Monitoring of postural sway with a head-mounted wearable device: effects of gender, participant state, and concussion

Figures & data

Figure 1 Combined head-impact and postural sway monitoring inertial motion unit sensors (A) worn with an athletic headband; and (B) attached to the skin using an adhesive patch.

Figure 2 Cumulative distributions for different measures of postural stability, plotted as a function of eye state and gender. Measures of sway power (in Watts) were significantly different for eyes open (Eo) versus eyes closed (Ec) and as a function of gender. After normalization, the ratio of sway power with Ec/Eo did not differ as a function of gender. The Front-back sway power ratio was significantly different: with eyes closed participants moved more posteriorly. There were no differences in the left-right sway power ratio as a function of gender or eye state.

Table 1 Measurements of sway power and sway power asymmetry (front/back ratio and left/right ratio) as a function of participant gender

Eyes	Gender	Power			Front/back ratio			Left/right ratio
		Mean	95% CI	p	Mean	95% CI	p	Mean	95% CI	p
Open	Men	0.519	0.468–0.569	*, ∆	0.023	−0.016–−0.062	x	0.005	−0.045–0.055	ns
	Women	0.487	0.419–0.556		0.014	−0.022–0.050		0.029	−0.020–0.078
Closed	Men	0.628	0.573–0.683		−0.028	−0.051–−0.005		0.007	−0.025–0.039
	Women	0.551	0.483–0.619		−0.013	−0.039–0.014		0.010	−0.020–0.041
Closed/open	Men	1.313	1.244–1.383	ns			ns			ns
	Women	1.286	1.214		1.358

Notes: *p<0.0001 main effect of eyes. ∆ p<0.001 main effect of gender. x p<0.002 main effect of eyes. Separate measures were obtained with the eyes open and eyes closed. 

Abbreviation: ns, not significant.

Figure 3 The influence of nicotine use (within 1–8 hrs) on postural sway.

Table 2 Influence of participant state variables on measures of sway power and sway power asymmetry (front/back ratio and left/right ratio)

