analysisathletesbasebikebloodcaffeinecorecorneringcyclistsdopeeffectseliteenduranceep36exercisefatfatiguefitfittingftpgettinghumanintrokneelaplearningleglevelmentalmetabolismmobilitynutritionpainpaulperiodizationpolarizedpowerprimept1pt2raceracingrecommendationsselectionserrasinglesportstrengthstretchingstudiesstudysupplementstaketesttrainingusacvo2maxweatherweightworkyoga