Predisposing Risk Factors for Stress Fractures in Collegiate Cross-Country Runners.

ABSTRACT: Giffin, KL, Knight, KB, Bass, MA, and Valliant, MW. Predisposing risk factors and stress fractures in collegiate cross-country runners. J Strength Cond Res 35(1): 227-232, 2021-The purpose of this study was to explore factors associated with increased stress fractures in collegiate cross-country runners. Subjects in this study were 42 male and female cross-country runners at a Division I university. Each athlete completed a questionnaire regarding smoking status, vitamin/mineral intake, previous stress fracture history, birth control usage, menstrual status, and demographic information. Nutritional assessment using a 3-day food record and measurements of whole body, lumbar spine, and hip bone mineral densities (BMDs) were also conducted on each athlete. Results indicated that 40% of the female and 35% of the male runners reported a history of stress fracture, and that all of them did not meet the recommended daily energy intake or adequate intakes for calcium or vitamin D required for their amount of training. Two-tailed t-test found statistically higher incidences of lumbar spine BMD in male and female runners whose daily calcium and vitamin D intakes were below minimum requirements as well as for women whose caloric intake was below the required level. When data on the lumbar spine was evaluated, 31% of subjects (31.8% of the male and 30% of the female runners) were identified as having osteopenia and 4.8% with osteoporosis. Results warrant a need for future longitudinal studies.

Effects of Jaw Clenching and Jaw Alignment Mouthpiece Use on Force Production During Vertical Jump and Isometric Clean Pull.

Allen, CR, Fu, Y-C, Cazas-Moreno, V, Valliant, MW, Gdovin, JR, Williams, CC, and Garner, JC. Effects of jaw clenching and jaw alignment mouthpiece use on force production during vertical jump and isometric clean pull. J Strength Cond Res 32(1): 237-243, 2018-This study examined the effects of jaw clenching, a self-adapted, jaw-repositioning mouthpiece on force production during maximum countermovement vertical jump and maximum isometric midthigh clean pull assessments in an attempt to determine any ergogenic effect attributable to clenching, jaw-repositioning mouthpiece use, or the combination of both. Thirty-six male subjects performed vertical jump and isometric clean pull assessments from a force platform under various mouthpiece and clench conditions. A 3 × 2 (mouthpiece × clench) repeated-measures analysis of variance was conducted to analyze each of the following force production variables for both assessments: peak force, normalized peak force, and rate of force development. In addition, jump height was analyzed for the vertical jump. Results revealed improvements in peak force (F1,35 = 15.84, p ≤ 0.001, (Equation is included in full-text article.)= 0.31), normalized peak force (F1,35 = 16.28, p ≤ 0.001, (Equation is included in full-text article.)= 0.32), and rate of force development (F1,35 = 12.89, p = 0.001, (Equation is included in full-text article.)= 0.27) during the isometric clean pull assessment when participants maximally clenched their jaw, regardless of mouthpiece condition. There were no statistically significant differences in jump height, peak force, normalized peak force, or rate of force development during the vertical jump for any treatment condition. This study supports previous research demonstrating that the implementation of remote voluntary contractions such as jaw clenching can lead to concurrent activation potentiation and a resulting ergogenic effect during activities involving and requiring high-force production.

Association between athletic participation and the risk of eating disorder and body dissatisfaction in college students.

OBJECTIVE: Given that females exhibit a greater prevalence of eating disorders, there is of yet no conclusive evidence whether participation in college athletics exacerbates eating disorders or body shape dissatisfaction. This study assessed how gender and participation in collegiate athletics are associated with increased risk for disordered eating attitudes and body shape concerns in college students. METHODS: This study used a cross-sectional research design. A total of 302 students at a Southern US university fully completed the eating attitudes test and the body shape questionnaire during class time or team meetings. Logistic regression was conducted to determine risk differentials for each group. RESULTS: Of 302 students, 65.6% were females and 63.2% were non-athletes. Athletic status was significant as well but became slightly less so with adjustment (unadjusted at OR = 3.14, P < 0.001 vs. adjusted OR = 3.22, P < 0.001). Moreover, it was found that that non-athletic female students are slightly more at risk for disordered eating and significantly more dissatisfied with their body shape (OR = 5.95, P < 0.001). CONCLUSIONS: Although there seems to still be many unresolved issues regarding eating disorders, one thing is clear females are at higher risk, and it remains a significant challenge to college health services. College health practitioners should be made aware of the significant effect stress has on freshman in particular.

