Uphill sprinting load– and force–velocity profiling: Assessment and potential applications

Figures & data

Table 1. Definition and practical interpretation of the main variables of interest when using force–velocity–power profiling in sprinting (adapted with permission, (Samozino et al., 2016))

Profiling Variable	Definition and Computation
F0 (N·kg^−1)	Theoretical maximal horizontal force production as extrapolated from the linear sprint FV relationship; y-intercept of the linear FV relationship.
V0 (m·s^−1)	Theoretical maximal running velocity as extrapolated from the linear sprint FV relationship; x–intercept of the linear FV relationship.
Pmax (W.kg^−1)	Maximal mechanical power output in the horizontal direction, computed as Pmax = F0 × V0/4, or as the apex of the PV 2nd-degree polynomial relationship.
FVslope	Index of the athlete’s individual balance between force and velocity capabilities. The steeper the slope, the more negative its value, the more “force-oriented” the FV profile, and vice versa.
RF (%)	Direct measurement of the proportion of the total force production that is directed in the forward direction of motion, i.e., the mechanical effectiveness of force application of the athlete. The higher the value, the more important the part of the total force output directed forward.
RFmax (%)	Maximal value of RF, computed as maximal value of RF for sprint times >0.3 s.
DRF	Rate of decrease in RF with increasing velocity during sprint acceleration, computed as the slope of the linear RF–V relationship.

Table 2. Descriptive statistics (mean ± SD) for individual force–velocity–power (FVP) and load–velocity (LV) profiles for collegiate level athletes

Profile	Variable	Male (n = 10)	Female (n = 14)	Pooled (n = 24)
FVP	Maximal Velocity (m·s^−1)	8.43 ± 0.67	7.46 ± 0.46	7.81 ± 0.75
	V0 (m·s^−1)	8.78 ± 0.75	7.74 ± 0.52	8.12 ± 0.83
	FVslope (N·kg^−1/m·s^−1)	−0.82 ± 0.11	−0.84 ± 0.1	−0.83 ± 0.1
	F0 (N·kg^−1)	7.2 ± 0.97	6.47 ± 0.58	6.74 ± 0.83
	Pmax (W.kg^−1)	15.9 ± 2.8	12.5 ± 1.3	13.8 ± 2.7
	RFmax (%)	43.2 ± 3.6	39.3 ± 1.8	40.7 ± 3.3
	DRF (%)	−7.7 ± 1	−8 ± 0.9	−7.9 ± 0.9
LV	L0 (%)	73.9 ± 3.7	67.6 ± 3.4	70.2 ± 4.7
	LVslope (m·s^−1/%)	−0.11 ± 0.01	−0.11 ± 0.01	−0.11 ± 0.01
	L @ Vopt (%)	36.9 ± 1.9	33.8 ± 1.7	35.1 ± 2.3

V0 = maximal theoretical velocity; FVslope = slope of the force-velocity relationship; F0 = maximal theoretical force; P_max = maximal theoretical relative power; RF_max = maximal ratio of force horizontal:vertical force; DRF = decrease in ratio of force, L0 = maximal theoretical load at zero velocity; LVslope = slope of the load-velocity relationship; L @ Vopt = load at optimum velocity.

Figure 1. Load–velocity profile during hill sprinting of collegiate-level athletes. Trendline represents the average profile (± SD) for males (n = 10) and females (n = 14), respectively.

Figure 2. Example of one athlete’s force–velocity–power profile measured during sprint on flat terrain (trendlines representing force–velocity and power–velocity relationships, respectively). Points on each line represent the velocity achieved during the flat sprint and each of the three different hill conditions, demonstrating that the gradients assessed during this study represented the velocity end of the force–velocity relationship.

Table 3. Reliability statistics (± 90% confidence intervals) for individual load–velocity measures during hill sprinting for collegiate level athletes

Variable	Trial 1	Trial 2	TE	TE (%)
V @ 0%	8.15 ± 0.74	8.03 ± 0.79	0.13; 0.09 to 0.22	1.8; 1.3 to 3.1%
V @ 5.2%	7.50 ± 0.72	7.37 ± 0.70	0.09; 0.07 to 0.16	1.3; 0.9 to 2.2%
V @ 8.8%	7.11 ± 0.72	6.98 ± 0.71	0.08; 0.06 to 0.14	1.2; 0.8 to 2.0%
V @ 17.6%	6.01 ± 0.68	6.11 ± 0.67	0.09; 0.07 to 0.16	1.6; 1.2 to 2.8%
LV Slope	−0.19 ± 0.02	−0.21 ± 0.02	0.01; 0.01 to 0.01	4.4; 3.2 to 7.7%
L0	93.3 ± 8.2	90.99 ± 7.5	0.74; 0.53 to 1.26	1.8; 1.3 to 3.1%

TE = typical error; V = velocity (m·s⁻¹); LV slope = slope of the load–velocity relationship; L0 = theoretical load (gradient; %) at zero velocity.

Table 4. Relationship between LV variables measured during hill sprinting and mechanical properties of sprinting on flat terrain. Data are presented as mean; 90% confidence intervals

FVP Variable	L0		LV Slope
Maximal velocity (m·s^−1)	0.58; 0.3 to 0.77	***	−0.73; −0.86 to −0.52	***
V0 (m·s^−1)	0.54; 0.24 to 0.75	**	−0.76; −0.88 to −0.57	***
FVslope	−0.34; −0.61 to 0.01	*	−0.64; −0.81 to −0.38	***
F0 (N·kg^−1)	0.76; 0.57 to 0.88	***	0.02; −0.33 to 0.36
Pmax (W·kg^−1)	0.77; 0.59 to 0.88	***	−0.4; −0.65 to −0.06	*
RFmax	0.79; 0.61 to 0.89	***	−0.31; −0.59 to 0.03	*
DRF	−0.27; −0.56 to 0.09	*	−0.69; −0.84 to −0.46	***

V0 = maximal theoretical velocity; FVslope = slope of the force-velocity relationship; F0 = maximal theoretical force; P_max = maximal theoretical relative power; RF_max = maximal ratio of force horizontal:vertical force; DRF = decrease in ratio of force; * = likely; ** = very likely; *** = almost certainly.

Samozino, P., Rabita, G., Dorel, S., Slawinski, J., Peyrot, N., Saez de villarreal, E., & Morin, J. B. (2016). A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scandinavian Journal of Medicine & Science in Sports, 26(6), 648–658. https://doi.org/10.1111/sms.12490

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