Condition	Gender	n	Power									Forward/backward						Left/right
			Open			Closed			Closed/open			Open			Closed			Open			Closed
			Mean	95% CI	p	Mean	95% CI	p	Mean	95% CI	p	Mean	95% CI	p	Mean	95% CI	p	Mean	95% CI	p	Mean	95% CI	P
Caffeine use
No	Female	31	0.449	0.253-0.644		0.424	0.328-0.519		1.243	1.061-1.426		−0.028	−0.072-0.017		−0.012	−0.067-0.043		0.081	0.028-0.134		0.059	0.006-0.112
Yes	Female	165	0.495	0.424-0.566	ns	0.575	0.498-0.651	ns	1.294	1.218-1.371	ns	0.022	−0.019-0.062	ns	−0.013	−0.042-0.017	ns	0.019	−0.038-0.076	ns	0.001	−0.033-0.035	ns
No	Male	27	0.553	0.434-0.671		0.663	0.553-0.773		1.294	1.133-1.455		−0.003	−0.07-0.064		−0.057	−0.133-0.019		−0.004	−0.076-0.068		0.032	−0.069-0.133
Yes	Male	123	0.511	0.456-0.566		0.62	0.559-0.681		1.318	1.241-1.394		0.029	−0.016-0.074		−0.022	−0.043-0		0.007	−0.05-0.065		0.002	−0.03-0.033
Nicotine use
No	Female	172	0.466	0.402–0.531		0.538	0.465–0.610		1.287	1.215-1.359		0.007	−0.026-0.041		−0.018	−0.046-0.01		0.012	−0.039-0.063		0.006	−0.025-0.037
Yes	Female	24	0.639	0.335–0.943	%	0.645	0.457–0.833	*	1.279	1.013-1.546	ns	0.063	−0.094-0.221	ns	0.025	−0.042-0.092	ns	0.149	0.008-0.29	ns	0.04	−0.064-0.145	ns
No	Male	103	0.499	0.434–0.564		0.582	0.522–0.641		1.303	1.215-1.391		0.007	−0.041-0.054		−0.037	−0.066-−0.008		0.009	−0.045-0.064		−0.013	−0.054-0.029
Yes	Male	47	0.561	0.488–0.634		0.729	0.623–0.836		1.335	1.223-1.448		0.06	−0.007-0.126		−0.009	−0.04-0.023		−0.004	−0.105-0.097		0.05	0.013-0.088
Hours since last meal
1	Female	64	0.457	0.373-0.54		0.572	0.445-0.698		1.326	1.204-1.448		0.026	−0.034-0.085		−0.025	−0.064-0.014		−0.074	−0.19-0.043		0.028	−0.016-0.071
4	Female	97	0.473	0.382-0.563	ns	0.541	0.447-0.636	ns	1.302	1.201-1.404	ns	0.004	−0.049-0.056	ns	−0.007	−0.045-0.031	ns	0.095	0.048-0.143	ns	0.007	−0.037-0.05	ns
8	Female	35	0.585	0.35-0.821		0.538	0.4-0.676		1.169	1.006-1.333		0.022	−0.055-0.099		−0.006	−0.079-0.068		0.032	−0.062-0.125		−0.012	−0.096-0.071
1	Male	50	0.567	0.469-0.664		0.656	0.57-0.743		1.29	1.17-1.41		−0.005	−0.065-0.056		−0.031	−0.079-0.017		−0.02	−0.103-0.063		−0.03	−0.094-0.034
4	Male	75	0.502	0.436-0.569		0.609	0.529-0.69		1.293	1.199-1.388		0.037	−0.024-0.098		−0.025	−0.052-0.002		0.039	−0.036-0.114		0.037	−0.002-0.076
8	Male	25	0.471	0.369-0.574		0.628	0.498-0.758		1.42	1.235-1.604		0.038	−0.038-0.114		−0.03	−0.077-0.017		−0.045	−0.133-0.043		−0.01	−0.08-0.06
Amount eaten relative to usual
Less	Female	44	0.545	0.4195-0.5554		0.561	0.4827-0.6187		1.309	1.2139-1.3584		0.035	−0.022-0.0499		0.003	−0.039-0.0135		0.094	−0.02-0.0777		−0.013	−0.02-0.0407
Less	Male	40	0.573	0.4686-0.5687	ns	0.651	0.573-0.6831	ns	1.271	1.2434-1.3832	ns	0.05	−0.016-0.0623	ns	−0.041	−0.051-−0.005	ns	0.017	−0.045-0.0557	ns	−0.023	−0.025-0.0388	ns
More	Female	15	0.637	0.4189-0.5559		0.858	0.4818-0.6195		1.27	1.2144-1.3579		0.06	−0.021-0.0494		−0.104	−0.039-0.0138		0.035	−0.021-0.0781		−0.017	−0.02-0.0405
Moe	Male	16	0.375	0.468-0.5693		0.568	0.5731-0.6831		1.537	1.2428-1.3839		−0.07	−0.016-0.0619		−0.044	−0.051-−0.005		0.062	−0.044-0.0548		0.057	−0.025-0.039
Usual	Female	137	0.452	0.4203-0.5546		0.514	0.4832-0.6182		1.281	1.2138-1.3584		0.003	−0.021-0.0495		−0.008	−0.039-0.014		0.007	−0.02-0.0777		0.021	−0.02-0.0401
Usual	Male	94	0.52	0.4682-0.5691		0.628	0.5731-0.6831		1.293	1.243-1.3836		0.028	−0.016-0.0625		−0.02	−0.051-−0.005		−0.01	−0.045-0.055		0.011	−0.025-0.0386
Exercise day of study
No	Female	168	0.501	0.425-0.577		0.553	0.479-0.628		1.266	1.19-1.343		0.021	−0.019-0.061		−0.009	−0.038-0.021		0.02	−0.036-0.076		0.001	−0.032-0.034
Yes	Female	28	0.408	0.296-0.52	ns	0.536	0.396-0.675	ns	1.405	1.23-1.58	ns	−0.029	−0.08-0.023	ns	−0.035	−0.076-0.006	ns	0.081	0.017-0.146	ns	0.068	0.007-0.128	ns
No	Male	118	0.491	0.445-0.537		0.629	0.572-0.687		1.356	1.281-1.431		0.03	−0.012-0.073		−0.028	−0.054-−0.002		−0.013	−0.068-0.042		−0.005	−0.04-0.03
