Women with exercise associated amenorrhea display a disturbance in basal and exercise levels of reproductive, anti-reproductive and stress hormones. Co-incident with chronic exercise are other factors, which alone, also affect the menstrual cycle. Therefore, amenorrheic runners (AR), regularly menstruating runners (RMR) and regularly menstruating sedentary controls (RMSC) were compared for plasma progesterone levels, plasma lipid levels, menstrual cycle characteristics, physical characteristics and nutritional adequacy to determine if the difference in menstrual status could be explained, and to determine whether exercise alone could be attributed as the cause of menstrual cycle disturbances.Plasma progesterone levels were significantly lower in the AR group (. 28 + .02 ng/ml) than in the RMR group (.41 + .06 ng/ml) and the RMSC group (.49 + .06 ng/ml) in the follicular phase. Regularly menstruating runners demonstrated lower plasma progesterone levels in the luteal phase (9.76 + 1.05 ng/ml) than RMSC subjects (10.24 + 2.21 ng/ml). Regularly menstruating runners had a significantly shorter luteal phase length relative to their cycle length (.35 + .01) than RMSC subjects (.46 + .01). Mean age, incidence of parity, age of menarche, height, weight, body composition, max V02 and number of miles run per week did not differ between the RMR and AR subjects. Amenorrheic runners took in significantly less fat, red meat, phosphorous and total calories than the RMR subjects. Serum LDL-C was significantly higher in the AR subjects (89.2 + 9.7 mg/dl) than in the RMR subjects in both the luteal (67.8+ 3.4 mg/dl) and follicular (66.8+ 5.6 mg/dl) phases. Serum HDL-C was significantly higher in the RMR subjects in both the luteal (62.9+ 4.1 mg/dl) and follicular (59.2+ 2.9 mg/dl) phase, and in the AR subjects (63.9+ 4.2 mg/dl), than in the RMSC subjects in the luteal (49.2+ 5.9 mg/dl) and follicular (47.2+ 2.4 mg/dl) phase. Serum VLDL-C did not differ between any groups.This investigation demonstrates that hormonal and lipid level alterations with exercise are significantly different in the amenorrheic runner. However, regularly menstruating runners display alterations which may represent and intermediate or potential phase of menstrual cycle disturbances. The nutritional inadequacy or energy imbalance separates amenorrheic runners from regularly menstruating runners. Thus, it appears that exercise alone is not enough to cause the hormonal disturbances that trigger amenorrhea, and, that exercise associated amenorrhea is not unlike other amenorrheas of hypothalamic origin.

No description available.

The purpose of this study was to investigate the effect of prolonged exercise on running economy. Fourteen male long distance runners performed two 90 minute runs on an outdoor 400m track at velocities equal to 65 and 80% of VO$ sb2$max. Prior to and following each 90 minute run, running economy (RE) was measured as the steady-state VO$ sb2$ during treadmill runs at speeds of 188 and 228 m/min. During the 90-min run at 65% of VO$ sb2$max, the mean weight loss was 1.3 kg. The HR was 143 bpm between minutes 5-10 and increased to 150 bpm between minutes 85-90. During the 90-min run at 80% of VO$ sb2$max, the mean weight loss was 1.4 kg. The HR was 161 bpm between minutes 5-10 and increased to 165 bpm between minutes 85-90. When the post RE test was conducted following each 90-min run, there was a significant increase in VO$ sb2$ expressed in both l/min and ml/kg$ cdot$min (a decrease in running economy). The increase in oxygen cost of running following the 90-min run at 80% of VO$ sb2$max was greater than that following the run at 65% of VO$ sb2$max.

Seven highly trained male collegiate distance runners were studied throughout a competitive cross-country season. Common laboratory and field measures were used to assess physiological adaptation and performance capacity. The subjects were tested pre-, mid-, and post-season for maximal oxygen consumption (VO2max), running economy (RE), heart rate at 268 m-min…1 (HR268), fractional utilization of the aerobic capacity (%VO2max), fraction utilization of the maximal heart rate (%HRmax), ventilatory threshold (VT), and time to exhaustion (TTE). Prior to each scheduled competition submaximal hear rate (HR) and submaximal blood lactate accumulation (bLa) were determined from a one-mile run on an indoor track. Five subjects ran at 5 min 30 sec per mile pace and two ran at a 6 min per mile pace (mean intensity = 83.14 + 4.44% VO2max). VO2max, RE, % VO2max, %HRmax and TTE all significantly improved over the season (p < 0.05). VT and HR268 remained unchanged. % VO2max and %HRmax exhibited the highest correlations to performance within a given competition (range r = .525 to .722 and .571 to .844, respectively). HR and bLa did not change during the season. These results suggest: 1) % VO2max and %HRmax are the best predictors of cross-country running performance among the variables measured whereas 2) field trials employing single HR and single bLa measurements are not indicators of endurance running performance in highly trained distance runners. / Human Performance Laboratory

