decreased by 0.3 and 0.2°C (P = 0.008 and 0.012, respectively) when PV increased by ~10%. When PV before and after training was reduced to a similar level, ~10% reduction from that in euhydration before training, the training-induced reduction in the threshold for cutaneous vasodilation increased to a level similar to hypohydration before training (P = 0.093) while that for sweating remained significantly lower than that before training (P = 0.004). Thus the enhanced cutaneous vasodilation response after aerobic training in a warm environment was reversed when PV expansion was reversed while the enhanced SR response remained partially.

Protein and carbohydrate supplementation during 5-day aerobic training enhanced plasma volume expansion and thermoregulatory adaptation in young men

We examined whether protein and carbohydrate (CHO) supplementation during 5-day training enhanced plasma volume (PV) expansion and thermoregulatory and cardiovascular adaptations in young men. Eighteen men [age 23 ± 4 (SD) yr] were divided into two groups according to supplements: placebo (CNT: 0.93 kcal/kg, 0.00 g protein/kg, n = 9) and protein and CHO (Pro-CHO: 3.6 kcal/kg, 0.36 protein/kg, n = 9). Subjects in both groups performed a cycling exercise at 70% peak oxygen consumption rate (VO2peak), 30 min/day, for 5 consecutive days at 30°C ambient temperature and 50% relative humidity and took either a placebo or Pro-CHO within 10 min after exercise for each day. Before and after training, PV at rest, heart rate (HR), and esophageal temperature (T(es)) during 30-min exercise at 65% of pretraining VO2peak in the same condition as training were determined. Also, the sensitivity of the chest sweat rate (ΔSR/ΔT(es)) and forearm vascular conductance (ΔFVC/ΔT(es)) in response to increased T(es) were determined. After training, PV and cardiac stroke volume (SV) at rest increased in both groups (P < 0.001) but the increases were twofold higher in Pro-CHO than CNT (P = 0.007 and P = 0.078, respectively). The increases in HR from 5 to 30 min and T(es) from 0 to 30 min of exercise were attenuated after training in both groups with greater attenuation in Pro-CHO than CNT (P = 0.002 and P = 0.072, respectively). ΔSR/ΔT(es) increased in CNT (P = 0.052) and Pro-CHO (P < 0.001) and the increases were higher in Pro-CHO than CNT (P = 0.018). ΔFVC/ΔT(es) increased in Pro-CHO (P < 0.001), whereas not in CNT (P = 0.16). Thus protein-CHO supplementation during 5-day training enhanced PV expansion and thermoregulatory adaptation and, thereby, the reduction in heat and cardiovascular strain in young men.