Table 1.

Characteristics of included studies comparing oral contraceptive pill (OCP) users and OCP non-users following matched resistance exercise training interventions

Study	n	Training status	Intervention duration (weeks)	Supervised training	Outcomes	Results OCP versus non-users	Study conclusion	Methodological quality score
Dalgaard et al., 2019 [20]	OCP-users: 14 Naturally menstruating: 14	Untrained	10	Yes	Hypertrophy:		Use of OCPs was associated with a trend towards a greater increase in muscle mass and a significantly greater increase in type I muscle fibre area compared with controls. Use of OCPs did not influence the overall increase in muscle strength related to training	12
					MRI:
					Vastus lateralis muscle CSA	↔
					Biopsy:
					Vastus lateralis type I fibre CSA	↑
					Vastus lateralis type II fibre CSA	↔
					Strength:
					1RM:
					Knee extension	↔
					Isokinetic dynamometer IMVC:
					Knee extension	↔
Dalgaard et al., 2022* [19]	OCP-users: 20 Naturally menstruating: 18	Untrained	10	Yes	Hypertrophy:		The use of a second-generation OCP in young untrained women does not promote significantly greater gains in muscle mass or muscle strength compared with non-users	13
					DXA
					Fat-free mass	↔
					MRI:
					Vastus lateralis muscle CSA (10 cm)	↔
					Vastus lateralis muscle CSA (20 cm)	↔
					Vastus lateralis muscle CSA (30 cm)	↔
					Biopsy:
					Vastus lateralis type I fibre CSA	↔
					Vastus lateralis type II fibre CSA	↔
					Power:
					Counter-movement jump	↔
					Strength:
					5RM:
					Leg press	↔
					Isokinetic dynamometer IMVC:
					Knee extension	↔
					Knee flexion	↔
Nichols et al., 2008 [22]	OCP-users: 13 Naturally menstruating: 18	Trained (NCAA Division 1 Collegiate Athletes)	12	NR	Strength:		The use of OCPs did not provide sufficient androgenic effect to increase strength gains beyond the stimulus of the training protocol	6
					1RM:
					Bench press	↔
					10RM:
					Knee extension	↔
					Isokinetic dynamometer peak torque:
					Bench press	↔
					Knee extension	↔
Oxfeldt et al., 2020* [15]	OCP-users: 20 Naturally menstruating: 18	Untrained	10	Yes	Hypertrophy:		Use of second-generation OCPs in young untrained women increased skeletal muscle MRF4 expression and satellite cell number compared with non-users	13
					Biopsy:
					Vastus lateralis type I fibre CSA	↔
					Vastus lateralis type II fibre CSA	↔
Reichmann and Lee, 2021 [16]	OCP-users: 34 Naturally menstruating: 38	Untrained	10	Yes	Hypertrophy:		OC use impairs muscle gains in young healthy untrained women, but the effect may depend on the type of OCPs	9
					Hydrostatic weighing:
					Lean mass	↓
					Strength:
					1RM:
					Arm strength (aggregated score)	↔
					Leg strength (aggregated score)	↔
Romance et al., 2019 [23]	OCP-users: 12 Naturally menstruating: 11	Trained (> 2 years’ continuous resistance exercise training)	8	Yes	Hypertrophy:		OC use does not impair strength gains nor body composition in resistance-trained young adult women	9
					DXA:
					Fat-free mass	↔
					Power:
					Counter-movement jump	↔
					Strength:
					1RM:
					Bench press	↔
					Squat	↔
Sung et al., 2022 [24]	OCP-users: 34 Naturally menstruating: 40	Untrained	12	Yes	Hypertrophy:		The effects of RET on muscle strength, muscle thickness, muscle fibre size and composition were similar in young women irrespective of their OCP use	8
					Ultrasound:
					Muscle thickness (sum of rectus femoris, vastus lateralis and vastus Intermedius)	↔
					Biopsy:
					Vastus lateralis type I fibre muscle Thickness	↔
					Vastus lateralis type II fibre muscle thickness	↔
					Strength:
					Combined force and load cell IMVC:
					Leg press	↔
Wikstrom-Frisen et al., 2017 [25]	Group 1: OCP-users: 11 Naturally menstruating: 8 Group 2: OCP-users: 10 Naturally menstruating: 9 Group 3: OCP-users: 11 Naturally menstruating: 10	Trained (Mean resistance exercise training experience of 3.5 years)	16	Yes	Hypertrophy:		High-frequency periodised leg resistance training during the first 2 weeks of the menstrual/OCP cycle was more beneficial in terms of power gain, strength gain and increased leg lean mass compared with high-frequency resistance training during the last 2 weeks	5
					DXA:
					Leg lean mass	↔
					Whole body lean mass	↔
					Power:
					Counter-movement jump	↔
					Squat jump	↔
					Strength:
					Isokinetic dynamometer peak torque:
					Single-leg knee extension (right and left)	↔
					Single-leg knee flexion (right and left)	↔

CSA cross-sectional area, DXA dual-energy X-ray absorptiometry, IMVC isometric maximal voluntary contraction, MRI magnetic resonance imaging, NCAA National Collegiate Athletic Association, OCP oral contraceptive pill, RM repetition maximum

↑ = significant difference favouring OCP group; ↔  = No significant difference between groups; ↓ = significant difference favouring OCP non-users group

*Shared participants