Moderate intensity exercise training improves cardiorespiratory fitness in women.

Among women, there is an increased prevalence of sedentary lifestyle and less participation in physical activity at levels recommended by the Surgeon General. As a result, women have been identified as a target group in public health initiatives to increase physical activity. The health-related benefits of habitual, moderate intensity physical activity are well documented in the epidemiological literature, but less is known about the effect of such physical activity on cardiorespiratory fitness. Our hypothesis was that moderate and vigorous exercise training regimens of similar estimated energy expenditure would result in similar changes in cardiorespiratory fitness. Eighteen sedentary premenopausal women with the following baseline characteristics [x +/- SE]: maximal oxygen consumption (Vo2max) = 29.5+/-1.5 ml x kg(-1) x min(-1); age = 33+/-1 years; height = 162.6+/-0.9 cm; mass = 62.7+/-2.3 kg, were randomly assigned to either vigorous (HI, 80% Vo2max, n = 10) or moderate intensity (MOD, 40% Vo2max, n = 8) cycle ergometer training groups. Exercise training was conducted 3-4 (3.37+/-0.05) days/week for 12 weeks in a supervised and progressive manner, with estimated exercise energy expenditure equated across both training groups. Vo2max and time to exhaustion increased significantly in both groups (p<0.05), with no difference between groups. Both groups had lower (p<0.05) posttraining submaximal heart rates (HR), respiratory exchange ratios (RER), and ratings of perceived exertion (RPE) during graded exercise testing, with no significant differences between the groups in posttraining values. Women participating in moderate intensity exercise training as recommended in basic public health guidelines demonstrate an increase in cardiorespiratory fitness similar to that elicited by vigorous training.

Exercise training and intensity does not alter vascular volume responses in women.

PURPOSE: The effect of endurance training on vascular volumes in females has received little research attention. Further, the effect of exercise training intensity on vascular volumes is unknown. Therefore, we investigated the hypothesis that greater hematologic changes would be induced in women by higher exercise intensity during endurance training. METHODS: There were 26 healthy, sedentary adult females with the following characteristics (mean +/- SD): maximal oxygen consumption (VO2max) = 30.0+/-6.6 ml x kg(-1) x min(-1); age = 32+/-5 yr; body mass index (BMI) = 23.7+/-3.6 kg x m(-2)) who were randomly assigned to control (CON, n = 8); high intensity (HI, 80% of VO2max, n = 10), or low intensity (LO, 40% of VO2max, n = 8) cycle ergometer training groups. Training, conducted 3-5 (3.37+/-0.05) d x wk(-1) for 12 wk, was supervised. Estimated exercise energy expenditure was equated across training groups, progressing from 150-375 kcal per session (mean +/- SE across training weeks = 298+/-0.34 and 297+/-0.37 kcal per session for HI and LO, respectively). Plasma volume (PV, T-1824 dilution); calculated total blood (TBV) and red cell volumes (RCV); calculated total hemoglobin (THb); erythropoietin concentration ([Epo]) and selected hematologic variables were measured at baseline and weeks 2, 4, 8 and 12 of training. RESULTS: The observed relative (percent) changes in PV, TBV, RCV and THb from pre-training baseline values were not statistically significant. Decreases (p < 0.05) in hematocrit (Hct), hemoglobin ([Hb]) and RBC count were observed in both training groups. Mean corpuscular Hb (MCH) and Hb concentration (MCHC) increased (p < 0.05) during training. [Epo] was decreased at week 2 compared with baseline (p < 0.03), but was similar to baseline at weeks 4, 8 and 12. CONCLUSIONS: Within the limits of this study, endurance training did not increase PV, TBV, RCV and THb in previously sedentary females regardless of the intensity of training.

Twelve weeks of endurance exercise training does not affect iron status measures in women.

