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  • Author: Vicki J. Harber x
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Karen J. Reading, Linda J. McCargar and Vicki J. Harber

Menstrual abnormalities are associated with negative energy balance and reduced energy expenditure (REE). To examine this relationship in elite adolescent aesthetic athletes, 3 groups of females (aged 15-18 years) were studied: 10 oligo/amenorrheic athletes (OA), 11 eumenorrheic athletes (EA), and 8 non-athlete controls (C). Components of energy balance, body composition, dietary restraint, pubertal maturation, and luteal phase salivary progesterone were assessed in all groups. Both groups of athletes had a later age of menarche and lowerpubertal development score compared to the non-athletes (p < .05). With the exception of salivary progesterone (ng/ml; OA = 0.15±0.01 <EA = 0.29± 0.1 and C = 0.30 ± 0.13, /p = .007), there were no differences between the athlete groups. Energy balance (kcal/d) in the OA group was lower (−290 ± 677) compared to either EA (−5±461) or C (179 ± 592) but did not reach significance (p = .24). Dietary energy intake and absolute REE (kcal/d) were not different among groups, despite detectable differences in reproductive status, and thus could not be attributed to differences in energy balance or REE.

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Scott C. Forbes, Vicki Harber and Gordon J. Bell

Acute resistance exercise and L-arginine have both been shown to independently elevate plasma growth hormone (GH) concentrations; however, their combined effect is controversial. The purpose was to investigate the combined effects of resistance exercise and L-arginine supplementation on plasma L-arginine, GH, GH secretagogues, and IGF-1 in strength trained participants. Fourteen strength trained males (age: 25 ± 4 y; body mass: 81.4 ± 9.0 kg; height: 179.4 ± 6.9 cm; and training experience: 6.3 ± 3.4 y) participated in a randomized double-blind crossover design (separated by ~7 days). Subjects reported to the laboratory at 08:00 in a fasted state, consumed L-arginine (ARG; 0.075 g·kg−1 body mass) or a placebo (PLA) before performing an acute bout of resistance exercise (3 sets of 8 exercises, 10 repetitions at ~75% 1RM). Blood samples were collected at rest, before exercise, and at 0, 15, 30, and 60 min of rest-recovery. The ARG condition significantly increased plasma L-arginine concentrations (~120%) while no change was detected in the PLA condition. There were no differences between conditions for GH, GH-releasing hormone, ghrelin, or IGF-1 at any time point. GH-inhibiting hormone was significantly lower in the ARG condition. However, integrated area under the curve for GH was blunted in the ARG condition (L-arginine = 288.4 ± 368.7 vs. placebo = 487.9 ± 482.0 min·ng·mL−1, p < .05). L-arginine ingested before resistance exercise significantly elevated plasma L-arginine concentration but attenuated plasma GH in strength trained individuals despite a lower GHIH. Furthermore our data shows that the GH suppression was not due to a GH or IGF-1 induced autonegative feedback loop.

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Scott C. Forbes, Vicki Harber and Gordon J. Bell

L-arginine may enhance endurance performance mediated by two primary mechanisms including enhanced secretion of endogenous growth hormone (GH) and as a precursor of nitric oxide (NO); however, research in trained participants has been equivocal. The purpose was to investigate the effect of acute L-arginine ingestion on the hormonal and metabolic response during submaximal exercise in trained cyclists. Fifteen aerobically trained men (age: 28 ± 5 y; body mass: 77.4 ± 9.5 kg; height: 180.9 ± 7.9 cm; VO2max: 59.6 ± 5.9 ml·kg-1·min−1) participated in a randomized, double-blind, crossover study. Subjects consumed L-arginine (ARG; 0.075 g·kg-1 body mass) or a placebo (PLA) before performing an acute bout of submaximal exercise (60 min at 80% of power output achieved at ventilatory threshold). The ARG condition significantly increased plasma L-arginine concentrations (~146%), while no change was detected in the PLA condition. There were no differences between conditions for GH, nonesterified fatty acids (NEFA), lactate, glucose, VO2, VCO2, RER, CHO oxidation, and NOx. There was reduced fat oxidation at the start of exercise (ARG: 0.36 ± 0.25 vs. PLA: 0.42 ± 0.23 g·min−1, p < .05) and an elevated plasma glycerol concentrations at the 45-min time point (ARG: 340.3 vs. PLA: 288.5 μmol·L-1, p < .05) after L-arginine consumption. In conclusion, the acute ingestion of L-arginine did not alter any hormonal, metabolic, or cardio-respiratory responses during submaximal exercise except for a small but significant increase in glycerol at the 45-min time point and a reduction in fat oxidation at the start of exercise.

