Blood biochemical indices of iron status were measured in venous blood from 20 runners and 6 control subjects. All subjects were.male, ages 20 to 40 years, and stable with regard to body weight and degree of physical activity. Dietary analysis was undertaken using a 7-day weighed food intake. There was no evidence of iron deficiency: hemoglobin concentrations and serum femtin levels were within the normal population range for all individuals. However, serum ferritin was negatively correlated with the amount of training. Daily iron intake appeared to be adequate; iron intake was correlated with protein intake but not related to training or energy intake. Serum ferritin, an indicator of iron status, was significantly correlated with vitamin C intake but not iron intake. Serum transferrin concentration was higher in the group of athletes undertaking a high weekly training load compared with the control subjects, suggesting an alteration in iron metabolism although there was no evidence of increased erythropoiesis. The biological significance of this is unclear.
John D. Robertson, Ronald J. Maughan, Ann C. Milne and Ronald J.L. Davidson
Joel T. Fuller, Clint R. Bellenger, Dominic Thewlis, John Arnold, Rebecca L. Thomson, Margarita D. Tsiros, Eileen Y. Robertson and Jonathan D. Buckley
Stride-to-stride fluctuations in running-stride interval display long-range correlations that break down in the presence of fatigue accumulated during an exhaustive run. The purpose of the study was to investigate whether long-range correlations in running-stride interval were reduced by fatigue accumulated during prolonged exposure to a high training load (functional overreaching) and were associated with decrements in performance caused by functional overreaching.
Ten trained male runners completed 7 d of light training (LT7), 14 d of heavy training (HT14) designed to induce a state of functional overreaching, and 10 d of light training (LT10) in a fixed order. Running-stride intervals and 5-km time-trial (5TT) performance were assessed after each training phase. The strength of long-range correlations in running-stride interval was assessed at 3 speeds (8, 10.5, and 13 km/h) using detrended fluctuation analysis.
Relative to performance post-LT7, time to complete the 5TT was increased after HT14 (+18 s; P < .05) and decreased after LT10 (–20 s; P = .03), but stride-interval long-range correlations remained unchanged at HT14 and LT10 (P > .50). Changes in stride-interval long-range correlations measured at a 10.5-km/h running speed were negatively associated with changes in 5TT performance (r –.46; P = .03).
Runners who were most affected by the prolonged exposure to high training load (as evidenced by greater reductions in 5TT performance) experienced the greatest reductions in stride-interval long-range correlations. Measurement of stride-interval long-range correlations may be useful for monitoring the effect of high training loads on athlete performance.