OBJECTIVE: This study examined the effects of 12 weeks of endurance exercise training on iron status measures in previously inactive women and compared the effects of weight-bearing endurance exercise training and non-weight-bearing endurance exercise on iron status measures. DESIGN: Randomized, experimental study. SUBJECTS: Thirty-one healthy, inactive women (aged 23 to 43 years) with apparently normal iron stores (serum ferritin concentration > or = 20 micrograms/L) were recruited from the local area by newspaper advertisements and campus mailings. Twenty-one subjects completed the study (mean +/- standard deviation for age = 32 +/- 5 years, for body mass index = 23.1 +/- 4.9, and for maximum oxygen consumption [VO2max] = 33.8 +/- 6.3 mL/kg per minute). INTERVENTION: Subjects were randomly assigned to one of three groups: an inactive control group, a walking/running group, or a cycling group. Subjects in the two exercise groups trained three to four times per week at 80% VO2max for 12 weeks. Exercise training sessions were monitored and energy expenditure increased from 150 kcal per session (week 1) to 375 kcal per session (weeks 9 to 12). Subjects in the inactive control group were instructed to maintain their normal activity patterns for the duration of the study. All subjects were instructed to maintain their normal dietary habits. MAIN OUTCOME MEASURES: Serum ferritin concentration, serum iron concentration, percentage saturation of transferrin, total iron-binding capacity, serum haptoglobin concentration, and other selected hematologic variables were measured at baseline and at weeks 2, 4, 8, and 12. STATISTICAL ANALYSES: Repeated measures analysis of variance was used to examine group x time interactions in changes in iron status measures. Statistical significance was reached at P < .05. RESULTS: Analysis of variance indicated that serum ferritin concentration did not change significantly (P = .59) during the 12 weeks in the walking/running group (mean +/- standard deviation from 41.28 +/- 14.22 to 27.41 +/- 9.74 micrograms/L) or the cycling group (from 65.81 +/- 37.62 to 41.06 +/- 26.38 micrograms/L) compared with the control group (from 47.55 +/- 15.87 to 31.56 +/- 10.57 micrograms/L). Values for serum iron, total iron-binding capacity, percentage saturation of transferrin, and haptoglobin also did not change significantly (P > .30) in the walking/running or cycling groups compared with the control group. APPLICATIONS/CONCLUSIONS: Results of this study suggest that participation in 12 weeks of moderate-intensity endurance exercise training (walking/running or cycling) is not associated with negative effects on selected measures of iron status in healthy, previously untrained women with normal iron stores (serum ferritin > or = 20 micrograms/L).

Effects of exercise mode on hematologic adaptations to endurance training in adult females.

BACKGROUND: The subjects were 26 healthy, sedentary adult females with the following characteristics: maximal oxygen consumption (VO2max) = 32.0 +/- 7.2 ml.kg-1.min-1; age = 32 +/- 5 yr; body mass index (BMI) = 23.2 +/- 3.4 kg.m-2 who were randomly assigned to control (CON; N = 8); treadmill training (TM; N = 8); or cycle ergometer training (CY; N = 10) to test the hypothesis that hematologic adaptations to endurance exercise training are specific to mode of exercise. METHODS: Training, conducted 3-5 (3.4 +/- 0.06) d.week-1 at 80% of mode specific VO2max for 12 weeks, was supervised and progressive, with estimated exercise energy expenditure equated across training groups. Plasma volume (PV, T-1824 dilution); calculated total blood (THb) and red cell volumes (RCV); calculated total hemoglobin (THb) and other hematologic variables were measured at baseline and weeks 2, 4, 8 and 12 of training. RESULTS: Across 12 weeks of training, PV was decreased (95% of baseline) in the TM group but increased (106% of baseline) in the CY group (p = 0.06). Similar trends were observed for RCV (p = 0.15) and TBV (p = 0.08). These results are in contrast to reported changes in PV, TBV and RCV in males following training. Hemodilution was observed in both training groups, reflected by decreases (p < 0.05) in hematocrit (Hct), hemoglobin (Hb) and RC count. Mean corpuscular Hb (MCH) and Hb content (MCHC) increased (p < 0.05) with training. These changes, as well as trend toward increased (p = 0.08) mean corpuscular volume (MCV), suggested the probable presence of a RC population with a lower mean age and decreased oxyhemoglobin affinity. The possibility of Type II error cannot be discounted in these trends, which suggest that PV, TBV and RCV may be affected by mode of endurance exercise in females.

Effect of iron supplementation on endurance capacity in iron-depleted female runners.

The purpose of this investigation was to examine the effects of oral iron supplementation on endurance performance in initially iron-depleted, nonanemic female distance runners. Eighteen iron-depleted (serum ferritin less than 20 ng.ml-1, hemoglobin greater than or equal to 12 g.dl-1) women (22-39 yr) performed a VO2max test and an endurance run to exhaustion. Subjects were pair-matched on the basis of endurance time and then randomly assigned to an iron supplement or a placebo group. Following supplementation, the iron group had a significantly higher (P = 0.03) mean serum ferritin concentration (23.4 vs 15.7 ng.ml-1) and lower (P = 0.04) mean total iron-binding capacity than the placebo group. Both groups increased their time to exhaustion (25.5% and 22.2% for the iron and placebo groups, respectively) but were not significantly different (P = 0.72) from each other. There were also no differences (P greater than 0.05) between the groups with respect to lactate concentrations and physiological measures taken during the two exercise tests. The results of this study suggest that 8 wk of oral iron supplementation improves iron status in iron-depleted female distance runners, but does not enhance endurance capacity.