Prevalence of Non-responders for Glucose Control Markers after 10 Weeks of High-Intensity Interval Training in Adult Women with Higher and Lower Insulin Resistance

Álvarez C, Ramírez-Campillo R, Ramírez-Vélez R, Izquierdo M

Question

After 10 weeks of HIIT, do adult women with higher versus lower insulin resistance differ in glucose-control changes and in the prevalence of non-response for glucose, insulin, HOMA-IR, anthropometric, cardiovascular, and performance variables?

Summary

This uncontrolled intervention study assigned sedentary adult women at risk for type 2 diabetes to 10 weeks of cycling HIIT and analyzed completers as higher or lower insulin-resistance groups. Women with higher insulin resistance had significant reductions in fasting glucose, fasting insulin, and HOMA-IR, while the lower insulin-resistance group did not show significant glucose-control changes; both groups improved several skinfold and waist measures and leg-extension strength, and no injuries were reported.

Methodology

Sedentary adult women at risk for type 2 diabetes and screened for insulin resistance, analyzed as higher insulin resistance and lower insulin resistance groups after completing HIIT attendance requirements.
40 participants.
Stationary cycling on exercise bikes.
Work intervals: 60 seconds.
Recovery: Passive seated rest: 2 minutes in weeks 1-2, 1 minute 45 seconds in weeks 3-5, 1 minute 30 seconds in weeks 6-8, and 1 minute 15 seconds in weeks 9-10.
Intensity: 8-10 on modified 0-10 Borg scale; 50-70 rpm and 20-40 km/h during work intervals; described as 70%-100% maximum heart rate by Karvonen formula.
3 sessions per week.
10 weeks, 30 sessions.
Uncontrolled 10-week HIIT intervention with pre/post testing and post hoc analysis by higher versus lower insulin-resistance groups.
Fasting glucose, Fasting insulin, HOMA-IR, and Anthropometrics were tracked.

Outcomes

Glucose-control markers in H-IR

The higher insulin-resistance group significantly decreased fasting glucose by 8.8%, fasting insulin by 26.5%, and HOMA-IR by 32.1%.

Abstract reports p < 0.0001 for these changes; results section reports p <= 0.05, with high effect sizes for fasting glucose (-1.65; 95% CI -2.07 to -1.22) and HOMA-IR (-1.23; 95% CI -1.60 to -0.85).

Improved

Glucose-control markers in L-IR

The lower insulin-resistance group had no significant pre-post changes in fasting glucose, fasting insulin, or HOMA-IR.

Reported as no significant pre-post changes.

No clear change

Non-responder prevalence for fasting glucose and insulin

Non-responder prevalence was lower in H-IR than L-IR for fasting glucose and fasting insulin.

Fasting glucose: 25% vs 95%, p < 0.0001; fasting insulin: 25% vs 60%, p = 0.025.

Mixed

Non-responder prevalence for HOMA-IR

There was no significant between-group difference in non-responder prevalence for decreased HOMA-IR.

25% vs 45%, p = 0.185.

No clear change

Anthropometric measures

Both groups significantly improved waist circumference and tricipital, supra-iliac, and abdominal skinfold thicknesses; body mass and BMI changes were not significant.

Waist circumference: -5.2% H-IR, p < 0.010, and -3.8% L-IR, p = 0.046; tricipital: -13.3%, p < 0.010, and -13.6%, p < 0.0001; supra-iliac: -19.4% and -13.6%, both p < 0.0001; abdominal: -18.2%, p < 0.0001, and -15.6%, p < 0.010.

Improved

Blood pressure

Systolic blood pressure decreased significantly only in the lower insulin-resistance group; diastolic blood pressure did not change significantly in either group.

Results section reports L-IR systolic blood pressure -2.3%; abstract reports -3.2%, p < 0.010.

Mixed

Muscle performance

Both groups significantly increased 1RM leg extension, while 1RM upper row remained unchanged.

1RM leg extension: +12.9% H-IR, p < 0.010, and +14.7% L-IR, p = 0.045; L-IR 1RM leg extension effect size 1.25, 95% CI 1.04 to 1.45.

Improved

Safety/tolerability

All subjects had good exercise tolerance and none reported an injury.

Improved

Insights

This protocol used 60-second hard cycling intervals and progressed difficulty by shortening passive rest from 2 minutes to 1 minute 15 seconds.
Selected sedentary women with insulin resistance tolerated the cycling HIIT protocol with about 79%-82% compliance and no reported injuries.
Glucose-control improvements were concentrated in the higher insulin-resistance group, so baseline status matters when setting expectations.
Non-response should be anticipated and communicated, especially for individual metabolic outcomes.

Limitations

Limited sample size.
No true no-exercise control group.
Physical activity patterns and diet after training were not controlled.
Participants below 70% attendance were excluded from analyses.
The protocol used stationary cycling and may not transfer directly to bodyweight HIIT.

Safety

All subjects had good exercise tolerance.
No participant reported an injury.
Screening excluded hypertension, hypothyroidism, musculoskeletal injury, stationary asthma/respiratory disease, recent physical activity, and rural address.