A Prospective Study Comparing Distance-based vs. Time-based Exercise Prescriptions of Walking and Running in Previously Sedentary Overweight Adults.

Prior work has reported that the declines observed in body mass index (BMI) and circumference measurements in their cross-sectional data were twice as large when calculated from distance energy expenditure estimations compared to energy expenditure estimations based on time and intensity. The primary purpose of this study was to compare walking/running for distance to walking/running for time as part of an exercise intervention. This study followed a between-subjects, repeated measures design. Fifteen overweight, but otherwise healthy participants completed the study. The time-based group walked/ran for self-reported time while the distance-based group walked/ran for self-reported distance. A mixed-factor repeated-measures ANOVA was used to compare all dependent variables both within-subjects and between-subjects. Weekly adherence rates to the exercise program did not exhibit a significant difference (p > 0.05). Significant interactions were shown for mean body mass loss between groups as well as mean blood glucose level (p < 0.05). Distance-based group exhibited a decline in body mass and blood glucose while the time-based group exhibited an increase in both variables. To the best of the authors' knowledge, the present study is the first to directly compare a distance-based vs. a time-based exercise program for walking and running for improvement of risk factors of cardiovascular disease. The results of this study would suggest that a distance-based exercise prescription of walking or running should provide a clinician or researcher with a closer estimation of overall accumulated exercise and resultant weight loss.

Nutrition education by a registered dietitian improves dietary intake and nutrition knowledge of a NCAA female volleyball team.

Eleven female participants from a NCAA Division I volleyball team were evaluated for adequate energy and macronutrient intake during two off-seasons. Total energy and macronutrient intake were assessed by food records and results were compared against estimated needs using the Nelson equation. Dietary intervention was employed regarding the individual dietary needs of each athlete as well as a pre- and post-sports nutrition knowledge survey. Post dietary intervention, total energy, and macronutrient intake improved, as well as a significant improvement in sports nutrition knowledge (p < 0.001). Nutrition education is useful in improving dietary intake and nutrition knowledge of female athletes.

Higher amounts of body fat are associated with inadequate intakes of calcium and vitamin D in African American women.

Calcium and vitamin D are associated with obesity. We hypothesized that African American women with higher calcium and vitamin D intakes would have lower body fat compared with women with lower calcium and vitamin D intakes. This cross-sectional study included 100 premenopausal African American women aged 18 to 40 years with a spectrum of body mass indices (17.3-46.7 kg/m(2)). Dietary information was obtained using 24-h recalls. Total body fat was determined by dual-energy x-ray absorptiometry and reported as percentage body fat (%BF). Subjects' data were divided into 2 groups (n = 50 per group) based on the median quartile of %BF, and differences were determined using independent t tests. Women with at least 37.9%BF had mean calcium (mg per day ± SD) and vitamin D intakes (µg per day ± SD) of 528.6 ± 146.0 and 3.8 ± .9, respectively. In comparison, women with lower %BF (<37.9%) had higher (P < .001) calcium and vitamin D intakes of 911.5 ± 208.3 and 5.0 ± 0.8, respectively. Partial correlation coefficients (controlling for the confounding variables of fat, carbohydrate, and protein intakes) indicated significant (P < 0.001) inverse associations between calcium intake and %BF (r = -.666), and vitamin D and %BF (r = -.460) in the 100 women. In conclusion, women with lower intakes of calcium and vitamin D were more likely to exhibit excessive adiposity compared with women with higher intakes.