The Effect of Pedaling Cadence on Skeletal Muscle Oxygenation During Cycling at Moderate Exercise Intensity.

The aim of this study was to assess the changes determined by increased cadence on skeletal muscle oxygenation during cycling at an exercise intensity equal to the ventilatory threshold (Tvent).Nine healthy, active individuals with different levels of cycling experience exercised at a power output equal to Tvent, pedaling at cadences of 40, 50, 60, 70, 80 and 90 rpm, each for 4 min. Cadences were tested in a randomized counterbalanced sequence. Cardiopulmonary and metabolic responses were studied using an ECG for heart rate, and gas calorimetry for pulmonary oxygen uptake and carbon dioxide production. NIRS was used to determine the tissue saturation index (TSI), a measure of vastus lateralis oxygenation.TSI decreased from rest to exercise; the magnitude of this TSI reduction was significantly greater when pedaling at 90 rpm (-14±4%), compared to pedaling at 40 (-12±3%) and 50 (-12±3%) rpm (P=0.027 and 0.017, respectively). Albeit small, the significant decrease in ΔTSI at increased cadence recorded in this study suggests that skeletal muscle oxygenation is relatively more affected by high cadence when exercise intensity is close to Tvent.

Stair ascending-descending exercise accelerates the decrease in postprandial hyperglycemia more efficiently than bicycle exercise.

OBJECTIVE: Stair climbing-descending exercise (ST-EX) is a convenient method to increase exercise intensity. We compared the acute effect of ST-EX on lowering postprandial hyperglycemia with that of constant bicycle exercise (BI-EX) performed at the same heart rate (HR). RESEARCH DESIGN AND METHODS: Seven people with type 2 diabetes and seven with impaired glucose tolerance volunteered for this study. The step rate for ST-EX and work rate for BI-EX were individually determined to correspond to high-moderate to low-vigorous intensity (HR ~130 beats per minute). For the ST-EX trial, the subjects performed 16 repetitions of walking down one flight of stairs followed by climbing up to the starting point (~8 min in duration) 90 min after consuming a test meal. For the BI-EX trial, the subjects performed a constant pedaling exercise for the same duration at the same time after the meal. RESULTS: The reduction in blood glucose (BG) level between 90 and 105 min after a meal was significantly greater for ST-EX (-4.0±0.7mmol/L) than for BI-EX (-2.7±0.9mmol/L). The net reduction in BG between 90 and 105 min was also significantly greater for ST-EX (-3.2±0.7mmol/L) than for BI-EX (-2.0±0.6mmol/L). Serum insulin levels did not differ between the groups. Oxygen consumption for ST-EX was higher than that for BI-EX, but the blood lactate level and respiratory exchange ratio (RER) for ST-EX were lower than those for BI-EX. CONCLUSIONS: Compared with BI-EX performed at the same HR, ST-EX more rapidly decreased postprandial BG level with lower blood lactate and RER responses. A short bout of ST-EX may be clinically useful to acutely ameliorate BG levels after meals.

Repeated 3-minute stair climbing-descending exercise after a meal over 2 weeks increases serum 1,5-anhydroglucitol levels in people with type 2 diabetes.

[Purpose] The purpose of this study was to examine the hypoglycemic effect of a postprandial exercise program using brief stair climbing-descending exercise in people with type 2 diabetes. [Subjects and Methods] Seven males with uncomplicated type 2 diabetes (age 68.0 ± 3.7 years) performed two sets of stair climbing-descending exercise 60 and 120 min after each meal for the first 2 weeks but not for the following 2 weeks. Each set of exercise comprised 3-min of continuous repetition of climbing briskly to the second floor followed by slow waking down to the first floor in their home. A rest period of 1-2 min was allowed between each set. [Results] Serum 1,5-anhydroglucitol level was significantly higher by 11.5% at the end of the 2-week exercise period than at the baseline. By contrast, the 1,5-anhydroglucitol level at the end of the following 2-week period did not differ from the baseline value. Fasting blood glucose level and insulin resistance index at the end of the exercise period did not differ from the baseline value. [Conclusion] Repeated 3-min bouts of stair climbing-descending exercise after a meal may be a promising method for improving postprandial glycemic control in people with type 2 diabetes.

