$A_x$	anterior-posterior acceleration of the centre of mass of the whole body
C	foot impact given by optical sensors
$Cm$	mechanical cost
${\overrightarrow{D}}_i$	displacement at time i
F	resultant of external forces
$FIT$	flexible and interoperable data transfer
g	acceleration due to gravity
$GCT$	ground contact time
$GPS$	global positioning system
$GRFs$	ground reaction forces
$ICC$	Intraclass correlation coefficient
$IMU$	inertial measurement unit
$K_{leg}$	leg stiffness
L	initial leg length
$LMM$	linear mixed model
$LSS$	leg spring stiffness
m	mass of a subject
$MAS$	maximal aerobic speed
$ME$	mechanical efficiency
$PO$	power output
$RE$	running economy
${\overrightarrow{S}}_i$	speed at time i
$T_c$	contact time
$T_s$	stride time
$\dot{V}{O}_2$	oxygen consumption
$\dot{V}{O}_{2}max$	maximal oxygen consumption
${\dot{W}}_{ext}$	external mechanical power
$W_k$	kinetic work
${\dot{W}}_{met}$	metabolic power
$W_p$	potential work
$W_t$	total work
$\omega$	stride frequency