Correlation analysis of national elite Chinese male table tennis players’ shoulder proprioception and muscle strength

Table 1 Basic Information of the table tennis players (mean ± SD)

Subjects	Age (yr)	Height (cm)	Body weight (kg)	Training experience (yr)	Level of athlete
n = 19	17.87 ± 1.49	176.31 ± 4.19	66.67 ± 3.92	> 10	National Elite athlete

Table 2 Calculation and significance of proprioceptive evaluation indicators of the shoulder joint

Test	Evaluation index and its calculation methods	Meaning of the indicator
Joint position reproduction test of the shoulder joint	AE = (|Original error 1| + |Original error 2| + … + |Original error n|)/n	No positive or negative direction is considered. Only calculate the absolute error between the end position and the start position.
	CE = [(Original error 1) + (Original error 2) + … + (Original error n)]/n	Taking the positives and negatives in direction into account to evaluate overall the error in the given direction of movement, reflecting whether the movement pattern overall exceeds or fails to reach the target.
	VE =√{[(Original error 1-CE)2 + (Original error 2-CE)2 + … + (Original error n-CE)2]/n}	Reflects the variability and consistency between the results of several position reproduction, regardless of the accuracy of the JPR.

AE: Absolute error; CE: Constant error; VE: Variable error; JPR: Joint Position Reproduction test.

Table 3 Correlation analysis of strength and proprioception at 60°/s in the shoulder joint of the racket-holding hand in table tennis players

		Absolute peak torque of external rotation	Relative peak torque of external rotation	Absolute peak torque of internal rotation	Relative peak torque of internal rotation
External rotation AE	Spearman	-0.055	-0.148	-0.059	-0.178
	P value	0.818	0.533	0.806	0.454
External rotation CE	Spearman	-0.234	-0.315	-0.197	-0.344
	P value	0.321	0.176	0.405	0.137
External rotation VE	Pearson	0.302	0.136	0.330	0.162
	P value	0.196	0.568	0.155	0.495
Internal rotation AE	Pearson	0.223	0.018	0.199	0.001
	P value	0.344	0.939	0.399	0.997
Internal rotation CE	Pearson	0.175	-0.139	0.220	-0.097
	P value	0.459	0.558	0.351	0.683
Internal rotation VE	Spearman	-0.024	0.086	-0.097	0.043
	P value	0.920	0.719	0.685	0.857

AE: Absolute error; CE: Constant error; VE: Variable error.

Table 4 Correlation analysis of strength and proprioception at 180°/s in the shoulder joint of the racket-holding hand in table tennis players

		Absolute Peak torque of external rotation	Relative peak torque of external rotation	Absolute peak torque of internal rotation	Relative peak torque of internal rotation
External rotation AE	Spearman	-0.111	-0.150	-0.204	-0.214
	P value	0.640	0.529	0.388	0.366
External rotation CE	Spearman	-0.113	-0.347	-0.123	-0.420
	P value	0.636	0.133	0.604	0.065
External rotation VE	Pearson	0.033	0.057	0.040	0.091
	P value	0.890	0.812	0.868	0.704
Internal rotation AE	Pearson	0.114	0.082	0.066	0.076
	P value	0.633	0.732	0.782	0.749
Internal rotation CE	Pearson	0.168	-0.145	0.245	-0.105
	P value	0.478	0.542	0.297	0.660
Internal rotation VE	Spearman	0.053	0.221	-0.081	0.117
	P value	0.826	0.349	0.736	0.623

AE: Absolute error; CE: Constant error; VE: Variable error.

Table 5 Correlation analysis of strength and proprioception at 60°/s in the shoulder of non-racket-holding hands of table tennis players

		Absolute peak torque of external rotation	Relative peak torque of external rotation	Absolute peak torque of internal rotation	Relative peak torque of internal rotation
External rotation AE	Pearson	-0.044	0.063	-0.077	0.041
	P value	0.855	0.793	0.747	0.863
External rotation CE	Spearman	-0.071	0.068	-0.027	0.072
	P value	0.765	0.774	0.909	0.762
External rotation VE	Spearman	-0.203	-0.156	-0.138	-0.103
	P value	0.391	0.510	0.561	0.666
Internal rotation AE	Pearson	-0.042	0.093	-0.095	0.050
	P value	0.860	0.695	0.690	0.835
Internal rotation CE	Pearson	0.084	-0.015	0.118	0.020
	P value	0.725	0.950	0.620	0.932
Internal rotation VE	Spearman	0.375	0.477a	0.289	0.384
	P value	0.103	0.033a	0.217	0.094

^aP < 0.05, muscle strength vs proprioception.

AE: Absolute error; CE: Constant error; VE: Variable error.

Table 6 Correlation analysis of the strength and proprioception at 180°/s in the shoulder joint in the non-racket-holding hand of table tennis players

		Absolute peak torque of external rotation	Relative peak torque of external rotation	Absolute peak torque of internal rotation	Relative peak torque of internal rotation
External rotation AE	Pearson	-0.266	0.046	-0.351	-0.025
	P value	0.257	0.847	0.129	0.917
External rotation CE	Spearman	-0.236	-0.099	-0.065	-0.093
	P value	0.318	0.679	0.786	0.697
External rotation VE	Spearman	0.040	0.083	-0.026	0.136
	P value	0.867	0.729	0.914	0.569
Internal rotation AE	Pearson	0.003	-0.070	-0.087	-0.120
	P value	0.990	0.771	0.715	0.615
Internal rotation CE	Pearson	-0.142	0.163	-0.076	0.184
	P value	0.551	0.492	0.751	0.437
Internal rotation VE	Spearman	0.202	0.554a	-0.226	0.389
	P value	0.394	0.011a	0.339	0.090

^aP < 0.05 forces vs proprioception.

AE: Absolute error; CE: Constant error; VE: Variable error.

Table 7 Comparison of the Internal and external rotation’s absolute error, constant error and variable error of the racket-holding and the non-racket-holding hand

	External rotation AE	External rotation CE	External rotation VE	Internal rotation AE	Internal rotation CE	Internal rotation VE
Z value	-0.947	-1.244	-0.987	-0.906	-3.991	-3.138
P value	0.355	0.221	0.327	0.369	< 0.01a	< 0.01a

^aP < 0.01, the internal rotation constant error, variable error of the racket-holding hand vs that of the non-racket-holding hand.

AE: Absolute error; CE: Constant error; VE: Variable error.