High-intensity interval training (HIIT) was better than moderate-intensity continuous training (MICT) for improving several measures of cardiometabolic health in women with polycystic ovary syndrome (PCOS) in a prospective, randomized, single-center study with 27 women.
After 12 weeks on a supervised exercise regimen, the women with PCOS who followed the HIIT program had significantly better improvements in aerobic capacity, insulin sensitivity, and level of sex hormone–binding globulin, Rhiannon K. Patten, MSc, said at the annual meeting of the Endocrine Society.
“HIIT can offer superior improvements in health outcomes, and should be considered as an effective tool to reduce cardiometabolic risk in women with PCOS,” concluded Patten, a researcher in the Institute for Health and Sport at Victoria University in Melbourne in her presentation (Abstract OR10-1).
“The changes we see [after 12 weeks on the HIIT regimen] seem to occur despite no change in body mass index, so rather than focus on weight loss we encourage participants to focus on the health improvements that seem to be greater with HIIT. We actively encourage the HIIT protocol right now,” she said.
Both regimens use a stationary cycle ergometer. In the HIIT protocol patients twice weekly pedal through 12 1-minute intervals at a heart rate of 90%-100% maximum, interspersed with 1 minute rest intervals. On a third day per week, patients pedal to a heart rate of 90%-95% maximum for 6-8 intervals maintained for 2 minutes and interspersed with rest intervals of 2 minutes. The MICT regimen used as a comparator has participants pedal to 60%-70% of their maximum heart rate continuously for 50 minutes 3 days weekly.
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HIIT Saves Time
“These findings are relevant to clinical practice, because they demonstrate that HIIT is effective in women with PCOS. Reducing the time devoted to exercise to achieve fitness goals is attractive to patients. The reduced time to achieve training benefits with HIIT should improve patient compliance,” commented Andrea Dunaif, MD, professor and chief of the division of endocrinology, diabetes, and bone disease of the Mount Sinai Health System in New York, who was not involved with the study.
The overall weekly exercise time on the MICT regimen, 150 minutes, halves down to 75 minutes a week in the HIIT program. Guideline recommendations released in 2018 by the International PCOS Network recommended these as acceptable alternative exercise strategies. Patten and her associates sought to determine whether one strategy surpassed the other, the first time this has been examined in women with PCOS, she said.
They randomized 27 sedentary women 18-45 years old with a body mass index (BMI) above 25 kg/m2 and diagnosed with PCOS by the Rotterdam criteria to a 12-week supervised exercise program on either the HIIT or MICT protocol. Their average BMI at entry was 36-37 kg/m2. The study excluded women who smoked, were pregnant, had an illness or injury that would prevent exercise, or were on an oral contraceptive or insulin-sensitizing medication.
At the end of 12 weeks, neither group had a significant change in average weight or BMI, and waist circumference dropped by an average of just over 2 cm in both treatment groups. Lean mass increased by a mean 1 kg in the HIIT group, a significant change, compared with a nonsignificant 0.3 kg average increase in the MICT group.
Increased Aerobic Capacity ‘ Partially Explains ‘ Improved Insulin Sensitivity
Aerobic capacity, measured as peak oxygen consumption (VO2peak), increased by an average 5.7 mL/kg per min among the HIIT patients, significantly more than the mean 3.2 mL/kg per min increase among those in the MICT program.
The insulin sensitivity index rose by a significant, relative 35% among the HIIT patients, but barely budged in the MICT group. Fasting glucose fell significantly and the glucose infusion rate increased significantly among the women who performed HIIT, but again showed little change among those doing MICT.
Analysis showed a significant link between the increase in VO2peak and the increase in insulin sensitivity among the women engaged in HIIT, Patten reported. The improvement in the insulin sensitivity index was “partially explained” by the increase in VO2peak, she said.
Assessment of hormone levels showed a significant increase in sex hormone–binding globulin in the HIIT patients while those in the MICT group showed a small decline in this level. The free androgen index fell by a relative 39% on average in the HIIT group, a significant drop, but decreased by a much smaller and not significant amount among the women who did MICT. The women who performed HIIT also showed a significant drop in their free testosterone level, a change not seen with MICT.
Women who performed the HIIT protocol also had a significant improvement in their menstrual cyclicity, and significant improvements in depression, stress, and anxiety, Ms Patten reported. She next plans to do longer follow-up on study participants, out to 6 and 12 months after the end of the exercise protocol.
“Overall, the findings suggest that HIIT is superior to MICT for improving fitness and insulin sensitivity in the short term. Results from a number of studies in individuals without PCOS suggest that HIIT is superior to MICT for improving fitness short term,” commented Dunaif. “This study makes an important contribution by directly investigating the impact of training intensity in women with PCOS. Larger studies will be needed before the superiority of HIIT is established for women with PCOS, and study durations of at least several months will be needed to assess the impact on reproductive outcomes such as ovulation,” she said in an interview. She also called for assessing the effects of HIIT in more diverse populations of women with PCOS.
Patten had no disclosures. Dunaif has been a consultant to Equator Therapeutics, Fractyl Laboratories, and Globe Life Sciences.