Intensified training in adolescent female athletes: a crossover study of Greek yogurt effects on indices of recovery

ABSTRACT

Background

During a period of intensified exercise (e.g. training/identification camps), often undertaken by competitive youth athletes, the maintenance of muscle function and peak performance can become challenging due to an accumulation of fatigue. The provision of post-exercise dairy protein in adults has been previously shown to accelerate recovery; however, its efficacy in youth athletes is currently unknown. Therefore, the purpose of this study was to examine the effects of increased dairy protein consumption with plain Greek yogurt (GY) on performance and recovery indices during an intensified soccer training camp in adolescent female soccer players.

Methods

Thirteen players (14.3 ± 1.3 years) participated in a randomized, double blinded, crossover design study where they received 3 servings/day of either GY (~115 kcal, 17 g protein, ~11.5 g carbohydrates) or an isoenergetic carbohydrate control (CHO, ~115 kcal, 0.04 g protein, ~28.6 g carbohydrates) during two 5-day soccer-specific training camps. Performance was assessed before and after each training camp. Fasted, morning, creatine kinase (CK), insulin-like growth factor-1 (IGF-1), C-reactive protein (CRP), interleukin 6 (IL6), interleukin 10 (IL10) and tumor necrosis factor-α (TNFα) were measured in plasma pre- and post-training.

Results

Training led to decrements in counter-movement jump (p = 0.01), broad jump (p = 0.04) and aerobic capacity (p = 0.006), with no effect of GY. A significant increase in anti-inflammatory cytokine IL10 was observed from pre- to post-training in GY (+26% [p = 0.008]) but not in CHO (p = 0.89). CRP and CK increased (+65% [p = 0.005] and +119% [p ≤ 0.001], respectively), while IGF-1 decreased (−34% [p ≤ 0.001]) from pre- to post-training with no difference between conditions.

Conclusions

These results demonstrate that consumption of GY did not offer any added recovery benefit with respect to measures of performance and in the attenuation of exercise-induced muscle damage above that achieved with energy-matched carbohydrate in this group of young female soccer players. However, regular consumption of GY may assist with the acute anti-inflammatory response during periods of intensified training in adolescent athletes.

KEYWORDS:

• Protein
• carbohydrates
• cytokines
• creatine kinase
• C-reactive protein

Acknowledgments

We would like to thank all our participants, their parents, and coaches for participating in our study, students who helped with data collection (Beigpoor A., McKee K., Nasato M., Harten D. and Stoikos J.), as well as the phlebotomists for their assistance. We would also like to thank Sheridan College Institute of Technology and Advanced Learning (Ontario, Canada) and the Brock Sports Performance Centre who provided in-kind contribution by donating equipment and staff for the performance assessment.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. The data are not publicly available due to REB restrictions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

BJM, PK, BF: conceptualization of study design and project administration. BJM, PK, BF, ARJ, BDR: methodology. BJM, PW, PK, BF: data analysis and interpretation. BJM, PW, SO, SW, NK, BF, PK: data collection. BJM: writing of original draft. PK, BF, ARJ, BDR, PW, NK: review and editing. All authors have read and agreed to the published version of the manuscript.

Additional information

Funding

This study was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC grant to P. Klentrou # 2015-04424). B.J. McKinlay held an Own the Podium - Mitacs IT08117 Doctoral Scholarship and currently holds an Ontario Graduate Scholarship. P.J. Wallace and N. Kurgan hold an NSERC doctoral scholarship, and S. Woods holds an Ontario Graduate Scholarship.