Wen-Hsu Sung

The comparisons of heart rate variability and perceived exertion during simulated cycling with various viewing devices

Sympathovagal modulation during immersion in a virtual environment is an important influence on human performance of a task. The aim of this study is to investigate sympathovagal modulation using heart rate variability and perceived exertion during exercise in a virtual reality (VR) environment. Sixteen young healthy volunteers were tested while using a stationary bicycle and maintained at an anaerobic threshold intensity for exercise sessions of approximately 10 min duration. Four randomized viewing alternatives were provided including desktop monitor, projector, head mounted device (HMD), and no simulation display. The no simulation display served as the control group. A quick ramp exercise test was conducted and maintained at an anaerobic threshold intensity for each session to evaluate power spectral density and rating of perceived exertion (RPE). The sampled heart rate data were rearranged by cubic spline interpolation into power spectrums spanning the ultra-low frequency (ULF) to high frequency (HF) range. A significant difference was found between the no-display and projector groups for total power (TP) and very low frequency (VLF) components. In particular, there was a significant difference when comparing HMD and no-display exercise RPE curves within 6 min of cycling and at the termination of the exercise. A significant difference was also achieved in projector vs. control group comparison at the termination of the exercise. Our results indicate that the use of HMD and the projected VR during cycling can reduce the TP and VLF power spectral density through a proposed decrease in the renin-angiotensin system, with the implication that this humoral effect may enable anaerobic exercise for longer durations through a reduction in sympathetic tone and subsequent increased blood flow to the muscles.

Feasibility of a smartphone-based balance assessment system for subjects with chronic stroke

BACKGROUNDnStroke is a cerebral artery disease that may lead to long-term disabilities or death. Patients that survive a stroke usually suffer balance impairments, which affect their performance in activities of daily living (ADLs) and quality of life (QoL). In recent years, smartphones have become very popular and have many capabilities. Smartphone built-in sensors have shown their ability and potential in balance performance assessment. However, the feasibility of smartphones on subjects with chronic strokes remains to be proved. Therefore, the purpose of this study is to evaluate the feasibility of a smartphone-based balance assessment system for subjects with chronic stroke.nnnMETHODSnTen subjects with chronic stroke and thirteen healthy adults were recruited in the study. The smartphone HTC 10 (HTC Corporation, Taiwan) was used to perform the balance assessment, and its built-in accelerometer and gyroscope were used to record data from the subjects. Six postures were tested for thirty seconds each: shoulder-width stance (SWS) with eyes opened (E/O) and eyes closed (E/C), feet-together stance (FTS) with E/O and E/C, and semi-tandem stance (STS) with E/O and E/C. The smartphone was fixed to the back of subjects at the second sacral spine (S2) level. The changes registered in the accelerometer and gyroscope data were used to represent the balance performance, in which higher values indicate more instability. Data was analyzed using the independent t-test with the software SPSS 20, and the statistical significance level was set to αu202f<u202f0.05.nnnRESULTS AND DISCUSSIONnSignificant difference in the acceleration data was found among subjects with chronic stroke and healthy adults under four assessment postures: SWS with E/C (pu202f=u202f0.048), FTS with E/O (pu202f=u202f0.027), FTS with E/C (pu202f=u202f0.000), and STS with E/C (pu202f=u202f0.048). Furthermore, according to the gyroscope data, there were significant differences in how the two groups performed the postures. The results demonstrate that a smartphone with a built-in accelerometer and gyroscope can be used to classify balance performances between healthy adults and subjects with chronic stroke.nnnCONCLUSIONnThis study shows that smartphones are feasible to assess balance for subjects with chronic stroke.

Analysis of trunk rolling in Parkinson's disease patients using a mattress mobility detection system

BACKGROUND AND OBJECTIVEnParkinsons disease (PD) is a neurodegenerative condition characterized by motor dysfunction and various types of non-motor impairments. The reaction time and movement time are reported to become more severe delayed in worse PD patients. Most tools for evaluating motor impairment are limited by relying on subjective observations and being qualitative in design. The aim of this study was to investigate trunk rolling performance in PD patients by using a recently developed system to detect turning in bed.nnnMETHODSnThe study included 20 PD patients and 42 healthy controls. A mattress mobility detection system was employed for quantitative measurements. Each test session consisted of subjects starting by lying in a supine position on a bed and rolling 10 times onto their left side and 10 times onto their right side. Strain gauges mounted under the feet of the bed recorded changes in the center of pressure (CoP).nnnRESULTSnFor turning back, the patients compared with the controls had significantly longer movement time (Pu202f=u202f0.017), longer time to peak counteraction (Pu202f=u202f0.001), larger ratio of peak counteraction to movement time (Pu202f=u202f0.006), shorter CoP displacement (Pu202f<u202f0.0001), slower turning speed (Pu202f=u202f0.000), weaker peak counteraction (Pu202f=u202f0.013), and smaller ratio of peak counteraction to weight (Pu202f=u202f0.032). Results for turning over were similar except there was no significant difference in the ratio of peak counteraction to weight.nnnCONCLUSIONSnThe mattress mobility detection system was useful for objectively assessing trunk rolling performance of PD patients. Improved assessment of trunk function in PD patients could lead to better treatments and improved rehabilitation procedures.

Computer-aided vestibular autorotational testing of the vestibulo-ocular reflex in senile vestibular dysfunction

BACKGROUND AND OBJECTIVEnStudies have already investigated vestibulo-ocular reflex (VOR) responses in elderly subjects, mostly at low frequencies (<1 Hz) during passive head turns, or continuous active head turns in a rotational chair. However, natural head movements usually occur at frequencies above 1 Hz and at varying rates, rather than at continuously increasing rates as tested in most studies to date. The aim of this study was to compare VOR responses within or between normal and bilateral peripheral vestibular hypofunction (BPVH) elderly subjects with a computer base program incorporating random active high-frequency head movements.nnnSUBJECTSnSeventeen senior patients with bilateral peripheral vestibular hypofunction and 13 age-matched paid healthy subjects participated in this study.nnnDESIGNnAll the subjects performed 8s of active, side-to-side head motions at 1 Hz, 2 Hz and 3 Hz in response to four experimental conditions: (A) a stationary visual target; (B) a stationary visual target and a moving target with a horizontal trajectory; (C) a stationary visual target and a moving target with a spiral trajectory; and (D) a stationary visual target with combined horizontal- and vertical-spiral moving targets.nnnRESULTSnRepeated-measures ANOVA showed that across the different frequencies of headshaking, a significant increase took place in the phase lag of the BPVH subjects (p<0.001) compared with the normal controls. Post hoc analysis showed significant within-group differences in BPVH subjects (1 Hz vs 2 Hz, 2 Hz vs 3 Hz) and normal controls (1 Hz vs 2 Hz, 1 Hz vs 3 Hz). A significant VOR gain took place among the BPVH subjects at 3 Hz VAT (p<0.001) as compared with 1 Hz VAT and no significant differences in VOR gain could be detected among the controls at either of these frequencies. Repeated-measures ANOVA revealed that under our test conditions, significant main effect was noted for VOR asymmetry (F=4.45, p<0.05). Post hoc analysis showed significant within-group differences in the BPVH subjects (test A vs test B, test A vs test C, and test A vs test D).nnnCONCLUSIONSnOur results showed that the VAT paradigm can be improved by using concurrent horizontal and vertical moving targets. The VOR phase may be useful for differentiating VAT responses between BPVH and healthy elderly subjects. Moreover, the results of this study demonstrate that gains in VOR at different frequencies of headshaking and asymmetry during different test conditions can be useful parameters for within-group assessment.