Variable intensity interval training improves cardiorespiratory fitness and quality of life across Hashimoto's stages and lowers TSH in subclinical patients: a 12-week supervised study.

PURPOSE: This study aimed to evaluate the effects of variable intensity interval training (VIIT) on thyroid function, body composition, cardiorespiratory fitness, and quality of life (QoL) in women with Hashimoto's thyroiditis (HT) at different stages of disease progression.

METHODS

Thirty-one women (aged 18-65) with confirmed Hashimoto's thyroiditis were assigned to three groups: euthyroid (n = 10), subclinical (n = 11), and clinical (n = 10). The 12-week supervised intervention consisted of VIIT combining higher and moderate-intensity intervals. Markers of thyroid function and autoimmunity were assessed via blood analysis. Body composition was measured by bioelectrical impedance, cardiorespiratory fitness by a graded exercise test on a cycle ergometer, and quality of life using the SF-36 questionnaire. Intervention effects were evaluated using a two-factor repeated-measures ANOVA (time × group).

RESULTS

The subclinical HT group showed a significant reduction in thyroid-stimulating hormone (TSH; -32%, p < 0.01; Cohen's d = 1.03), while no hormonal or antibody changes were observed in the other groups. Both the subclinical and clinical groups showed significant reductions in body mass and BMI (p < 0.05), whereas body fat percentage decreased only in the subclinical group. All groups demonstrated a significant increase in maximal oxygen uptake (VO₂max; 13-22%, p < 0.05). Improvements in several quality-of-life domains were observed following the intervention, particularly in the subclinical and clinical groups (p < 0.05).

CONCLUSION

VIIT may advance thyroid function in women with subclinical HT and improve cardiorespiratory fitness, body composition and QoL across all stages of the disease.