Position -specific Differences in Maximal Voluntary Contraction and Rate of Force Development in Collegiate American Football Players

The ability to rapidly generate a high force is essential for sports performance. Rate of force development (RFD), which reflects the rate of force increase during explosive movements, is important in athletics. This study examined the relationship between maximal voluntary contraction (MVC) and RFD during isometric knee extension and flexion in American collegiate football players, considering position-specific differences.The participants were 25 collegiate American football players (backs; n = 15, linemen; n = 10). Isometric knee extension and flexion were measured using a Biodex dynamometer under the MVC and RFD conditions. RFD was calculated as the slope of the linear regression line from force onset to the breakpoint, which was defined as the time point at which the smallest difference in 30-ms force increments occurred within 270-ms. The MVC and RFD values were normalized to skeletal muscle mass (SMM) and expressed as MVC/SMM and RFD/SMM, respectively.Linemen exhibited higher absolute MVC values for both knee extension (linemen; 185.9 ± 37.6 Nm, backs; 164.6 ± 34.7 Nm) and flexion (linemen; 103.2 ± 23.4 Nm, backs; 99.7 ± 19.1 Nm). However, MVC/SMM was higher in backs (extension; 3.1 ± 0.68 Nm·kg⁻¹, flexion; 1.9 ± 0.38 Nm·kg⁻¹) than in linemen (extension; 3.0 ± 0.5 Nm·kg⁻¹, flexion; 1.7 ± 0.37 Nm·kg⁻¹). RFD was greater in linemen (extension; 1085.3±310.4 Nm·s⁻¹, flexion; 745.6±177.7 Nm·s⁻¹) than in backs (extension; 1022.5±236.9 Nm·s⁻¹, flexion; 662.7±184.9 Nm·s⁻¹). However, RFD/SMM was higher in backs (extension; 19.4±4.4 Nm·kg⁻¹·s⁻¹, flexion; 12.6±3.4 Nm·kg⁻¹·s⁻¹) than in linemen (extension; 18.2±6.3 Nm·kg⁻¹·s⁻¹, flexion; 12.4±3.5 Nm·kg⁻¹·s⁻¹). Linemen exhibited a greater absolute MVC and RFD, indicating the importance of maximal force generation for blocking tasks. Contrastingly, backs demonstrated higher normalized values, suggesting a reliance on efficient force production per unit of muscle mass for agility and rapid movements. These findings underscore the position-specific muscular demands of American football players.