Table 4.

Mean vertical and fore-aft acceleration of the neck during steady-state running on a treadmill without (control) and with applied force manipulations

Force manipulation	Mean vertical acceleration (m . s−2)	Mean fore-aft acceleration (m . s−2)
Control	9.31 ± 0.96	2.27 ± 0.98a
Added head mass	9.11 ± 1.04 p = 0.30*	2.05 ± 1.16aP = 0.07*
Forward pull	–10.10 ± 1.66 p = 0.16*	–6.09 ± 1.55bP = 0.004*
Forward pull plus added head mass	–9.58 ± 1.45 p = 0.10**	–5.75 ± 1.98bP = 0.73**
Rearward pull	9.58 ± 1.79 p = 0.73*	6.65 ± 2.36bP = 0.004*
Rearward pull plus added head mass	8.88 ± 1.56 p = 0.004***	5.67 ± 1.92bP = 0.07***
Comparison of mean acceleration during forward and rearward trials	p = 0.30	P = 0.50

^* P-value calculated relative to control trials.

^** P-value calculated relative to forward pull trials.

^*** P -value calculated relative to rearward pull trials.

^aAverage during accelerating portion (second half) of the step.

^bAverage during the entire step.