Yes	Male	32	0.621	0.464-0.778		0.623	0.483-0.763		1.156	0.995-1.317		−0.004	−0.095-0.088		−0.028	−0.071-0.014		0.072	−0.035-0.179		0.052	−0.015-0.118
Exercise Intensity
Light	Female	11	0.423	0.264-0.582		0.574	0.357-0.79		1.455	1.142-1.768		−0.029	−0.115-0.056		−0.026	−0.083-0.031		0.139	0.068-0.21		0.088	−0.008-0.183
Moderate	Female	15	0.406	0.228-0.583	ns	0.527	0.319-0.734	ns	1.408	1.179-1.637	ns	−0.025	−0.1-0.051	ns	−0.049	−0.114-0.016	ns	0.024	−0.073-0.121	ns	0.067	−0.021-0.156	ns
Strenuous	Female	2	0.339	0.207-0.471		0.393	0.07-0.716		1.106	0.583-1.629		−0.053	−0.127-0.022		0.017	−0.074-0.108		0.191	−0.104-0.486		−0.04	−0.086-0.005
Light	Male	6	0.45	0.259-0.64		0.625	0.278-0.972		1.456	1.076-1.836		−0.158	−0.248-−0.067		−0.071	−0.141-0		0.042	−0.014-0.098		0.036	−0.037-0.109
Moderate	Male	16	0.724	0.481-0.966		0.691	0.469-0.913		1.127	0.894-1.361		0.028	−0.141-0.197		−0.039	−0.088-0.011		0.149	−0.037-0.335		0.044	−0.028-0.116
Strenuous	Male	10	0.559	0.266-0.851		0.514	0.325-0.703		1.022	0.775-1.269		0.039	−0.039-0.116		0.014	−0.088-0.115		−0.032	−0.188-0.123		0.074	−0.107-0.255
Amount of Sleep
Less	Female	52	0.554	0.375-0.734		0.564	0.45-0.678		1.233	1.099-1.367		−0.02	−0.068-0.028		−0.009	−0.048-0.03		0.012	−0.059-0.082		0.037	−0.015-0.088
More	Female	50	0.493	0.377-0.61	ns	0.545	0.395-0.694	ns	1.266	1.13-1.401	ns	0.055	−0.021-0.132	ns	−0.04	−0.087-0.008	ns	0.044	−0.036-0.124	ns	0.033	−0.008-0.074	ns
Usual	Female	94	0.447	0.37-0.524		0.547	0.45-0.643		1.326	1.221-1.431		0.011	−0.043-0.065		0	−0.043-0.043		0.03	−0.054-0.114		−0.017	−0.067-0.034
Less	Male	23	0.568	0.39-0.747		0.579	0.456-0.703		1.223	1.023-1.422		0.102	−0.063-0.268		−0.02	−0.068-0.028		0.059	−0.147-0.265		0.025	−0.032-0.081
More	Male	28	0.496	0.403-0.588		0.687	0.522-0.852		1.391	1.204-1.578		−0.021	−0.06-0.019		−0.079	−0.149-−0.008		−0.02	−0.102-0.062		−0.045	−0.143-0.053
Usual	Male	99	0.514	0.456-0.571		0.623	0.562-0.684		1.312	1.235-1.39		0.017	−0.025-0.06		−0.016	−0.04-0.009		0	−0.052-0.052		0.018	−0.018-0.054
Medications
No	Female	131	0.462	0.392-0.532		0.506	0.440–0.572		1.269	1.181-1.357		0.013	−0.033-0.059		−0.029	−0.06-0.001		0.005	−0.063-0.073		0.007	−0.028-0.043
Yes	Female	65	0.539	0.394-0.684	ns	0.641	0.492–0.791	*	1.321	1.202-1.439	ns	0.016	−0.033-0.065	ns	0.021	−0.028-0.069	ns	0.077	0.026-0.128	ns	0.016	−0.039-0.071	ns
No	Male	118	0.501	0.447-0.556		0.618	0.556–0.679		1.324	1.248-1.4		0.008	−0.03-0.046		−0.026	−0.053-0.001		−0.001	−0.042-0.04		0.01	−0.029-0.048
Yes	Male	32	0.582	0.468-0.697		0.666	0.555–0.777		1.275	1.113-1.436		0.08	−0.033-0.192		−0.036	−0.069-−0.004		0.028	−0.147-0.203		−0.002	−0.046-0.041
Alcohol within 8 hrs
No	Female	173	0.47	0.409-0.53		0.539	0.47-0.608		1.291	1.214-1.367		0.02	−0.019-0.058		−0.012	−0.04-0.016		0.012	−0.041-0.066		0.006	−0.025-0.037
Yes	Female	23	0.622	0.279-0.966	ns	0.64	0.401-0.879	ns	1.251	1.076-1.427	ns	−0.027	−0.101-0.046	ns	−0.017	−0.096-0.062	ns	0.152	0.067-0.237	ns	0.041	−0.054-0.136	ns
No	Male	118	0.521	0.466-0.575		0.638	0.575-0.701		1.324	1.241-1.407		0.025	−0.02-0.069		−0.029	−0.055-−0.003		0.003	−0.054-0.059		0.01	−0.028-0.048
Yes	Male	32	0.511	0.392-0.629		0.592	0.493-0.692		1.274	1.165-1.383		0.018	−0.06-0.095		−0.024	−0.066-0.019		0.014	−0.085-0.113		−0.004	−0.053-0.045
Recreational drugs within 8 hrs
No	Female	171	0.478	0.416-0.54		0.555	0.482-0.628		1.285	1.211-1.36		0.02	−0.018-0.058		−0.014	−0.043-0.015		0.016	−0.038-0.07		0.011	−0.022-0.043
Yes	Female	25	0.553	0.236-0.869	ns	0.524	0.363-0.686	ns	1.291	1.076-1.506	ns	−0.025	−0.109-0.058	ns	−0.002	−0.044-0.041	ns	0.115	0.02-0.21	ns	0.007	−0.057-0.071	ns
No	Male	132	0.512	0.46-0.564		0.622	0.565-0.679		1.319	1.245-1.392		0.019	−0.024-0.061		−0.024	−0.048-0		0.018	−0.035-0.07		0.008	−0.026-0.043
Yes	Male	18	0.569	0.41-0.727		0.671	0.509-0.833		1.275	1.066-1.484		0.056	−0.024-0.136		−0.057	−0.116-0.002		−0.086	−0.212-0.04		−0.001	−0.069-0.066

