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Mooses, M, Haile, DW, Ojiambo, R, Sang, M, Mooses, K, Lane, AR, and Hackney, AC. Shorter ground contact time and better running economy: evidence from female Kenyan runners. J Strength Cond Res 35(2): 481-486, 2021-Previously, it has been concluded that the improvement in running economy (RE) might be considered as a key to the continued improvement in performance when no further increase in V̇o2max is observed. To date, RE has been extensively studied among male East African distance runners. By contrast, there is a paucity of data on the RE of female East African runners. A total of 10 female Kenyan runners performed 3 × 1,600-m steady-state run trials on a flat outdoor clay track (400-m lap) at the intensities that corresponded to their everyday training intensities for easy, moderate, and fast running. Running economy together with gait characteristics was determined. Subjects showed moderate to very good RE at the first (202 ± 26 ml·kg-1·km-1) and second (188 ± 12 ml·kg-1·km-1) run trials, respectively. Correlation analysis revealed significant relationship between ground contact time (GCT) and RE at the second run (r = 0.782; p = 0.022), which represented the intensity of anaerobic threshold. This study is the first to report the RE and gait characteristics of East African female athletes measured under everyday training settings. We provided the evidence that GCT is associated with the superior RE of the female Kenyan runners.

INTRODUCTION An in-depth understanding of the healthy cartilage response to activities of daily living is needed to better understand the complex relationship between cartilage health and loading. The purpose was to assess the role of loading on the acute serum cartilage oligomeric matrix protein (COMP) response in recreationally active individuals. METHODS Forty individuals without previous lower extremity injury participated in this repeated-measures study in which each participant completed all conditions during independent data collection sessions separated by at least 1 wk. An antecubital blood draw was performed before and after walking, drop-landing, and control (i.e., sitting) conditions. Commercially available enzyme-linked immunosorbent assays measured COMP concentration. The acute COMP response was quantified as the percent change of COMP concentration from before to after each condition. A one-way, repeated-measures ANOVA compared the acute COMP response between conditions. Post hoc Pearson product-moment correlation and chi-square analysis determined the relationship between the walking and drop-landing acute COMP response within individuals. RESULTS Acute COMP response was greater after walking (+4.2, P = 0.008) and drop landing (+4.6%, P = 0.002) compared with control (-2.3%), but did not differ between the walking and drop-landing conditions (P = 0.596). The magnitudes of the acute COMP response during walking and drop landing were correlated (r = 0.56, P < 0.001). However, the direction (i.e., either increase or decrease) of COMP was not the same after the walking and drop-landing conditions (χ1 = 0.870, P = 0.351). CONCLUSIONS Walking and drop landing produced a greater acute COMP response when compared with a control condition in healthy individuals, but the acute COMP response was similar between the two physical activity conditions, although the conditions differed in magnitude and frequency of loading.

OBJECTIVE: To determine the effect of oral contraceptives (OC) on hamstring neuromechanics and lower extremity stiffness across the menstrual cycle (MC). DESIGN: Causal comparative. SETTING: Research laboratory. PARTICIPANTS: Thirty healthy normally menstruating female volunteers who were using OC (OC group n = 15) or not (non-OC group n = 15). ASSESSMENT OF RISK FACTORS: Stiffness and hamstring neuromechanics were assessed at 2 points of the MC corresponding to low (menses) and high (ovulation) hormone concentrations. Menses testing took place 3 to 5 days after the onset of menses (or pills 3-5 for the OC group). Ovulation test session occurred 2 to 4 days after ovulation identified using a commercial ovulation kit (or pills 15-17 in the OC group). MAIN OUTCOME MEASURES: Lower extremity stiffness and hamstring neuromechanics [stiffness electromechanical delay rate of force production (RFP) time to 50% peak force (T50%)] and blood plasma concentrations of estradiol-beta-17 free testosterone and progesterone. RESULTS: Estradiol-beta-17 free testosterone and progesterone increased at ovulation in the non-OC group and remained constant in the OC group. No changes were observed across the MC or between the groups in other variables (P > 0.05). CONCLUSIONS: Although previous literature suggests a prophylactic effect of OC use with respect to musculoskeletal injury risk our results indicate that OC use does not affect muscle properties in manners thought to reduce ACL injury risk.

To examine the effects of prolonged systemic administration of diclofenac sodium (Voltaren), a nonsteroidal anti-inflammatory drug, on objective indices of exercise-induced muscle damage in humans.Fifty-four volunteers (mean age, 26.4 yr; range, 18-35) participated in this randomized double-blind, placebo-controlled trial. To achieve steady-state tissue levels, either placebo or diclofenac was orally administered two times a day for 27 consecutive days. A strenuous 20-min stepping exercise program, about which the subjects were unfamiliar, was conducted on day 15. Creatine kinase (CK) activities were measured immediately before the exercise session and on days 16, 18, and 27. Vastus lateralis muscle samples were obtained immediately before exercise and on day 27 for subsequent histological characterization of muscle inflammation.The preexercise muscle samples revealed no difference in muscle damage between the two groups. However, the postexercise muscle samples showed that the diclofenac-treated group demonstrated less muscle tissue damage than placebo-treated subjects (P = 0.002). The administration of diclofenac also resulted in a significant lowering of post-/pre-exercise CK ratios on days 18 (P = 0.03) and 27 (P = 0.02) compared with the placebo group, an indirect finding that supports the possibility of diclofenac reducing exercise-induced muscle damage.These findings demonstrate preadministration of diclofenac (in accordance with tissue half-life pharmacokinetics) significantly reduces quantitative indices of exercise-induced skeletal muscle damage in human muscle.