Despite similar rates of energy expenditure during training, competitive swimmers have been shown to store significantly greater amounts of body fat than competitive runners. In an attempt to explain these discrepancies, male collegiate swimmers (n=8) and runners (n=8) were monitored during 45 min of swimming and running, respectively (75% V02 max), and during two hours of recovery. In addition, a group of male competitive triathletes (n=6) were similarly monitored during and after both swimming and running exercise.Blood samples were obtained after 15 min rest prior to exercise and at 0, 15, 30, 60 and 120 min of recovery and were analyzed for glucose, lactate, glycerol, free fatty acids, insulin, glucagons, norepinephrine (NE) and epinephrine (E). Respiratory gases were collected at 15 min intervals during exercise and at 15, 30, 45, 60, 90 and 120 min of recovery. Heart rate and mean body temperature were recorded at 10 min intervals throughout recovery. There were no differences in post-exercise oxygen consumption or heart rate while the RER suggested increased fat oxidation after exercise for the swimmers and the swimming triathletes. The mean body temperature and mean skin temperatures were significantly lower throughout 120 min of recovery for the swimmers compared to the runners. The triathletes demonstrated a similar tendency but these differences were not significant. The serum glucose levels were significantly greater (P<0.05) immediately post-exercise for the runners compared to the swimmers (6.71 +0.29 and 4.97 +0.19 mmol•1-1, respectively). Blood glucose values were also significantly greater immediately post-run for the triathletes (6.40 +0.26 and 4.87 ±0.18 mmol-l-1 for running and swimming, respectively). Blood glucose values remained elevated for runners and the running triathletes up to 30 min of recovery. Free fatty acids were similar after the run and the swim, but glycerols were increased immediately after running in the runners (P<0.05) and the triathletes (P<0.05). Differences in blood glucose levels or fat release were not explained by differences in NE, E or cortisol. The glucagon-to-insulin (G:I) ratio was significantly increased after exercise in the swimmers and the swimming triathletes. This, combined with a reduced RER after the swimming trials, suggests that the reduced glucose levels were due to reduced hepatic glycogen stores. The results of this study suggest that there were differences in substrate utilization during running and swimming exercise of the same intensity. These differences were not explained by NE, E or cortisol; however, the increased G:T ratio suggests increased carbohydrate use during exercise in the swimmers. Finally, body fat differences between runners and swimmers were not explained by differences in post-exercise energy expenditure or fat oxidation.

Ten trained male track athletes (VO2max = 64.7 ml&middot;kg&middot;min -1) performed three workouts (conditions) with repeated 400-m runs. The intensity and number of repetitions varied among conditions. Condition 1 consisted of two all-out 400-m runs. Condition 2 was 4 x 400-m runs with the first three reps performed 4 s slower than condition 1 and the 4 th rep was all-out. Condition 3 consisted of 8 x 400-m runs with the first seven reps performed 8 s slower than condition 1 and the 8th rep was all-out. Dependent variables were HR, blood lactate and run time for the final rep in each condition. Peak HRs for the last run were 201, 194, 189 beats&middot;min-1 for conditions 1, 2 & 3 respectively, and were not significantly different. Blood lactate values measured 4 min after the last run were 16.6, 17.8 and 17.1 mmol&middot;L -1 in conditions 1, 2 and 3 respectively, and were not significantly different. Run times for conditions 1 (55.2 s), 2 (56.9 s) and 3 (61.5 s) were significantly different (P < 0.05). The decline in performance was greatest in condition 3. The three conditions challenged the anaerobic system with similar peak values for lactate and heart rate during the final run.

This study investigated the influence of human morphology upon selected physiological, biomechanical and psychological responses to horizontal locomotion. In so doing, it was possible to evaluate the effectiveness with which morphology-normalised speeds of walking and running reduced the between-subject variability that is inherent in human locomotor responses. Twenty caucasian males were divided into two groups on the basis of stature - ten subjects in each of a "short" category (<170cm) and a "tall" category (>185cm). All subjects were habituated to treadmill locomotion prior to exposure to three walking treatments (0.83, 1.39 and 1.94m.s⁻¹) and three running treatments (2.50, 3.06 and 3.61m.s⁻¹). During each of these five-minute locomotor conditions, energetic (V02), kinematic (cadence and stride length) and psychophysical (central and local RPE) data were captured. From these data, lines of best fit were calculated for each subject, allowing for a prediction of the abovementioned locomotor variables from known absolute rates of progression. Using suitable regression equations, subject responses to morphology-normalised speeds of walking and running were effectively extrapolated. When the rate of progression was expressed in absolute terms (m.s⁻¹), significant differences (P <0.05) were found between the stature-related groups with respect to both energetic and kinematic locomotor responses. Such differences were successfully eliminated when use was made of locomotor speeds relativised on the basis of morphology. This study concludes that the use of appropriately prescribed morphology-normalised rates of progression are effective in reducing the variability in locomotor responses between subjects differing significantly in stature.

[Conclusions] l) The two forms of human locomotion, walking and running, are distinctly different and in evaluating these gait patterns consideration must be given to this fact. 2) The impression created by the energy cost curves, that there is a single locomotor interface for both walking and running is a false one . There are two distinctly different locomotor interfaces, the walk-to-run interface and the run-to-walk interface. The former appears to correspond with the "metabolic intersection point" and therefore has some metabolic significance. The latter appears to be merely an "overshoot" of the walk-to-run interface and presently has no apparent metabolic significance. 3) Because the walk-to-run interface speed corresponds with the intersection point of the energy cost curves, physiological responses to walking and running at this speed do not differ significantly. However, cadence and stride length patterns for these two locomotor patterns are distinctly different at this point. 4) The identification of single physiological or kinematic factors during perceptions of exertion in any given situation is an extremely difficult if not impossible task. Perceived exertion should therefore be considered a multi-factorial concept and should be evaluated as such. 5) The use of relative speed as a technique for reducing inter-subject variability in physiological and kinematic factors is worthless unless diverse ranges in morphological linearity are a characteristic of one's subject pool

No description available.

No description available.