Effects of High-Intensity Interval Training and Isoinertial Training on Leg Extensors Muscle Function, Structure, and Intermuscular Adipose Tissue in Older Adults.
Level 3 - non-randomized controlled study
Non-randomized within-subject sequential crossover intervention study.
PubMed 31649552 · doi:10.3389/fphys.2019.01260
What was done
Twelve healthy older men (mean age 69.3 ± 4.2 years) completed 8 weeks of aerobic high-intensity interval training (HIT; 7 × 2-min cycling at 90% peak VO2, 3 times/week) followed by a 4-month detraining period and then 8 weeks of isoinertial resistance training (IRT; 4 × 7 maximal concentric-eccentric knee extensions, 3 times/week). Authors measured isometric (TMVC) and dynamic concentric (TC) knee extension torque, quadriceps anatomical cross-sectional area (ACSA), quadriceps volume, intermuscular adipose tissue (IMAT) at 50% femur length, vastus lateralis pennation angle, physiological cross-sectional area (PCSA), specific torque, and quadriceps voluntary activation (%Act) before and after each intervention.
What was found
Quadriceps volume increased significantly after both HIT and IRT (P = 0.003–0.001), and IMAT at 50% femur length decreased after both (P = 0.001–0.003). However, TMVC and TC increased significantly only after IRT (P = 0.008), with IRT eliciting a greater increase in ACSA than HIT. PCSA was significantly larger only after IRT compared to pre-training (P = 0.025), and voluntary activation improved significantly only after IRT (P = 0.011). Specific torque remained unchanged throughout the study (mean 45.5 ± 12.0 N·cm⁻²).
Why it matters
Aerobic interval training can stimulate muscle hypertrophy and decrease intermuscular fat in older adults, but resistance training is required to enhance neuromuscular activation and maximal strength.
Limits
The study had a very small sample size (n = 12) limited to healthy older men. It lacked a separate control group and utilized a fixed sequence rather than a randomized crossover design, leaving potential for carryover effects despite a 4-month detraining interval. Baseline and post-training point estimates for most morphological measures were not reported in the abstract.
Cited by
- supports In deconditioned elderly individuals, aerobic-style interval training on a stationary bike can stimulate muscle protein synthesis and increase muscle fiber size.