Comparison of the cytokine responses to acute strength exercise between oral contraceptive users and naturally cycling women

Abstract

Purpose: Cytokines are released as part of an inflammatory reaction in response to strength exercise to initiate muscle repair and morphological adaptations. Whether hormonal fluctuations induced by the menstrual cycle or oral contraceptives affect inflammatory responses to strength exercise remains unknown. Therefore, we aimed to compare the response of cytokines after acute strength exercise in naturally menstruating women and oral contraceptive users.

Methods: Naturally menstruating women (MC, n = 13, 24 ± 4 years, weekly strength training: 4.3 ± 1.7 h) and women using a monophasic combined pill (> 9 months) (OC, n = 8, 22 ± 3 years, weekly strength training: 4.5 ± 1.9 h) were recruited. A one-repetition-maximum (1RM) test and strength exercise in the squat (4 × 10 repetitions, 70%1RM) was performed in the early follicular phase or pill free interval. Concentrations of oestradiol, IL-1β, IL-1ra, IL-6, IL-8, and IL-10 were assessed before (pre), directly after (post) and 24 h after (post₂₄) strength exercise.

Results: IL-1ra increased from pre to post (+ 51.1 ± 59.4%, p = 0.189) and statistically decreased from post to post₂₄ (- 20.5 ± 13.5%, p = 0.011) only in OC. Additionally, IL-1β statistically decreased from post to post₂₄ (- 39.6 ± 23.0%, p = 0.044) only in OC. There was an interaction effect for IL-1β (p = 0.038) and concentrations were statistically decreased at post₂₄ in OC compared to MC (p = 0.05). IL-8 increased across both groups from post to post₂₄ (+ 66.6 ± 96.3%, p = 0.004).

Conclusion: We showed a differential regulation of IL-1β and IL-1ra between OC users in the pill-free interval and naturally cycling women 24 h after strength exercise, while there was no effect on other cytokines. Whether this is associated with previously shown compromised morphological adaptations remains to be investigated.

Keywords: Follicular phase; Hormonal contraception; Interleukin-1; Interleukin-8; Menstrual cycle.

Fig. 1

Timing of testing in the natural menstrual cycle and oral contraceptive intake (exemplary data modified from Sims and Heather (2018). Testing was performed in the early follicular phase or pill-free interval of the respective cycle. 1RM = one-repetition maximum in the back squat

Fig. 2

Baseline concentrations at pre of all cytokines (A) and fold change from baseline values for IL-1β (B), IL-1ra (C), IL-6 (D), IL-8 (E) and IL-10 (F). For IL-1β analysis was performed for n = 20 (MC: 13, OC: 7) and for IL-6 n = 19 (MC:11, OC: 8). Data are shown as mean ± SD, with black dots showing individual values