PMID 31336654

Research
All papers

Initial Dietary Protein Intake Influence Muscle Function Adaptations in Older Men and Women Following High-Intensity Interval Training Combined with Citrulline

Buckinx F, Marcangeli V, Pinheiro Carvalho L, Dulac M, Hajj Boutros G, Gouspillou G, Gaudreau P, Morais J, Noirez P, Aubertin-Leheudre M

Question

Does baseline dietary protein intake modify the effects of citrulline plus HIIT or placebo plus HIIT on body composition, muscle strength, power, and functional capacity in obese older adults?

Summary

This a posteriori analysis used completers from a 12-week supervised elliptical HIIT trial in obese older adults who also received blinded citrulline or placebo. All groups improved body composition, strength, power, and functional outcomes, and citrulline appeared most helpful among participants with lower baseline protein intake, but the analysis cannot isolate HIIT alone because everyone trained.

Methodology

  • Sedentary obese older men and women who completed the HIIT plus citrulline/placebo trial.
  • 73 participants.
  • Elliptical trainer.
  • Work intervals: 30 seconds.
  • Recovery: 90 seconds moderate intensity.
  • Intensity: 80-85% MHR or Borg >17 during high intervals.
  • 30 minutes.
  • 3 sessions/week.
  • 12 weeks.
  • A posteriori subgroup analysis of a double-blind randomized controlled supplementation trial where all groups completed HIIT
  • Body composition, Handgrip strength, Knee extensor strength, and Functional capacity were tracked.

Outcomes

Overall parameters

All four HIIT plus supplement/placebo/protein-intake groups improved the measured parameters.

Article reports four groups improved significantly regarding all measured parameters.

Improved

Gynoid fat

CIT-PROT- decreased gynoid fat more than PLA-PROT- and CIT-PROT+.

p=0.04 versus PLA-PROT-; p=0.02 versus CIT-PROT+.

Improved

Strength

CIT-PROT+ improved knee extensor strength more than PLA-PROT+, while CIT-PROT- improved relative handgrip more than CIT-PROT+.

KESr p=0.04; HSr p=0.02.

Mixed

Protein intake

Baseline protein intake appeared relevant in citrulline groups but not placebo groups.

No significant placebo-group differences by protein intake.

Mixed

Insights

  • Low-impact elliptical HIIT may be a useful format for obese older adults.
  • Protein intake can be a relevant context variable when evaluating supplement plus exercise outcomes.
  • Do not use this analysis to claim HIIT alone caused the between-group differences.

Limitations

  • A posteriori subgroup analysis
  • Small subgroups
  • No no-exercise or citrulline-only control
  • Protein intake not randomized or controlled
  • Actual attendance/adherence rate not fully reported beyond >=80% inclusion threshold and exclusions

Safety

  • Article did not report adverse events or injuries.
  • Safety context included PAR-Q/no contraindication screening, no orthopedic limitations, major neurological/cardiovascular/lung/cognitive disease exclusions, low-impact elliptical HIIT, and kinesiologist-supervised HR/RPE monitoring.
  • Out of 107 eligible parent-trial participants, 83 completed the 12-week HIIT intervention; 9 refused, 15 were excluded for adherence <80%, and 10 completers were later excluded from this analysis for incomplete food data.