PMID 31649552

Research
All papers

Effects of High-Intensity Interval Training and Isoinertial Training on Leg Extensors Muscle Function, Structure, and Intermuscular Adipose Tissue in Older Adults

Bruseghini P, Capelli C, Calabria E, Rossi AP, Tam E

Question

How do aerobic HIT and isoinertial resistance training affect quadriceps muscle function, size, architecture, activation, and intermuscular adipose tissue in healthy older men?

Summary

In 12 healthy older men, 8 weeks of supervised cycling HIT increased quadriceps muscle cross-sectional area, volume, pennation angle, and reduced intermuscular adipose tissue, but did not significantly improve maximal knee-extension torque. A later flywheel resistance block improved strength more clearly. The design had no separate control group.

Methodology

  • Moderately active healthy older Caucasian men.
  • 12 participants.
  • Cycle ergometer.
  • Work intervals: 2 min.
  • Recovery: 2 min at about 40% VO2max.
  • Intensity: 85-95% VO2max.
  • 45-50 min.
  • 3 sessions/week.
  • 8 weeks.
  • Within-subject sequential intervention study comparing HIT followed after detraining by isoinertial resistance training.
  • Quadriceps ACSA and volume, Intermuscular adipose tissue, Knee extensor torque, and Pennation angle and PCSA were tracked.

Outcomes

Quadriceps volume and ACSA

HIT and IRT both increased quadriceps ACSA and volume.

Volume HIT +42.2 cm3 p=0.003; IRT +68.2 cm3 p=0.001; ACSA increased at 25%, 50%, and 75% femur length.

Improved

IMAT

IMAT at 50% femur length decreased after HIT and IRT.

HIT p=0.001; IRT p=0.003.

Improved

Strength

Knee-extensor torque significantly increased only after IRT, not after HIT.

IRT T_MVC +11.5 Nm p=0.040; T_C +8.8 Nm p=0.008.

Mixed

Activation and PCSA

Pennation angle increased after both; PCSA and voluntary activation significantly increased only after IRT.

Activation p=0.011 after IRT; PCSA p=0.025 after IRT.

Mixed

Insights

  • Cardio-machine HIIT may improve muscle quality without producing task-specific strength gains.
  • Older-adult strength goals likely need resistance training in addition to HIIT.
  • Small uncontrolled mechanistic studies should inform hypotheses, not user-facing efficacy claims alone.

Limitations

  • No control group
  • Not randomized
  • Not counterbalanced
  • Small male-only sample
  • Healthy screened volunteers only

Safety

  • No injuries or health disorders were reported.
  • All sessions were supervised and participants were medically screened.