Estrogen Source Influences Muscle Soreness and Recovery in Young Women

Abstract

Methods100 contractions of maximally tolerated neuromuscular electrical stimulation (NMES) were performed on one quadriceps. The oral contraceptive (OC) group, consuming an exogenous estrogen source, performed NMES between days 8‐11 of pill consumption. The high (HI) and low (LO) endogenous estrogen groups performed NMES between days 19‐21 or 1‐3 of the menstrual cycle, respectively; day 1 was menses onset. HI and LO did not take OC. Maximal voluntary isometric contraction (MVIC) was assessed before, 0, and 48 hours post. Soreness was measured before and 48 hours post with a 7‐point and 10‐point Likert Scale of Muscle Soreness for Lower Limb (LSMSLL) and a 100 mm visual analog scale (VAS). Maximum and average Rating of Perceived Exertion (RPE) and Pain were reported for the NMES bout.ResultsMean maximum (15.9) and average (13.8) RPE were similar across groups. HI reported 2‐3 points lower mean maximum and average Pain than OC or LO. OC (N=5) HI (N=2) LO (N=2) Age (years) 25 (3) 25 (1) 27 (3) BMI (kg/m2) 23.2 (1.4) 22.6 (4.7) 24.1 (3.8) Body Weight (kg) 63.9 (5.3) 58.1 (12.0) 65.5 (7.4) Lean Mass (kg) 45.9 (3.4) 41.7 (3.6) 41.3 (2.8) Percent Fat 27.8 (5.9) 27.4 (8.7) 32.2 (17.3) NMES MVIC (N) 335.4 (49.6) 355.5 (41.0) 263.1 (96.1) %MVIC (avg NMES force) 34.2 (7.7) 44.8 (3.6) 43.3 (26.0) %MVIC (0 hrs post) 86.4 (18.3) 82.7 (4.6) 71.4 (3.2) %MVIC (48 hrs post) 97.4 (7.6) 86.4 (11.0) 91.1 (40.4) Soreness Delta_VAS (mm) 380.5 (196.4) 587.5 (116.7) 375.0 (176.8) Delta_7 pt 2.8 (0.8) 4.0 (0.7) 3.8 (1.1) Delta_10 pt 4.2 (1.9) 5.8 (1.8) 6.0 (2.8) ConclusionThese results are interpreted with the knowledge that this is an ongoing study with recruitment goals of N=7 per group. Given the current small sample size and large variability, exogenous estrogen may increase exertion perception as OC did less work and experienced less soreness and faster recovery than HI and LO despite higher lean mass and similar exertion rating. Either source of estrogen may decrease immediate post‐exercise fatigue as LO displayed a greater degree of strength loss at 0 hours post NMES despite doing similar work to HI and more work than OC. Future analysis requires covarying for absolute force and lean mass.