PMID 28932907

Research
All papers

Effects of self-paced interval and continuous training on health markers in women

Connolly LJ, Bailey SJ, Krustrup P, Fulford J, Smietanka C, Jones AM

Question

Does 12 weeks of self-paced high-intensity interval cycling improve health markers, cognition, enjoyment, and adherence in inactive premenopausal women compared with self-paced continuous cycling and an inactive control?

Summary

Inactive premenopausal women were randomized to self-paced HIIT cycling, self-paced continuous cycling, or an inactive control for 12 weeks. HIIT and continuous training both improved peak oxygen uptake, resting heart rate, and some cognitive outcomes versus control, but HIIT did so with less total work and less time commitment. HIIT did not improve fasting lipids or glucose tolerance, produced only a small body-mass reduction, and had similar final enjoyment and adherence to continuous training.

Methodology

  • Inactive premenopausal women without known metabolic or cardiovascular disease; 45 completed the trial.
  • 45 participants.
  • Indoor cycling.
  • Work intervals: Five 5-min blocks of repeated 30 s low, 20 s moderate, and 10 s high-intensity cycling.
  • Recovery: 2 min passive recovery between 5-min blocks.
  • Intensity: Low about 30%, moderate about 50-60%, high >90% maximum effort; high intervals achieved 94-95% HRpeak.
  • About 43 min including warm-up, recoveries, and cool-down; 25 min effective interval time.
  • 3 sessions/week.
  • 12 weeks.
  • Randomized controlled trial with HIIT cycling, continuous cycling, and inactive control groups; pre-post laboratory testing over 12 weeks.
  • Peak oxygen uptake, Resting heart rate and blood pressure, Body composition, and Fasting glucose and oral glucose tolerance were tracked.

Outcomes

VO2peak

VO2peak improved by 16 +/- 8% after HIIT and 21 +/- 12% after CT compared with control; absolute gains were +4.1 and +4.9 ml/kg/min.

HIIT and CT improved compared to CON, P < 0.05; group x time interaction in table for relative VO2peak P = 0.001.

Improved

Resting heart rate

Resting HR decreased by 5 +/- 9 bpm after HIIT and 4 +/- 7 bpm after CT compared with control.

P < 0.05 versus CON.

Improved

Body mass

Total body mass decreased after HIIT by 0.7 +/- 1.4 kg, while BMI, fat mass, body fat percentage, lean mass, and waist-to-hip ratio did not significantly change.

Within-group HIIT change P < 0.05; group x time for total body mass P = 0.066.

Improved

Blood pressure

Systolic BP and mean arterial pressure improved after CT but not HIIT; resting HR improved in both active groups.

CT systolic BP -5 +/- 6 mmHg and MAP -3 +/- 5 mmHg, P < 0.05.

Mixed

Glucose and lipids

Fasting serum lipids, fasting glucose, and glucose response during OGTT did not change after either training intervention.

P > 0.05.

No clear change

Cognitive function

Visual and verbal learning improved after HIIT and CT; verbal memory improved after HIIT only.

P < 0.05 for reported improvements; ISLTR interaction P = 0.053.

Mixed

Enjoyment and adherence

Post-intervention enjoyment was similar between HIIT and CT; active groups completed 35 +/- 1 sessions. HIIT had higher RPE than CT in weeks 1-8, but not weeks 9-12.

RPE group x time interaction P = 0.003; no post-intervention enjoyment difference reported.

Mixed

Insights

  • A self-paced 10-20-30 HIIT cycling protocol can improve VO2peak in inactive middle-aged premenopausal women with about half the weekly effective training time of continuous cycling.
  • Early sessions may feel harder, so a ramp-in period and self-pacing are important for tolerability.
  • This paper supports fitness and resting-heart-rate benefits more strongly than fat-loss, lipid, or glucose-control benefits.
  • Supervision, screening, and medical-clearance caveats matter when translating vigorous HIIT to previously inactive users.

Limitations

  • Small sample size with 15 completers per group.
  • Testing periods were not timed in relation to menstrual cycle.
  • The number and interaction of participants during training were not controlled.
  • Participants had generally normal baseline metabolic markers, limiting inference for people with dyslipidemia or impaired glucose control.
  • The intervention used supervised cycle ergometers, limiting direct translation to unsupervised or bodyweight formats.

Safety

  • One HIIT participant withdrew due to non-study-related lower back pain.
  • One CT participant withdrew due to non-study-related knee pain.
  • No participant dropped out of HIIT due to exercise intensity.
  • Authors advise people unaccustomed to vigorous exercise, particularly older adults, to consult a doctor before starting an exercise program.