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Michael A. Penkman, Catherine J. Field, Christopher M. Sellar, Vicki J. Harber and Gordon J. Bell

Purpose:

This study determined the effect of dehydration and rehydration (DR) on performance, immune cell response, and tympanic temperature after high-intensity rowing exercis.

Methods:

Seven oarswomen completed two simulated 2000-m rowing race trials separated by 72 h in a random, cross-over design. One trial was completed in a euhydrated (E) condition and the other using a DR protocol.

Results:

The DR condition resulted in a 3.33 ± 0.14% reduction in body mass (P < .05) over a 24-h period followed by a 2-h rehydration period immediately before the simulated rowing race. There was a greater change in tympanic temperature observed in the DR trial (P < .05). There were increases in the blood concentration of leukocytes, lymphocytes, lymphocyte subsets (CD3+, CD3+/4+, CD3+/8+, CD3/16+, CD4+/25+; P < .05) and decreases in lymphocyte proliferation and neutrophil oxidative burst activity immediately following the simulated race (P < .05) in both trials. Blood leukocyte and neutrophil concentrations were greater after exercise in the DR trial (P < .05). Whereas most immune measures returned to resting values after 60 min of recovery in both trials, lymphocyte proliferation and the concentrations of CD3+/4+ and CD4+/25+ cells were significantly lower than before exercise. Blood leukocyte and neutrophil concentrations were significantly higher before and after exercise in the E trial.

Conclusion:

The effects of dehydration/rehydration did not negatively influence simulated 2000-m rowing race performance in lightweight oarswomen but did produce a higher tympanic temperature and had a differential effect on blood leukocyte, neutrophil, and natural killer (CD3/16+) cell concentrations after exercise compared with the euhydrated state.

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Daniel G. Syrotuik, Kirsten L. MacFadyen, Vicki J. Harber and Gordon J. Bell

To examine the effects of elk velvet antler supplementation (EVA) combined with training on resting and exercise-stimulated hormonal response, male (n = 25) and female (n = 21) rowers ingested either E VA (560 mg/d) or placebo (PL) during 10 wk of training. VO2max, 2000 m rowing time, leg and bench press strength were determined before and after 5 and 10 wk of training. Serum hormone levels were measured prior to and 5 and 60 min after a simulated 2000 m rowing race. VO2max and strength increased and 2000 m times decreased similarly (P < 0.05) with training. There was no significant difference between the EVA and PL group for any hormonal response. Testosterone (males only) and growth hormone (both genders) were higher 5 min after the simulated race (P < 0.05) but returned to baseline at 60 min. Cortisol was higher 5 and 60 min compared to rest (both genders) (P < 0.05) and was higher 60 min post-exercise following 5 and 10 wk of training. It appears that 10 wk of EVA supplementation does not significantly improve rowing performance nor alter hormonal responses at rest or after acute exercise than training alone.

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Gordon J. Bell, Vicki Harber, Terra Murray, Kerry S. Courneya and Wendy Rodgers

Background:

Fitness and health variables were measured in 128 sedentary men and women randomly assigned to 6 months of fitness training (F), a walking program (W), or a control (C) group.

Methods:

The F program gradually increased volume and intensity until 4 d/wk of training, at 70% of peak VO2 for 43 min/session was prescribed while the W group performed daily walking monitored with pedometers and increased until 10,000 steps×d−1 were prescribed. Total weekly energy expenditure was matched between the activity groups. The control group was asked to maintain their usual activity.

Results:

Body mass, waist circumference, waist/hip ratio, resting HR were reduced in all groups after 6 months (P < .05). Fasting glucose, glucose tolerance, and total cholesterol were similarly improved in all groups (P < .05). Blood pressure and HR decreased during submaximal exercise in all groups (P < .05) but rating of perceived exertion (RPE) was decreased only in the F group (P < .05). Only the F participants showed a significant increase in ventilatory threshold (VT; ~15%) and peak VO2 (~9%) after 6 months.

Conclusions:

Supervised fitness training in previously sedentary adults produced greater improvements in submaximal RPE, BPsys, VT, and peak VO2 but not other fitness and health-related variables compared with a pedometer-based walking program matched for total energy cost.