Preliminary Investigations Into the Effect of Exercise-Induced Muscle Damage on Systemic Extracellular Vesicle Release in Trained Younger and Older Men

Figures

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  Figure 1. Schematic of experimental procedures. BIA, body impedance analysis; CK, creatine kinase; MVIC, maximal voluntary isometric contraction for peak force; DOMS, delayed onset muscle soreness via visual analogue scale; RM, repetition maximum; and EIMD, exercise-induced muscle damage. Second visit combines both pre- and post-measurements, immediately prior and following EIMD stimulus, respectively.

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  Figure 2. Measurement of EV modal size and count in younger and older participants. (A) Representative example of nanoparticle tracking analysis (NTA), SEM shown in red and mean in black line. (B) Western blotting of human plasma extracellular vesicles (EVs) showing positive for Flot-1 and CD63. (C) Transmission electron microscopy (TEM) images of human plasma-EVs, showing EV morphology; scale bar indicates 100nm. (D) EV modal size (nm) and (E) EV count (particles/ml) at pre-EIMD in younger (open circles) and older (closed circles) participants. Horizontal line indicates group means.

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  Figure 3. Exercise-induced muscle damage reduces muscle force and increases circulating creatine kinase (CK) concentrations independent of age. (A) MVIC (kg), (B) DOMS [0–10 visual analogue scale (VAS)], and (C) plasma CK (U/L) of younger (open circles) and older (closed circles) participants. Red shaded zones indicate SEM in (A,C), and interquartile range in (B), and black connected line indicates group means in (A,C), and medians in (B), values of p between timepoints as indicated. The scale brake indicates from hourly testing to 24-h intervals.

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  Figure 4. Alterations in EV modal size and count with exercise, and EV correlations with muscle damage markers. (A) EV modal size (% pre-EIMD) and (B) EV count (% pre-EIMD) as a function of timepoint between younger and older groups, (C) EV modal size (% pre-EIMD) and (D) EV count (% pre-EIMD) as a function of timepoint combined younger and older participants (n=12). Red shaded zones indicate SEM and black connected line indicates group means. The scale brake indicates from hourly testing to 24-h intervals. (E) Correlation matrix between change in EV modal size (ΔMode) or in EV count (ΔCount) as a function of CK (U/L), (F) as a function of MVIC (kg) and (G) as a function of DOMS (0–10 VAS) at each timepoint measured, with r values as shown. *Indicates significant association between variables (each p<0.05). Colour intensity for r values (purple indicates positive r value, green negative, white=0) as indicated. (H) CK (U/L) at 72h as a function of ΔMode (post-EIMD – pre-EIMD and I) CK (U/L) at 48h as a function of ΔCount (post-EIMD – pre-EIMD). Red shaded zone indicates 95% CIs. Open circles indicate younger, closed indicate older.