Nighttime Feeding and Morning Endurance Performance

Not Applicable

Completed

Brief Summary: The purpose of this study is to investigate the influence of a nighttime feeding on next morning running performance, hydration status, and exercise metabolism in female endurance athletes. Specifically, the effect of a chocolate milk beverage will be examined versus a non-nutritive, flavor-matched placebo. The investigators hypothesize that the nighttime consumption of chocolate milk, a whole food complex, will result in improved next morning running performance versus placebo. Secondarily, the investigators hypothesize that any potential positive performance outcomes from the chocolate milk treatment may be due to an enhanced pre-exercise hydration status or improved exercise metabolism.

Detailed Description: This study will be interventional in nature and employ a crossover, randomized, double-blinded approach. This study will include a maximal oxygen uptake test and three trials: one familiarization trial, and two experimental trials. The familiarization will serve as a practice test to minimize any training effects between experimental trials. The experimental trials will be completed within a 2-week period determined by the luteal phase of the menstrual cycle (days 15-28 of the menstrual cycle, with day 1 being the first day of menstruation). A minimum of 48-72 hours will be provided between testing days.

Experimental trials will consist of baseline testing (height, weight, urinalysis, resting metabolic rate), followed by a treadmill performance protocol. Participants will complete a 3-stage incremental exercise test (at 55%, 65%, and 75% of maximal oxygen uptake respectively). Metabolic data will be collected during this time. Participants will then complete a 10-kilometer running time trial in which markers of intensity are monitored at various time points (blood glucose, blood lactate, heart rate, rating of perceived exertion). Participants and primary researchers will be blinded to all time and speed data. Distance will be the only known measure of progress. Additional blood, urine, and body weight measures will be taken immediately post exercise.

Recruitment & Eligibility

Inclusion Criteria

Female
Between the ages of 18 and 40 years old
Consistently use oral contraceptives (greater than 2 months) or be considered eumenorrheic without oral contraceptive use
'Moderately trained,' defined as a weekly mileage ≥ 25 miles for at least 6 months, and a VO2max ≥ 45 ml/kg/min

Exclusion Criteria

Lactose intolerant
Smokers
Uncontrolled thyroid conditions
Uses anti-inflammatory drugs or any dietary supplements intended to improve performance
Have musculoskeletal injury that could limit performance

Arm && Interventions

Group	Intervention	Description
chocolate milk	chocolate milk	In this arm, subjects receive chocolate milk
flavor-matched placebo	flavor-matched placebo	In this arm, subjects receive a flavor-matched placebo

Primary Outcome Measures

Name	Time	Method
Running Performance	24 hours	10K time trial on a treadmill

Secondary Outcome Measures

Name	Time	Method
Urine Specific Gravity	24 hours	Changes in urine specific gravity will be measured pre and post a 10K time trial run on a treadmill
Urine Volume	24 hour	Measurement of total urine output.