Calcium intake and its association with dieting behavior were assessed in female adolescents competing in an aesthetic and a nonaesthetic sport (gymnastics and speed skating). Athletes were 25 skaters and 32 gymnasts competing at a provincial level or higher. Calcium intake was assessed by food frequency questionnaire; dieting behavior by the Eating Attitudes Test Dieting subscale; and body composition by skinfolds, height, and weight. Mean calcium intakes of both groups of athletes exceeded Canadian recommendations, and skaters' mean intakes exceeded U.S. recommendations; however, many individuals had low intakes. Gymnasts were leaner than skaters and had lower calcium intakes, but this difference was not associated with Dieting subscale scores, which were similar between sports and were not correlated with calcium intake. Athletes had higher mean calcium intakes than normally active adolescents studied (measured with a similar protocol) and had lower Dieting subscale scores. Thus, although calcium intakes of some athletes require attention, sport participation was associated with increased intakes. Also, for these athletes, dieting behavior did not directly interfere with calcium intake.
Brenda L. Webster and Susan I. Barr
Jennifer L. Krempien and Susan I. Barr
Energy intakes of adults with spinal cord injury (SCI) have been reported to be relatively low, with many micronutrients below recommended amounts, but little is known about the diets of athletes with SCI. The purpose of this cross-sectional, observational study was to assess energy intakes and estimate the prevalence of dietary inadequacy in a sample of elite Canadian athletes with SCI (n = 32). Three-day self-reported food diaries completed at home and training camp were analyzed for energy (kcal), macronutrients, vitamins, and minerals and compared with the dietary reference intakes (DRIs). The prevalence of nutrient inadequacy was estimated by the proportion of athletes with mean intakes below the estimated average requirement (EAR). Energy intakes were 2,156 ± 431 kcal for men and 1,991 ± 510 kcal for women. Macronutrient intakes were within the acceptable macronutrient distribution ranges. While at training camp, >25% of men had intakes below the EAR for calcium, magnesium, zinc, riboflavin, folate, vitamin B12, and vitamin D. Thiamin, riboflavin, calcium, and vitamin D intakes were higher at home than training camp. Over 25% of women had intakes below the EAR for calcium, magnesium, folate, and vitamin D, with no significant differences in mean intakes between home and training camp. Vitamin/mineral supplement use significantly increased men’s intakes of most nutrients but did not affect prevalence of inadequacy. Women’s intakes did not change significantly with vitamin/mineral supplementation. These results demonstrate that athletes with SCI are at risk for several nutrient inadequacies relative to the DRIs.
Susan I. Barr and Heather A. McKay
The maximal amount of bone mass gained during growth (peak bone mass) is an important determinant of bone mass in later life and thereby an important determinant of fraeiure risk. Although genetic factors appear lo be primary determinants of peak bone mass, environmental factors such as physical activity and nutrition also contribute. In this article, bone growth and maintenance are reviewed, and mechanisms are described whereby physical activity can affect bone mass. Studies addressing the effects of physical activity on bone status in youth are reviewed: Although conclusive data are not yet available, considerable evidence supports the importance of activity, especially activity initiated before puberty. The critical role of energy in bone growth is outlined, and studies assessing the impact of calcium intake during childhood and adolescence are reviewed. Although results of intervention trials are equivocal, other evidence supports a role for calcium intake during growth. Recommendations for physical activity and nutrition, directed lochildren and adolescents, are presented.
Nanci S. Guest and Susan I. Barr
High levels of cognitive dietary restraint (CDR) have been associated with subclinical menstrual cycle irregularities and increased cortisol levels, both of which can affect bone mineral density (BMD). Low BMD has been implicated in stress fracture risk. We assessed CDR in female runners (≥ 20 km/wk) with a recent stress fracture (SF) and with no stress fracture history (NSF). A sample of 79 runners (n = 38 SF, 29 ± 5 y; n = 41 NSF, 29 ± 6 y) completed a 3-d food record and questionnaire assessing physical activity, menstrual cycle history, and perceived stress. SF and NSF runners had similar body mass index (21.2 ± 1.8 vs. 22.0 ± 2.5 kg/m2), physical activity (35.7 ± 13.5 vs. 33.4 ± 1.34 km/wk), perceived stress, and dietary intakes. CDR, however, was higher in SF runners (11.0 ± 5.4 vs. 8.4 ± 4.3, P < 0.05). Subclinical menstrual cycle disturbances and increased cortisol levels that are associated with high CDR, might in turn contribute to lowered BMD and increased stress fracture risk.
Kristin E. MacLeod, Sean F. Nugent, Susan I. Barr, Michael S. Koehle, Benjamin C. Sporer, and Martin J. MacInnis
Beetroot juice (BR) has been shown to lower the oxygen cost of exercise in normoxia and may have similar effects in hypoxia. We investigated the effect of BR on steady-state exercise economy and 10-km time trial (TT) performance in normoxia and moderate hypoxia (simulated altitude: ~2500 m). Eleven trained male cyclists (VO2peak ≥ 60 ml·kg-1·min-1) completed four exercise trials. Two hours before exercise, subjects consumed 70 mL BR (~6 mmol nitrate) or placebo (nitrate-depleted BR) in a randomized, double-blind manner. Subjects then completed a 15-min self-selected cycling warm-up, a 15-min steady-state exercise bout at 50% maximum power output, and a 10-km time trial (TT) in either normoxia or hypoxia. Environmental conditions were randomized and single-blind. BR supplementation increased plasma nitrate concentration and fraction of exhaled nitric oxide relative to PL (p < .05 for both comparisons). Economy at 50% power output was similar in hypoxic and normoxic conditions (p > .05), but mean power output was greater in the normoxic TT relative to the hypoxic TT (p < .05). BR did not affect economy, steady-state SpO2, mean power output, or 10-km TT completion time relative to placebo in either normoxia or hypoxia (p > .05 in all comparisons). In conclusion, BR did not lower the oxygen cost of steady-state exercise or improve exercise performance in normoxia or hypoxia in a small sample of well-trained male cyclists.