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Updated: Jan 21, 2026

A Real-World High-Intensity Interval Training Protocol for Cardiorespiratory Fitness Improvement
Published on: February 22, 2022
Initial Dietary Protein Intake Influence Muscle Function Adaptations in Older Men and Women Following High-Intensity
Fanny Buckinx1,2,3, Vincent Marcangeli1,2, Lívia Pinheiro Carvalho1,2
1Department of Exercise Science, Groupe de Recherche en Activité Physique Adapté (GRAPA), Université du Québec à Montréal, Montréal, QC H2X 1Y4, Canada.
Background:
This study evaluates whether the initial amount of dietary protein intake could influence the combined effect of high-intensity interval training (HIIT) and citrulline (CIT), or HIIT alone, on body composition, muscle strength, and functional capacities in obese older adults.
Methods:
Seventy-three sedentary obese older men and women who completed a 12-week elliptical HIIT program with double-blinded randomized supplementation of CIT or placebo (PLA) were divided into four groups according to their initial protein intake (CIT-PROT+: n = 21; CIT-PROT-: n = 19; PLA-PROT+: n = 19; PLA-PROT-: n = 14). Body composition (fat and fat-free masses), handgrip (HSr) strength, knee extensor (KESr) strength, muscle power, and functional capacities were measured pre-intervention and post-intervention.
Results:
Following the intervention, the four groups improved significantly regarding all the parameters measured. For the same initial amount of protein intake, the CIT-PROT- group decreased more gynoid fat mass (p = 0.04) than the PLA-PROT- group. The CIT-PROT+ group increased more KESr (p = 0.04) than the PLA-PROT+ group. In addition, the CIT-PROT- group decreased more gynoid FM (p = 0.02) and improved more leg FFM (p = 0.02) and HSr (p = 0.02) than the CIT-PROT+ group.
Conclusion:
HIIT combined with CIT induced greater positive changes than in the PLA groups. The combination seems more beneficial in participants consuming less than 1 g/kg/d of protein, since greater improvements on body composition and muscle strength were observed.
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