Stair climbing/descending exercise for a short time decreases blood glucose levels after a meal in people with type 2 diabetes.

OBJECTIVE: We examined whether stair climbing-descending exercise (ST-EX), a convenient method to increase physical activity in daily life, for a short period would acutely improve the postprandial blood glucose (BG) response in people with type 2 diabetes (T2D). METHODS: 16 people with T2D (age 65.4±1.1 years) participated in 2 separate sessions. After an overnight fast, each participant consumed a test meal and then kept resting for 180 min, except when performing each 3 min bout of ST-EX at 60 and 120 min after the meal (ST-EX session), or kept resting for 180 min (REST session). ST-EX comprised 6 continuous repetitions of climbing to the second floor (21 steps) at a rate of 80-110 steps/min followed by walking down slowly to the first floor at a free step rate. RESULTS: The BG at 60 min after the meal during the ST-EX session (immediately before the first ST-EX) did not differ from that during the REST session, but analysis of variance revealed a significant interaction between time and treatment (p<0.01). The BG at 150 min after the meal (30 min after the second ST-EX) was significantly lower than that during the REST session (p<0.01). The area under the curve was also 18% lower during the ST-EX session than during the REST session (p<0.05). The heart rate and blood lactate levels indicated that the actual intensity of ST-EX was 'hard'. In contrast, the rating of perceived exertion (RPE) indicated that the overall intensity of ST-EX was 'moderate' because of decreased RPE scores during descent. CONCLUSIONS: The present findings suggest that performing 3 min ST-EX 60 and 120 min after a meal may be a useful strategy to accelerate the decrease in postprandial BG levels in people with T2D.

Immediate effects of varying cadence in bicycle ergometry on characteristics of gait and lower extremity motor activity in frail older adults.

AIM: This study examined the immediate effects of a 5-min pedaling period with varying cadence (VC) on various dimensions of gait function in frail older adults. METHODS: Twenty frail older adults (mean age 77.2 years) were randomly assigned to one of two groups: the VC group or the constant cadence (CC) group. Each group performed bicycle ergometry for 5 min at 20 W. The CC group pedaled continuously at a CC of 50 rpm, while the VC group pedaled continuously at cadences of 45, 55, 65, 55, and 45 rpm, in this order, changing cadence every 60 s. Immediately before and after bicycle ergometry, the following measurements were carried out: gait performance, muscle activity (electromyographic analysis), and knee motion analysis. RESULTS: CC did not significantly affect any of the measured parameters. In contrast, the VC group showed improvement in all three parameters: an increase in normal gait speed and cadence (p < 0.01), a reduction in the activation period (p < 0.04) and CI-THIGH (antagonistic coactivation time between knee flexor and extensor muscles, p < 0.05), and an increase in maximum knee extension angular velocity (p < 0.01). CONCLUSION: A short period of VC bicycle ergometry with low work intensity was effective in immediately improving gait function in frail older adults.

A short bout of stair climbing-descending exercise attenuates postprandial hyperglycemia in middle-aged males with impaired glucose tolerance.

Exercise is a useful modality to ameliorate postprandial hyperglycemia. Here we show that a short bout (∼6 min) of stair climbing-descending exercise (STAIR) starting at 90 min after meal accelerates the decrease in blood glucose concentrations in middle-aged sedentary men with impaired glucose tolerance, although STAIR is easy to perform and keeps the exercise intensity at a moderate level.

[Recommendation of using a registering type GPS and a heart rate monitor for walking instructions in the elderly].

