What are the Physiological Benefits of Increased Daily Number of Steps in Middle-Aged Women?

BACKGROUND: Physical activity plays an important role in the prevention of cardio-metabolic diseases. The present study evaluated the effect of habitual physical activity on body composition, peak oxygen consumption, cardiac and metabolic function. METHODS: This was a retrospective study. Data was collected between February 2014 and November 2015. Thirty-six healthy women (age 50±16 years) were stratified according to daily number of steps into low- (<7500 steps/day, n=17) or high-active group (>12500 steps/day, n=19). All participants underwent body composition assessment, oral glucose tolerance test and non-invasive gas-exchange and haemodynamic (bioreactance) measurements at rest and in response to maximal graded cardiopulmonary exercise test. RESULTS: The high active group averaged 16280±3205 steps/day and the low active group averaged 6285±943 steps/day (difference p=0.00). High-active women (vs. low active) demonstrated significantly lower body weight (62.1±12.3 vs. 71.2±9.1 kg, p=0.02), body fat (27.2±9.1 vs 37.7±6.4 %, p=0.00), but increased lean body mass (72.8±9.1 vs. 62.3±6.4 %, p=0.00). Peak oxygen consumption was significantly higher in high- versus low active women (2.0±0.5 vs. 1.5±0.2 l/min, p=0.00). There were no significant differences between the groups in fasting- and 2-hour glucose levels (4.9±0.6 vs. 4.8±0.5, p=0.45 and 4.8±1.3 vs. 5.5±1.4 mmol/L, p=0.16) haemodynamic measures of cardiac function including cardiac power output, cardiac output, stroke volume and arterial blood pressure at rest and in response to exercise stress test (p>0.05). CONCLUSIONS: Increased levels of habitual physical activity improve body composition and peak oxygen consumption but appears to have limited effect cardio-metabolic function in middle-aged women.

Reproducibility of Inert Gas Rebreathing Method to Estimate Cardiac Output at Rest and During Cardiopulmonary Exercise Stress Testing.

The present study evaluated reproducibility of the inert gas rebreathing method to estimate cardiac output at rest and during cardiopulmonary exercise testing. Thirteen healthy subjects (10 males, 3 females, ages 23-32 years) performed maximal graded cardiopulmonary exercise stress test using a cycle ergometer on 2 occasions (Test 1 and Test 2). Participants cycled at 30-watts/3-min increments until peak exercise. Hemodynamic variables were assessed at rest and during different exercise intensities (i. e., 60, 120, 150, 180 watts) using an inert gas rebreathing technique. Cardiac output and stroke volume were not significantly different between the 2 tests at rest 7.4 (1.6) vs. 7.1 (1.2) liters min-1, p=0.54; 114 (28) vs. 108 (15) ml beat-1, p=0.63) and all stages of exercise. There was a significant positive relationship between Test 1 and Test 2 cardiac outputs when data obtained at rest and during exercise were combined (r=0.95, p<0.01 with coefficient of variation of 6.0%), at rest (r=0.90, p<0.01 with coefficient of variation of 5.1%), and during exercise (r=0.89, p<0.01 with coefficient of variation 3.3%). The mean difference and upper and lower limits of agreement between repeated measures of cardiac output at rest and peak exercise were 0.4 (-1.1 to 1.8) liter min-1 and 0.5 (-2.3 to 3.3) liter min-1, respectively. The inert gas rebreathing method demonstrates an acceptable level of test-retest reproducibility for estimating cardiac output at rest and during cardiopulmonary exercise testing at higher metabolic demands.

Cardiac function is not associated with glucose control in older women.

The present study evaluated the effect of age on glucose tolerance and cardiac function and assessed the relationship between metabolic control and cardiac function and performance. Thirty-four healthy women aged 40 to 81 years were divided into two age groups: younger (≤50 years of age, N = 19) and older (≥60 years of age, N = 15). Participants performed an oral glucose tolerance test and a graded cardiopulmonary exercise test with non-invasive haemodynamic measurements. Compared to younger, older women demonstrated significantly higher 2-hour glucose (4.67 ±â€¯1.01 vs 6.08 ±â€¯1.54 mmol/l, P < 0.01), but lower peak exercise O2 consumption (1.96 ±â€¯0.44 vs 1.38 ±â€¯0.26 l/min, P < 0.01) and cardiac power output (4.06 ±â€¯0.76 vs 3.35 ±â€¯0.73 W, P = 0.01). When data from all study participants were combined, there was a significant negative relationship between 2-hour glucose and peak cardiac power (r = -0.39, P = 0.02), and peak O2 consumption (r = -0.40, P = 0.02). The strength of these relationships was affected by age, with moderate negative relationship identified between 2-hour glucose and peak cardiac power output in younger compared to older participants (r = -0.38, P = 0.11 vs. r = -0.09, P = 0.75). Metabolic control and cardiac function decline with age. The lack of relationship between glucose control and cardiac power may suggest that metabolic control does not influence cardiac function and performance in older women.