Notes: ^%p<0.06 significant main effect of condition. *p<0.05 significant main effect of condition. Data are further subdivided by gender based on the significant differences shown in Table 1.

Abbreviation: ns, not significant.

Figure 4 Repeated measures of sway in 22 men’s professional soccer players recorded over 15 sessions spanning 37 days. (A) Sway power; (B) Bias in lateral sway; (C) Eyes closed/eyes open sway power ratio.

Abbreviation: L-R, left-right.

Figure 5 Variability of sway measurements from 22 men’s professional soccer players recorded over 15 sessions spanning 37 days. (A) Sway power; (B) Bias in lateral sway; (C) Eyes closed/eyes open sway power ratio.

Abbreviation: L-R, left-right.

Figure 6 The effect of physical activity on sway in two sports. The measures were obtained in college women’s soccer and volleyball teams and reflect repeated measures before and after training sessions over 6 weeks during the fall 2018 season. Sway power increases significantly after physical activity.

Abbreviation: L-R, Left-right

Figure 7 The effect of an acute concussion on sway power in a varsity high school football player. Player 4 sustained an in-practice concussion, leading to a significant increase of postural sway post practice (A). Over the next two weeks, there is a clear pattern of recovery to baseline (B).

Abbreviations: Eo, eyes open; Ec, eyes closed.