Effects of 8 Weeks of Moderate- or High-Volume Strength Training on Sarcoplasmic Reticulum Ca2+ Handling in Elite Female and Male Rowers

Abstract

While acute exercise affects sarcoplasmic reticulum (SR) function, the impact of resistance training remains unclear. The purpose of the present study was to investigate SR Ca²⁺ handling plasticity in response to moderate- and high-volume strength training in elite rowers. Twenty elite male (n = 12) and female (n = 8) rowers performed three weekly strength training sessions for 8 weeks and were randomly allocated to either perform 3 sets (3-SET) or progressive increase from 5 to 10 sets (10-SET) of 10 repetitions during the training period. Skeletal muscle biopsies were collected before and after the intervention period and analyzed for SR vesicle Ca²⁺ handling, SR related proteins, and myosin heavy chain (MHC) composition. Muscle strength was determined by isometric midthigh pull (IMTP). Training increased both the overall SR Ca²⁺ release (19%) and uptake rates (34%), with no differences between groups. SR protein analysis revealed a high variability but suggests an increase of RYR1 and SERCA1, while SERCA2 decreased, corroborating changes in SR function, with no differences between groups. Regardless of training volume, a 9% higher relative MHCIIa proportion and a 7% decrease in the MHCI isoform was observed. There was an overall 8% increase of IMTP. Males exhibited higher SR Ca²⁺ uptake and release rates compared to females, likely explained by a higher proportion of MHCII. These findings suggest that 8 weeks of moderate- or high-volume strength training enhances SR vesicle Ca²⁺ uptake and release rates in elite male and female rowers, accompanied by a shift toward a larger proportion of MHCIIa fiber type.

Keywords: Ca2+ release; Ca2+ uptake; muscle plasticity; sex difference; strength training.

FIGURE 1

Effects of 8 weeks of strength training on SR vesicle Ca²⁺ uptake and release rates. Changes in SR vesicle Ca²⁺ uptake, estimated as (A) Tau⁻¹, i.e., reciprocal time for free [Ca²⁺] to decrease by 63%, with increased value denoting higher uptake rate (B) uptake rate at 600 nM Ca²⁺, (C) uptake rate at 200 nM Ca²⁺ and (D) changes in SR vesicle Ca²⁺ release rate, following 8 weeks of either high‐volume strength training (10‐SET) or moderate‐volume (3‐SET). Data are presented as means and individual paired values. n = 8 for 10‐SET and 9 for 3‐SET, except for uptake low 3‐SET (n = 8).

FIGURE 2

Effects of 8 weeks of strength training on SR Ca²⁺ related proteins. Changes in m. vastus lateralis content of (A) sarcoplasmic reticulum Ca²⁺‐ATPase 2, (B) sarcoplasmic reticulum Ca²⁺‐ATPase 1, and (C) ryanodine receptor 1 following 8 weeks of either high‐volume strength training with 5–10 sets of 10 repetitions (10‐SET, n = 6): Or moderate‐volume with 3 sets of 10 repetitions (3‐SET, n = 7). Data are presented as means and individual paired values Immunoblotting of the SR proteins was conducted on 6 (10‐st) and 7 (3‐SET) paired pre‐ and post‐training. (D) Representative bands of SERCA2, SERCA1, and RyR1.

FIGURE 3

SR vesicle Ca²⁺ uptake and release rates in male and females. Individual and mean values of (A) Tau⁻¹, i.e. reciprocal time for free [Ca²⁺] to decrease by 63%, with increased value denoting higher uptake rate (B) uptake rate at 600 nM Ca²⁺, (C) uptake rate at 200 nM Ca²⁺, and (D) SR vesicle Ca²⁺ release rate in elite male (n = 10–11) and female (n = 6–7) rowers. Data are presented as means and individual values.

FIGURE 4

SR Ca²⁺ related proteins male and females. Individual and mean values of (A) SERCA2, (B) SERCA1, and (C) RyR1 in m. vastus lateralis of elite male (n = 9) and female (n = 5) rowers. Data are presented as means and individual values. (D) Representative bands of SERCA2, SERCA1, and RyR1 in male and female.