Effect of Protein Quality During Overreaching in Trained Cyclists

Monitoring Exercise Performance and Mitigating Training Stress in Endurance-trained Cyclists

Athletes frequently undertake periods of intensified training commonly referred to as "overreaching." These training periods acutely decrease performance, with the expectation that performance will rebound and improve after a short recovery. Yet, overreaching does not always improve performance and may be a precursor to overtraining syndrome, a long-term decrement in performance. A nutritional intervention focused on the adoption of 'best practices' for protein feeding (optimal timing, dose, and quality) could help reduce the stress of overreaching, reduce the likelihood of developing overtraining syndrome, and augment adaptations to intensified exercise. While the nutrition study is our main interest, the investigators first want to validate the measurement of exercise performance. Accordingly, this project consists of two related studies: (1) the assessment of short time trials for reliability and validity; and (2) the assessment of optimal protein feeding to decrease the stress of overreaching and improve outcomes following training.

Endurance-trained athletes frequently undergo periods of overreaching (increased training loads) to improve performance. In study 1, the investigators will determine whether 4-min and 20-min time trials are repeatable and whether they (individually or collectively) relate to 1-hour time trial performance. For Study 2, the investigators propose that proper nutrition (with a focus on the dose, timing, and quality of protein) can help mitigate the stress of overreaching, which will improve performance. Thus, the investigators will compare the effects of two diets that differ in terms of protein servings (dose, timing, quality). In Study 2, skeletal muscle biopsies will be collected to determine how dietary protein intervention impacts the quality and quantity of skeletal muscle mitochondria in response to intense training.

For study 1, the objective is to determine the reliability and validity of 4-min and 20-min time trial performance (mean power output).

For study 2, the objective is to (1) determine whether following an optimal protein diet during a period of intense training will, relative to a typical diet: (1) improve measures of exercise performance, (2) improve sleep quality, psychological wellbeing, and immune function, (3) improve the quality and quantity of skeletal muscle mitochondria.

Study 1 is a reliability and validity experiment designed to assess the key outcome measure in study 2.

Study 2 is a randomized, crossover study. Participants will, in a randomized order, complete both conditions, separated by a 4-day washout period.

Inclusion Criteria:

• non-smokers
• non-diabetic
• Participants had to be training regularly (performing aerobic exercise at least 4 times per week, including regular cycling exercise)
• Generally healthy

Exclusion Criteria:

• consuming excessive alcohol (>21 units per week)
• use of an investigational drug or nutraceutical in the previous 30 days
• dairy allergy
• history of significant loss or gain of body mass in the past 6 months (>2kg)
• regular use of non-steroidal anti-inflammatory drugs
• infectious disease, and/or the presence of any relevant disease (e.g., gastrointestinal, cardiovascular, neuromuscular, etc.).