The impact of feedback on dietary intake and body composition of collegiate women volleyball players over a competitive season.


Journal(Medline/Pubmed accepted abbreviation): J Strength Cond Res
Year:2010
Volume:24
Number:8
Page numbers:2220-2226

Summary of Background and Research Design


Hypothesis: To assess whether feedback to volleyball players on their dietary intake would increase nutrient intakes or improve body composition.

Subjects:In a 2-year study, 15 female collegiate volleyball players participated in the first year and 15 completed in the second year. A total of 8 of these players completed both years of the study and these data were presented.

Experimental design:Longitudinal study with feedback or no feedback on dietary analysis as the intervention.

Treatments and protocol:In the first year of the study (baseline), dietary intake (3-day food records) and body composition data were collected at the beginning, peak, and end of the season. Computerized nutrient analysis was done on the food record data, but no feedback on the results of the analysis was given to the participants. The second year of the study was essentially a repeat of the first year except that this time feedback was given to the participants regarding their individual nutrient intakes and those of the team as a whole.

Summary of Research Findings
  • When measured at the beginning of the season, feedback increased the intake of protein (1.5 g/kg body weight/day) versus baseline (1.1 g/kg body weight/day). Also at the beginning of the season, feedback increased the intake of vitamin C (314% DRI versus 96% DRI) and calcium (152% DRI versus 102% DRI).
  • The differences in protein, iron, and calcium caused by feedback at the beginning of the season did not persist into the peak or after season measurements.
  • Feedback did not influence the intake of energy or the body composition of the subjects. It also did not influence the intakes of other vitamins and minerals.
  • For several nutrients, over half of the volleyball players had nutrient intakes below 90% of the DRI at different points in the season

Interpretation of findings/Key practice applications:

This study indicates that feedback on nutrient analysis results was able to increase the intakes of protein, vitamin C, and calcium versus no feedback. However, the increase was not consistent at all points during the season and the intakes of several other nutrients were not altered by feedback. There were a couple of key limitations to this study. First, there were data from only 8 players for both year 1 and year 2. Due to the small sample size, there were large standard errors associated with several of the means presented, which may have precluded the detection of differences that might have been statistically significant in a study with larger sample size. Second, this issue of dietary supplements for these nutrients was not specifically addressed in this paper and it is not clear how the author dealt with this issue.
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