The Heart rate variability (HRV) power spectrum is a non-invasive index of parasympathetic and sympathetic branches of the autonomic nervous system (ANS). Sex hormone oscillations may affect autonomic nervous system function; however, no systemic difference in HRV across the menstrual cycle has been shown. The purpose of this study is to test the hypothesis that there are changes in HRV spectral power components across the menstrual cycle. Method: Eleven women (24.4±3.6 years) volunteered for this experiment. Menstrual cycle phase was determined via basal body temperature mapping. Participants were tested once in each cycle phase. A 3 lead ECG was sampled at 1000 Hz. A piezoelectric force transducer, placed around the chest, recorded breathing rate. After 20 minutes of quiet seated rest, 5 minutes of data was collected in the upright seated position. Power spectral density analysis was performed on the R-R interval variations by fast Fourier transformation. The spectrum was divided into low (0.04-0.15, Hz) and high (0.15-0.40 Hz) frequency components. In order to attain data normality, the components were transformed with a natural logarithm. A repeated measures ANCOVA was used with a piece-wise covariate function for breathing rates higher and lower than 10 breaths per minute. Results: A significant decrease in total power spectrum was observed at the ovulatory phase (P=0.04) compared to the early follicular, late follicular and mid luteal phases. Furthermore, high-frequency oscillations were lower (P=0.04) in the ovulatory phase compared to late follicular phase. There were no changes observed (P>0.05) in the low frequency power spectrum across the menstrual cycle. Conclusions: The decrease in the high-frequency components of the HRV power spectrum during the ovulatory phase indicates a decrease in parasympathetic regulation of the heart. The ovulatory phase is characterized by an elevated level of progesterone, follicle stimulating and luteinizing hormones, and a moderate level of estradiol. Thus, the changes in these hormones during ovulation appear to affect ANS function.

This study examined the plasma glucose, free fatty acids (NEFA), lactate, triglyceride, cortisol, and insulin responses of pregnant women (22-28 wk) to a 40-min aerobic dance program and 40-min treadmill walking at similar heart rate intensities. The heart rates during exercise averaged 135 +/- 5 bt.min-1 for both trials. Immediate post-exercise plasma glucose levels were lower than resting levels for both exercise trials (P < 0.05), and remained below resting levels 20 min after exercise. Plasma triglycerides and NEFA were increased immediately post-exercise (P < 0.05), and returned toward rest 20 min after exercise. The NEFA responses at the end of the walking trials were significantly greater than at the end of the aerobic dance trials (P < 0.05). For both trials, immediate post-exercise plasma insulin levels were below resting levels (P < 0.05) and remained attenuated 20 min post-exercise. Plasma cortisol concentrations were unchanged throughout the aerobic dance trial. However, a mean increase of 105 nmol.l-1 immediately post-exercise was evident during the walking trials (P < 0.05). The results suggest that 40 min of walking or aerobic dance reduces blood glucose but does not cause hypoglycemia. Further, the results suggest that 40 min of walking or aerobic dance does not expose the mother to serious metabolic consequences that might adversely affect the fetus.

Physical and psychological decline is common in the post-treatment breast cancer population, yet the efficacy of concurrent interventions to meet both physical- psychosocial needs in this population has not been extensively examined. PURPOSE: This study explores the effects of a combined exercise and psychosocial intervention model on selected physiological-psychological parameters in post-treated breast cancer. METHODS: Forty-one breast cancer survivors were randomly assigned to one of four groups for an 8-week intervention: exercise only [EX, n=13] (aerobic and resistance training), psychosocial therapy only [PS, n=11] (biofeedback), combined EX and PS [EX+PS, n=11], or to control conditions [CO, n=6]. Mean delta score (post-intervention - baseline) were calculated for each of the following: body weight, % body fat (skin folds), predicted VO2max (Modified Bruce Protocol), overall dynamic muscular endurance [OME] (RMCRI protocol), static balance (Single leg stance test), dynamic balance (360° turn and 4-square step test), fatigue (Revised Piper Scale), and quality of life (FACT-B). A one-way ANOVA was used to analyze the preliminary results of this on-going randomized trial. RESULTS: Overall, there were significant differences in the delta scores for predicted VO2max, OME, and dynamic balance among the 4 groups (p

This study compares the resting reproductive hormonal profiles of untrained (N = 11) and endurance-trained (N = 11) males. Testosterone, free testosterone, estradiol, luteinizing hormone (LH), prolactin, and cortisol were measured by radioimmunoassay in resting blood samples (8 h fast) collected every 60 min for 4 h. The endurance-trained group had been active for (mean +/- SE) 12.4 +/- 6.7 yr, 6.6 +/- 0.2 d.wk-1, 68.5 +/- 4.4 min.d-1, while the untrained group was sedentary. Neither group had histories of hypothalamic-pituitary-testicular disorders. The overall 4 h mean testosterone and free testosterone levels were significantly (P less than 0.05) lower in the trained group (4.99 +/- 0.46 vs 7.25 +/- 0.67 ng.ml-1, and 17.2 +/- 1.4 vs 23.6 +/- 0.6 pg.ml-1, for the trained and untrained groups, respectively). The LH of the endurance-trained group was higher (15.3 +/- 1.9 vs 11.7 +/- 1.2 mIU.ml-1, P = 0.06); however, LH pulse frequency and amplitude did not differ between groups. An enhanced estradiol feedback to the hypothalamus-pituitary could not account for the elevated LH, as estradiol levels were similar in the groups. Prolactin and cortisol levels were normal and did not differ between groups. The results suggested normal hypothalamic-pituitary function existed in the trained subjects, and prolactin and cortisol were not causative factors in the lowered resting testosterone and free testosterone levels. The findings indicate that chronic endurance training lowers testosterone and free testosterone in males possibly by impairing testicular function.