PMID 30429793

Research
All papers

High-Intensity Interval Training Improves Markers of Oxidative Metabolism in Skeletal Muscle of Individuals With Obesity and Insulin Resistance

de Matos MA, Vieira DV, Pinhal KC, Lopes JF, Dias-Peixoto MF, Pauli JR, de Castro Magalhães F, Little JP, Rocha-Vieira E, Amorim FT

Question

Does eight weeks of HIIT alter blood and skeletal-muscle markers related to insulin resistance, MAPK signaling, mitochondrial biogenesis, and oxidative metabolism in obese adults with and without insulin resistance?

Summary

In obese adults with and without insulin resistance, eight weeks of supervised cycling HIIT increased VO2peak and peak power and improved several skeletal-muscle signaling and oxidative metabolism markers. Insulin resistance by HOMA-IR improved in the insulin-resistant obese group, while fat mass did not decrease.

Methodology

  • Physically inactive adults with obesity, with and without insulin resistance; lean controls measured at baseline only.
  • 26 participants.
  • Cycle ergometer.
  • Work intervals: 60 s.
  • Recovery: 60 s active recovery at 30 W.
  • Intensity: 80-110% peak power.
  • 16-28 min including 2-min warm-up and 2-min cooldown.
  • 3 sessions/week.
  • 8 weeks.
  • Nonrandomized pre-post intervention with baseline lean control comparison
  • VO2peak, Insulin resistance, Muscle signaling, and Body composition were tracked.

Outcomes

VO2peak

VO2peak and peak power increased in both obese groups.

VO2peak and peak power p<0.0001; OB 27.2 to 30.5 and OBR 24.8 to 27.4 ml/kg/min.

Improved

HOMA-IR

Insulin-resistant obese participants improved fasting insulin, HOMA-IR, and HOMA-beta; non-insulin-resistant obese participants did not.

OBR insulin p=0.004, HOMA-IR p=0.02, HOMA-beta p=0.01; HOMA-IR 4.4 to 3.5 in Table 3.

Mixed

Muscle signaling

IRS and Akt phosphorylation increased in both obese groups.

IRS Tyr612 p=0.04; Akt Ser473 p=0.03.

Improved

Oxidative proteins

COX-IV and beta-HAD increased in skeletal muscle after HIIT.

COX-IV p=0.006; beta-HAD p=0.046.

Improved

Body fat

Fat mass did not significantly decrease; body mass, BMI, and waist circumference did not change.

No significant effect on body mass, BMI, waist circumference, or fat mass; OB body fat percentage decreased p=0.001.

No clear change

Lipids

Total cholesterol and LDL decreased overall, while HDL, VLDL, and triglycerides did not change.

Total cholesterol p=0.03; LDL p=0.03; HDL/VLDL/triglycerides p>0.05.

Mixed

Insights

  • Fitness and muscle oxidative adaptations may occur without fat loss.
  • Sixty-second intervals with equal recovery are a practical structure, but exact replication requires cycle peak-power testing.
  • Metabolic-health claims should specify screened obese adults and distinguish HOMA-IR from clamp-measured insulin sensitivity.

Limitations

  • Small sample
  • Nonrandomized groups
  • No non-exercising obese control over time
  • Surrogate muscle protein outcomes
  • No hyperinsulinemic euglycemic clamp
  • Insulin signaling measured without insulin stimulation
  • Menstrual-cycle phase not controlled
  • Limited biopsy tissue for some western blots

Safety

  • No explicit adverse-event results were reported.
  • Participants were medically screened for diabetes, glucose intolerance, chronic disease, relevant medications, and smoking.
  • HR and RPE were monitored during supervised sessions.