Achilles tendon dimensions, ankle stiffness and footfall patterns in recreational runners

Figures & data

Table 1. Basic characteristics of the participants and variables investigated in rearfoot and non-rearfoot runners.

	Mean ± SD		Mean ± SD
Rearfoot runners [n = 87]
Age (years)	36.92 ± 8.07	AT length (%)	52.68 ± 4.06
Mass (kg)*	72.83 ± 13.02	AT thickness (mm)	5.24 ± 0.56
Height (m)	1.72 ± 0.08	AT moment arm (%)	19.69 ± 1.33
BMI (kg/m^2)*	24.38 ± 3.19	Speed (m/s)	2.78 ± 0.36
Fat (%)	23.20 ± 7.34	Foot strike index (%)*	10.58 ± 4.93
VISA-A (%)	92.21 ± 7.52	Foot angle IC_X (°)*	86.18 ± 4.43
Male/Female	40/47	Hip angle IC_X (°)	32.88 ± 6.84
Running distance per week (%) (km) (0–10/11–20/21–30/31–40/41–50/51<)	25/39/28/5/1/2	Knee angle IC_X (°)*	−7.41 ± 4.59
		Ankle angle IC_X (°)*	78.21 ± 3.70
		Ankle stiffness (Nm/°)*	17.21 ± 6.84
Non-rearfoot runners [n = 20]
Age (years)	33.42 ± 9.81	AT length (%)	50.89 ± 3.97
Mass (kg)*	64.18 ± 9.26	AT thickness (mm)	5.25 ± 0.49
Height (m)	1.71 ± 0.09	AT moment arm (%)	19.81 ± 1.27
BMI (kg/m^2)*	22.04 ± 2.62	Speed (m/s)	2.89 ± 0.45
Fat (%)	19.96 ± 7.30	Foot strike index (%)*	63.15 ± 10.81
VISA-A (%)	92.30 ± 7.94	Foot angle IC_X (°)*	62.68 ± 5.37
Male/Female	6/14	Hip angle IC_X (°)	33.05 ± 6.22
Running distance per week (%) (km) (0–10/11–20/21–30/31–40/41–50/51<)	30/30/25/10/0/5	Knee angle IC_X (°)*	−11.13 ± 3.86
		Ankle angle IC_X (°)*	56.23 ± 5.16
		Ankle stiffness (Nm/°)*	6.44 ± 2.24

Note: AT – Achilles tendon; IC – initial contact; BMI – body mass index; X – sagittal plane; VISA-A – Victorian Institute of Sport Assessment-Achilles questionnaire (Score 100% is maximum score associated with healthy AT); *statistically significant difference between rearfoot and non-rearfoot runners (p-value < 0.05).

Figure 1. Relationship between ankle joint stiffness and variables describing footfall pattern in rearfoot and non-rearfoot runners (a-c). Figure d shows the relationship between ankle joint stiffness and Achilles tendon thickness. p (BH) – p-value after applying Benjamini-Hochberg correction.

Table 2. The relationship between Achilles tendon dimensions and footfall pattern expressed by a partial correlation coefficient.

		FSI [%]		Foot angle IC [°]		Ankle angle IC [°]		Knee angle IC [°]		Hip angle IC [°]
		RF	NRF	RF	NRF	RF	NRF	RF	NRF	RF	NRF
Relative AT length [%]	r	−0.027	0.369	0.015	−0.157	0.086	−0.139	−0.081	−0.197	−0.125	0.017
	p	0.803	0.132	0.890	0.534	0.434	0.583	0.460	0.434	0.254	0.947
	p (BH)	0.901	0.607	0.930	0.768	0.768	0.766	0.756	0.739	0.649	0.905
AT thickness [mm]	r	0.148	−0.486	−0.119	0.412	−0.131	0.399	0.131	0.096	−0.186	−0.032
	p	0.177	0.041*	0.276	0.090	0.232	0.101	0.232	0.705	0.089	0.900
	p (BH)	0.582	0.377	0.668	0.518	0.667	0.516	0.628	0.853	0.585	0.920
Relative AT moment arm [%]	r	−0.054	−0.241	0.063	−0.077	−0.079	−0.261	0.135	0.234	−0.108	−0.056
	p	0.623	0.336	0.565	0.763	0.474	0.295	0.217	0.349	0.324	0.826
	p (BH)	0.796	0.672	0.788	0.877	0.752	0.646	0.665	0.669	0.677	0.947

Note: AT – Achilles tendon; FSI – foot strike index; IC – initial contact; RF – rearfoot runners; NRF – non-rearfoot runners; p (BH) – the p-value after applying Benjamini-Hochberg correction; *significant partial correlation (p-value < 0.05).

Figure 2. Relationship between Achilles tendonthickness and variables describing footfall pattern in rearfoot and non-rearfoot runners.