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

Abstract

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).