title: Three Days of Intermittent Fasting: Repeated-Sprint Performance Decreased by Vertical-Stiffness Impairment.
abstract: OBJECTIVE
  To examine the effects of 3 d of intermittent fasting (3d-IF: abstaining from eating/drinking from dawn to sunset) on physical performance and metabolic responses to repeated sprints (RSs).
  
  
  METHODS
  Twenty-one active males performed an RS test (2 sets: 5 × 5-s maximal sprints with 25 s of recovery between and 3 min of recovery between sets on an instrumented treadmill) in 2 conditions: counterbalanced fed/control session (CS) and fasting session (FS). Biomechanical and biochemical markers were assessed preexercise and postexercise.
  
  
  RESULTS
  Significant main effects of IF were observed for sprints: maximal speed (P = .016), mean speed (P = .015), maximal power (P = .035), mean power (P = .049), vertical stiffness (P = .032), and vertical center-of-mass displacement (P = .047). Sprint speed and vertical stiffness decreased during the 1st (P = .003 and P = .005) and 2nd sprints (P = .046 and P = .048) of set 2, respectively. Postexercise insulin decreased in CS (P = .023) but not in FS (P = .230). Free-fatty-acid levels were higher in FS than in CS at preexercise (P < .001) and at postexercise (P = .009). High-density lipoprotein cholesterol (HDL-C) was higher at postexercise in FS (1.32 ± 0.22 mmol/L) than in CS (1.26 ± 0.21 mmol/L, P = .039). The triglyceride (TG) concentration was decreased in FS (P < .05) compared with CS.
  
  
  CONCLUSIONS
  3d-IF impaired speed and power through a decrease in vertical stiffness during the initial runs of the 2nd set of RS. The findings of the current study confirmed the benefits of 3d-IF: improved HDL-C and TG profiles while maintaining total cholesterol and low-density lipoprotein cholesterol levels. Moreover, improving muscle power might be a key factor to retain a higher vertical stiffness and to partly counteract the negative effects of intermittent fasting.
authors.forename: Anissa
authors.initials: A
authors.lastname: Cherif
authors.forename: Romain
authors.initials: R
authors.lastname: Meeusen
authors.forename: Abdulaziz
authors.initials: A
authors.lastname: Farooq
authors.forename: Joong
authors.initials: J
authors.lastname: Ryu
authors.forename: Mohamed Amine
authors.initials: MA
authors.lastname: Fenneni
authors.forename: Zoran
authors.initials: Z
authors.lastname: Nikolovski
authors.forename: Sittana
authors.initials: S
authors.lastname: Elshafie
authors.forename: Karim
authors.initials: K
authors.lastname: Chamari
authors.forename: Bart
authors.initials: B
authors.lastname: Roelands
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001696:Biomechanical Phenomena; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D005215:Fasting / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006728:Hormones / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007514:Islam; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D012420:Running / Q000502:physiology*; D013997:Time Factors; D014280:Triglycerides / Q000097:blood
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D005230:Fatty Acids, Nonesterified; D006728:Hormones; D007328:Insulin; D014280:Triglycerides
keywords: RSA; anaerobic exercise; biochemical parameters; glyconeogenesis; mechanical-output variables; repeated-sprint ability