Table 4. GRFs in pivot and stride leg difference between adolescent and collegiate pitchers. Values are expressed as mean (±SD). Variable Adolescent pitcher (n = 32) Collegiate pitcher (n = 30) ES Adolescent pitcher (n = 32) Collegiate pitcher (n = 30) ES GRFs Force Fx Force Fz Force on pivot leg at MKH (N/kg) -.2 (.3) -.3 (.3) .14 8.0 (1.5) 6.8 (1.8)** .69 Force on pivot leg at MAP (N/kg) -.3 (.7) -.3 (.7) .08 10.5 (1.9) 10.8 (2.4) .16 Force on stride leg at MER (N/kg) .6 (.9) .4 (1.0) .28 18.4 (1.8) 18.4 (1.7) .00 Force on stride leg at REL (N/kg) .9 (.7) 1.2 (.9) .39 16.6 (2.5) 17.7 (2.2) .47 Force Fy Resultant forces Force on pivot leg at MKH (N/kg) .7 (.4) .8 (.5) .25 8.1 (1.5) 7.0 (1.7)** .69 Force on pivot leg at MAP (N/kg) 7.2 (1.3) 8.4 (1.7)** .74 12.8 (2.2) 13.8 (2.7) .40 Force on stride leg at MER (N/kg) -10.2 (1.6) -10.9 (1.7) .43 21.1 (2.1) 21.5 (2.1) .16 Force on stride leg at REL (N/kg) -7.9 (2.0) -9.3 (1.8)** .70 18.4 (3.0) 20.1 (2.6)* .57 Maxima and minima of GRFs Pivot leg Stride leg Maximum Fx (N/kg) 1.4 (.6) 1.3 (.6) .18 1.2 1.4 (.7) .23 Maximum Fy (N/kg) 7.2 (1.3) 8.4 (1.7) ** .74 Maximum Fz (N/kg) 12.5 (1.7) 12.9 (2.1) .23 19.5 (2.0) 19.2 (1.7) .16 Maximum Resultant forces (N/kg) 14.0 (2.2) 14.9 (2.6) .37 22.2 (2.5) 22.2 (2.0) .03 Minimum Fx (N/kg) -.7 (.5) -.7 (.5) .06 -1.3 (.8) -1.1 (.7) .22 Minimum Fy (N/kg) -10.9 (1.8) -11.1 (1.7) .11 ES; Effect Size value. MKH; Maximal stride knee height. MAP; Maximal anterior push-off force. SFC; Stride foot contacts ground. MER; Maximum shoulder external rotation. REL; Ball release. * p < 0.05, Significant difference between adolescent and collegiate pitchers. ** p < 0.01, Significant difference between adolescent and collegiate pitchers