OBJECTIVE: The efficacy of exercise for health promotion depends on the protocol. We examined the possibility of determining the characteristics of walking (route, speed and work intensity) with a registering type GPS and a heart rate monitor. We also demonstrated the effects of giving a walking regimen utilizing the data on characteristics of walking. METHODS: Route, speed, and heart rate during the walking of 24 elderly habitual walkers were estimated with a memory-type GPS apparatus and a heart rate monitor, respectively. The elderly were instructed to modify the route and/or speed of walking according to the data. RESULTS: 1) The walking speeds for male and female subjects increased from 91.8 +/- 12.8 m/min to 97.3 +/- 12.2 m/min and 81.4 +/- 9.7 m/min to 85.6 +/- 7.0 m/min, respectively (P<0.05). 2) The average work intensity estimated by% HRR during the walking increased from 37.0 +/- 10.5% to 48.6 +/- 8.9% and 34.9 +/- 13.4% to 47.7 +/- 8.8%, respectively (P<0.01). CONCLUSIONS: Utilization of a GPS apparatus and a heart rate monitor is effective in determining characteristics of walking and facilitates giving effective instructions for health promotion to the elderly with a habit of walking.

Effect of cycling experience and pedal cadence on the near-infrared spectroscopy parameters.

PURPOSE: Previously we demonstrated that the method to reorder near-infrared spectroscopy (NIRS) parameters against crank angle could serve as a useful measure in providing circulatory dynamics and metabolic changes in a working muscle during pedaling exercise. To examine further applicability of this method, we investigated the effects of cycling experience and pedal cadence on the NIRS parameters. METHODS: Noncyclists (NON), triathletes (TRI), and cyclists (CYC) performed pedaling exercises at a work intensity of 75% VO2max while changing pedal cadence (50, 75, 85, and 95 rpm). Physiological and biomechanical responses and NIRS parameters were measured. RESULTS: NIRS measurements determined with the reordered NIRS change demonstrated significant differences depending on the factors. The bottom peak of reordered NIRS changes in muscle blood volume and oxygenation level shifted upward with an increase in pedal cadence in NON but remained unchanged in CYC. The reordered NIRS change demonstrated a temporary increase at the crank angle corresponding to the relaxation phase of the working muscle. This temporary increase was observed even in the highest pedal cadence in CYC. The difference in levels between the peak of the temporary increase and the bottom peak of reordered NIRS change (LPB-diff) for CYC at 85 rpm was significantly larger than that for NON. The results with NIRS parameters corresponded to changes in pedal force and myoelectric activity during pedal thrust. CONCLUSIONS: The bottom peak level of the reordered NIRS changes and LPB-diff determined for blood volume are available to detect noninvasively the differences in circulatory dynamics and metabolic change during pedaling exercises performed at different pedal cadences and also to estimate the difference of physiological and technical developments for endurance cycling in athletes.

H2O2 activates ryanodine receptor but has little effect on recovery of releasable Ca2+ content after fatigue.

We studied whether hydrogen peroxide (H(2)O(2)) at

Changes in blood volume and oxygenation level in a working muscle during a crank cycle.

PURPOSE: This study examined circulatory and metabolic changes in a working muscle during a crank cycle in a pedaling exercise with near-infrared spectroscopy (NIRS). METHODS: NIRS measurements sampled under stable metabolic and cadence conditions during incremental pedaling exercise were reordered according to the crank angles whose signals were obtained in eight male subjects. RESULTS: The reordered changes in muscle blood volume during a crank cycle demonstrated a pattern change that corresponded to changes in pedal force and electrical muscle activity for pedal thrust. The top and bottom peaks for muscle blood volume change at work intensities of 180 W and 220 W always preceded (88 +/- 32 and 92 +/- 23 ms, respectively) those for muscle oxygenation changes. Significant differences in the level of NIRS parameters (muscle blood volume and oxygenation level) among work intensities were noted with a common shape in curve changes related to pedal force. In addition, a temporary increase in muscle blood volume following a pedal thrust was detected at work intensities higher than moderate. This temporary increase in muscle blood volume might reflect muscle blood flow restriction caused by pedal thrusts. CONCLUSION: The results suggest that circulatory and metabolic conditions of a working muscle can be easily affected during pedaling exercise by work intensity. The present method, reordering of NIRS parameters against crank angle, serves as a useful measure in providing additional findings of circulatory dynamics and metabolic changes in a working muscle during pedaling exercise.