It was hypothesized that certain ground reaction force (GRF) variables are positively correlated with running economy (RE; the aerobic demand at a single speed of running). Excessive momentum changes, quantified by linear impulse measures, as well the free moment applied to the running surface could be considered potentially wasteful efforts in terms of metabolic energy requirements. Recreational runners (n = 16) ran on a treadmill at 3.35 m.s-1 for physiological measurements and overground for biomechanical measurements. Correlation coefficients were calculated between RE and total vertical impulse (TVI), net impulses in three orthogonal directions, and descriptors of the free moment. The TVI and the net vertical impulse were the only GRF characteristics significantly correlated to RE (r = 0.62, r = 0.60, respectively). Greater overall muscle support requirements during ground contact, as represented by TVI, may have been responsible for greater aerobic demand.

The inverse relationship between Kvert and aerobic demand indicates that less economical runners possess a more compliant running style during ground contact. This running style may place greater force demands on extensor musculature.

The purpose of this study was to investigate the influence of weight distribution (WtD) asymmetry on the biomechanics of a barbell back squat. This study included 2 groups of trained individuals who were separated based on a WtD test (n = 14 in each group). They performed the barbell back squats with 2 resistance levels (60 and 75% of 1 repetition maximum) to measure vertical ground reaction force (GRF), tilting, and rotational angular bar displacements. A symmetry index (SI) score of the vertical GRF and the 2 bar displacements were examined to identify the group difference. Results showed that the unequal WtD group displayed a higher vertical GRF SI score (p < 0.05) and greater degrees of the tilting (p < 0.05) and rotational (p < 0.05) angular bar displacements. The 2 resistances did not influence the magnitude of the dependent variables, and no interactions were found. The unequal WtD captured at the WtD test carried over to the SI score during the back squat test. The unequal WtD was also a partial factor of displaying greater bar displacements. The lack of postural control to distribute body weight evenly should be treated properly to gain levelness before participating in high volume of resistance training, and coaches should be conscious of moving in a symmetrical fashion with minimal bar displacements in tilting and rotational manner.