# Effects of self-paced interval and continuous training on health markers in women PMID: 28932907 Journal: European journal of applied physiology Published: 2017 Nov Authors: 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. ## Population - Inactive premenopausal women without known metabolic or cardiovascular disease; 45 completed the trial. - Sample size: 45 - Age: HIIT 44 +/- 7 years; CT 43 +/- 7 years; CON 45 +/- 7 years - Sex: Female - Fitness level: Inactive for at least 2 years; no prior athlete or vigorous exercise participation - Health status: Premenopausal, non-smoking, not pregnant, not on medication, no known metabolic or cardiovascular disease ## Methodology - Randomized controlled trial with HIIT cycling, continuous cycling, and inactive control groups; pre-post laboratory testing over 12 weeks. - 12 weeks - University laboratory and supervised indoor cycle-ergometer training at the University of Exeter - Randomized and controlled study design. ## Protocol - Self-paced 10-20-30 HIIT cycling. - Modality: 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. - Sets or repetitions: Week 1: 3-4 x 5-min bouts; thereafter 5 x 5-min bouts. - Intensity: Low about 30%, moderate about 50-60%, high >90% maximum effort; high intervals achieved 94-95% HRpeak. - Session duration: About 43 min including warm-up, recoveries, and cool-down; 25 min effective interval time. - Frequency: 3 sessions/week. - Program length: 12 weeks. - Progression: Week 1 familiarization with lower volume; self-selected work rate increased over time. - Self-paced continuous cycling and inactive control. - Modality: Indoor cycling for CT; no exercise intervention for control. - Work intervals: CT: continuous cycling for 50 min after week 1 familiarization; control continued normal daily lives. - Recovery: No interval recovery for CT. - Sets or repetitions: CT: one continuous bout per session. - Intensity: Self-paced sustainable intensity; mean HR about 78-79% HRpeak. - Session duration: CT about 60 min including 5 min warm-up and 5 min cool-down. - Frequency: 3 sessions/week for CT. - Program length: 12 weeks. - Progression: Week 1 familiarization with 30-40 min continuous cycling; subsequent weeks 50 min; self-selected power output increased. ## Outcomes ### VO2peak Status: improved 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. ### Resting heart rate Status: improved Resting HR decreased by 5 +/- 9 bpm after HIIT and 4 +/- 7 bpm after CT compared with control. P < 0.05 versus CON. ### Body mass Status: improved 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. ### Blood pressure Status: mixed 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. ### Glucose and lipids Status: no clear change Fasting serum lipids, fasting glucose, and glucose response during OGTT did not change after either training intervention. P > 0.05. ### Cognitive function Status: mixed 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. ### Enjoyment and adherence Status: mixed 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. ## Practical 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 And Adherence - 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. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/28932907/) (pubmed) - [DOI](https://doi.org/10.1007/s00421-017-3715-9) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5640747/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.