Contractile Properties of Single Muscle Fiber and Their Relations to Whole Muscle Strength in Korean Young Male

Abstract

PURPOSE This study investigated the muscle fiber type-related contractile properties and examined the relationship between whole limb muscle strengths and single muscle fiber contractile properties in Korean men. METHODS Six Korean men (29.8±1.49 yr) were recruited and participated in the study. Samples were obtained from vastus lateralis muscles. CSA, Po, SF, Vo of single fiber segments were measured using an isometric force transducer and a high-speed motor. Silver staining was performed to identify MHC isoform composition of single muscle fiber segments. Multiple regression was tested to identify the relationship between single muscle fiber contractile properties and whole muscle strength. RESULTS MHC isoforms were distributed in different proportion (Type I: 57.3%, IIa: 34.2%, IIa/IIx: 4.3%, IIx: 4.3%). CSA of type IIx were smaller compared to type I (-50%) and type IIa (-57.5%). Po in type IIa was 12.9% higher compared to type I (p<.05). While SF in type IIa were 7.7% higher than type I, type IIx were higher than type I, IIa, IIa/IIx (31.4%, 25.7%, 30.9%). Vo increased in the order type I<IIa<IIa/IIx<IIx. There was positive correlation between single fiber and properties (Po vs. thigh strength: r2=.248, Po vs. thigh power: r2=.058, Vo vs. thigh power: r2=.095). CONCLUSIONS These results suggest that single muscle fiber contractile properties were exclusively dependent on fiber type isoforms, ruling out a possibility of race-induced difference in fiber type-matched contractile properties.

Keywords

• korean men
• single muscle fiber
• whole muscle strength
• mhc isoform
• hybrid fiber