A Comparison of Ground Reaction Forces Determined by Portable Force-Plate and Pressure-Insole Systems in Alpine Skiing

Table 1 Unilateral values (Mean ± SD) for the variables of vGRFmax, vGRFmean (outside phase); vGRFmin, vGRFmean (inside phase); vGRFmin, vGRFmean (edge changing phase) determined by pressure insoles (PI) and force plates (FP) depending on the test situations: expert (n=10) vs. intermediate (n=10) level skiers, low vs. high dynamic skiing modes, on 15° (flat) vs. 23° (steep) slopes. When global significances for the factor “system” were observed, paired-sample t-tests between the force determined by the FP and the PI were additionally carried out. Significant differences between the systems are indicated by

			Expert group				Intermediate group				Interaction		Interaction		Interaction
			High dynamic skiing mode		Low dynamic skiing mode		High dynamic skiing mode		Low dynamic skiing mode		System x level		System x mode		System x slope
Variable	Unit	System	Flat slope	Steep slope	Flat slope	Steep slope	Flat slope	Steep slope	Flat slope	Steep slope	p	η_p²	p	η_p²	p	η_p²
vGRF_mean	[N/BW]	PI	.87 (.14)	.82 (.17)	.83 (.16)	.78 (.18)	.90 (.16)	.78 (.14)	.86 (.16)	.79 (.18)	.02	.29	.00	.39	.00	.79
vGRF_mean	[N/BW]	FP	1.26 (.08)*	1.15 (.08)*	1.27 (.08)*	1.18 (.10)*	1.18 (.13)*	1.01 (.11)*	1.15 (.11)*	1.04 (.10)*	.02	.29	.00	.39	.00	.79
vGRF_max	[N/BW]	PI	1.16 (.18)	1.22 (.21)	1.03 (.12)	1.06 (.18)	1.19 (.22)	1.11 (.21)	1.12 (.20)	1.09 (.25)	.00	.59	.39	.04	.06	.19
vGRF_max	[N/BW]	FP	1.91 (.18)*	2.05 (.20)*	1.76 (.09)*	1.86 (.13)*	1.68 (.25)*	1.61 (.21)*	1.59 (.14)*	1.60 (.20)*	.00	.59	.39	.04	.06	.19
vGRF_mean	[N/BW]	PI	.42 (.13)	.42 (.15)	.32 (.12)	.32 (.14)	.39 (.07)	.36 (.08)	.34 (.08)	.31 (.09)	.65	.01	.00	.42	.10	.15
vGRF_mean	[N/BW]	FP	.56 (.09)*	.62 (.13)*	.48 (.09)*	.49 (.13)*	.51 (.05)*	.53 (.06)*	.45 (.03)	.45 (.05)*	.65	.01	.00	.42	.10	.15
vGRF_min	[N/BW]	PI	.30 (.11)	.26 (.13)	.21 (.09)	.21 (.10)	.27 (.06)	.23 (.05)	.21 (.06)	.16 (.07)	.39	.04	.29	.07	.00	.44
vGRF_min	[N/BW]	FP	.27 (.04)	.15 (.09)	.26 (.06)	.26 (.10)	.26 (.08)	.20 (.10)	.27 (.06)	.19 (.11)	.39	.04	.29	.07	.00	.44
vGRF_mean	[N/BW]	PI	.60 (.13)	.49 (.14)	.58 (.19)	.49 (.19)	.54 (.12)	.41 (.12)	.49 (.11)	.42 (.11)	.04	.22	.00	.58	.01	.38
vGRF_mean	[N/BW]	FP	.76 (.09)*	.60 (.12)*	.83 (.22)*	.67 (.18*	.62 (.14)	.49 (.11)	.62 (.12)	.53 (.129	.04	.22	.00	.58	.01	.38
vGRF_min	[N/BW]	PI	.36 (.13)	.30 (.14)*	.31 (.16)	.26 (.12)	.33 (.10)	.23 (.08)*	.31 (.10)	.23 (.11)	.19	.10	.00	.58	.00	.60
vGRF_min	[N/BW]	FP	.34 (.10)	.15 (.09)	.37 (.10)	.26 (.11)	.27 (.10)	.09 (.08)	.31 (.11)	.15 (.14)	.19	.10	.00	.58	.00	.60

* Interaction effects (2 skier’s groups ×(2 systems ∙2 skiing modes ∙2 pitches)) repeated ANOVA) are indicated by the level of significance (p) and effect size (ηp). Data are means (±SD).