. 2020 Sep 10;10:14903. doi: 10.1038/s41598-020-71763-8

Table 2.

Results of the linear regression models having as possible predictors (in blocks of rows): only Speed (first row), only AgeGroup (second row), Speed + AgeGroup (third row), and Speed + AgeGroup + Speed × AgeGroup (fourth row), for each of the features: peak power (P), total positive work (W+), and total negative work (W−) at the ankle, foot, and sum of the ankle and foot.

Feature	Predictor						Goodness of fit
	Speed		Age		Speed × Age		Goodness of fit
	β_S	CI	β_A	CI	β_SA	CI	LLF	AIC	R²
Pankle	0.87**	[0.80, 0.93]					− 66.8	141.6	0.78
			− 0.19	[− 0.57, 0.19]			− 171.4	350.9	0.01
	0.87**	[0.80, 0.93]	− 0.11	[− 0.37, 0.14]			− 67.5	145.1	0.78
	0.91**	[0.83, 0.99]	− 0.12	[− 0.37, 0.14]	− 0.12	[− 0.25, 0.00]	− 67.6	147.2	0.78
Pfoot	0.79**	[0.70, 0.88]					− 102.8	213.5	0.63
			− 0.03	[− 0.43, 0.36]			− 171.6	351.2	0.00
	0.79**	[0.70, 0.88]	0.04	[− 0.28, 0.35]			− 103.7	217.3	0.63
	0.85**	[0.73, 0.96]	0.03	[− 0.27, 0.34]	− 0.15	[− 0.33, 0.03]	− 103.8	219.6	0.64
Psum	0.83**	[0.77, 0.90]					− 73.9	155.8	0.72
			− 0.26	[− 0.65, 0.14]			− 170.7	349.4	0.02
	0.83**	[0.77, 0.90]	− 0.18	[− 0.47, 0.11]			− 74.1	158.3	0.73
	0.88**	[0.80, 0.96]	− 0.18	[− 0.47, 0.10]	− 0.11	[− 0.24, 0.02]	− 74.5	161.1	0.73
W+ ankle	0.74**	[0.66, 0.82]					− 100.5	209.0	0.56
			− 0.25	[− 0.68, 0.19]			− 168.7	345.5	0.01
	0.73**	[0.65, 0.81]	− 0.18	[− 0.55, 0.19]			− 100.8	211.6	0.57
	0.79**	[0.69, 0.89]	− 0.18	[− 0.55, 0.18]	− 0.14	[− 0.30, 0.03]	− 101.0	213.9	0.57
W+ foot	0.52**	[0.40, 0.64]					− 141.7	291.3	0.27
			− 0.21	[− 0.68, 0.26]			− 166.3	340.6	0.01
	0.52**	[0.40, 0.64]	− 0.16	[− 0.61, 0.28]			− 142.0	294.0	0.28
	0.47**	[0.32, 0.62]	− 0.16	[− 0.61, 0.29]	0.13	[− 0.12, 0.38]	− 142.6	297.2	0.27
W+ sum	0.66**	[0.58, 0.75]					− 109.1	226.2	0.49
			− 0.36	[− 0.82, 0.10]			− 165.2	338.4	0.03
	0.66**	[0.58, 0.75]	− 0.30	[− 0.69, 0.09]			− 108.7	227.4	0.51
	0.70**	[0.60, 0.81]	− 0.30	[− 0.69, 0.09]	− 0.11	[− 0.29, 0.06]	− 109.4	230.7	0.51
W-ankle	0.29**	[0.18, 0.39]					− 140.8	289.6	0.05
			0.39	[− 0.14, 0.93]			− 149.6	307.1	0.04
	0.29**	[0.18, 0.40]	0.42	[− 0.13, 0.97]			− 140.0	290.1	0.09
	0.26*	[0.12, 0.40]	0.42	[− 0.13, 0.97]	0.08	[− 0.15, 0.30]	− 141.1	294.1	0.09
W-foot	− 0.82**	[− 0.90, − 0.73]					− 98.2	204.3	0.65
			− 0.36	[− 0.73, 0.00]			− 170.1	348.2	0.03
	− 0.82**	[− 0.90, − 0.74]	− 0.44*	[− 0.71, − 0.16]			− 94.8	199.6	0.70
	− 0.72**	[− 0.82, − 0.62]	− 0.44*	[− 0.71, − 0.17]	− 0.26*	[− 0.43, − 0.10]	− 91.7	195.4	0.72
W-sum	− 0.26**	[− 0.37, − 0.15]					− 142.3	292.5	0.10
			0.04	[− 0.51, 0.60]			− 149.9	307.9	0.00
	− 0.26**	[− 0.37, − 0.14]	0.02	[− 0.52, 0.56]			− 142.7	295.3	0.10
	− 0.23*	[− 0.38, − 0.09]	0.02	[− 0.52, 0.55]	− 0.07	[− 0.31, 0.17]	− 143.7	299.4	0.10

The following statistics are presented: regression coefficients (slopes) for the terms Speed (β_S), AgeGroup (β_A) and Speed × AgeGroup (β_SA), 95% confidence interval for the slopes (CI), log-likelihood (LLF), Akaike Information Criterion (AIC), and coefficient of determination between predicted and actual feature values (R²). Statistically significant (α = 0.05) slopes are in bold and the p value for the t test of the null-hypothesis significance test is indicated with * if p < 0.005 or ** if p < 0.0001. The coefficients for Speed (β_S) and values of the features are standardized; AgeGroup is a categorical factor (Young = 0, Older = 1).