Combining multiple human physiological signals using fuzzy logic to determine stress caused by battle dress uniforms

Abstract

This study presents a novel stress index for clothing using physiological signals to estimate stress induced by battle dress uniforms (BDU) during physical activity. The approach uses a fuzzy logic-based nonlinear mapping to compute the stress from physiological signals. Ten healthy men performed a battery of physical activities in a controlled environment. Heart rate (HR), respiration rate (RR), skin temperature (ST), and galvanic skin response (GSR) were measured continuously for the participants during activity wearing three kinds of clothing (two BDUs and a control garment). The individual physiological responses were combined using a fuzzy-logic system to derive a stress measure called Clothed Activity Stress Index (CASI). Repeated measures ANOVA showed that the garments significantly (α = .05) affected the HR (p < .001) and RR (p < .001). In addition, interactions between the activity and garment were significant for HR, RR, and ST (p < .001, p < .001, p < .036). The physiological measures differed significantly between rest and activity for the two uniforms. The stress indices (ranging between 0 and 1) during rest and activity were 0.24 and 0.35 for control, 0.27 and 0.43 for BDU-1, and 0.33 and 0.44 for BDU-2. It is shown here that clothing systems impact human stress levels to a measurable level. This computational approach is applicable to measure stress caused by protective wear under different operational conditions and can be suitable for sports and combat gears.

Article Highlights

Effects of personal protective clothing on firefighters' gait analyzed using 3D motion capture system

OBJECTIVES

The effects of personal protective clothing (PPC) on firefighters' gait were investigated to develop high-performance PPC.

METHODS

Thirteen participants participated in human trials with three types of PPC (firefighter protective clothing (FPC); semi-enclosed chemical protective clothing (CPC_semi); full-enclosed chemical protective clothing (CPC_full)) and T-shirt (CON). A 3D motion capture system was used to obtain gait parameters (step length, step width, stride frequency, gait speed, and toe-out angle) and the range of motion (ROM) of the joints (hip, knee, and ankle).

RESULTS

PPCs produced an increase in step width (23.4%, p > 0.05), but the gait speed (9.1%) and stride frequency (6.4%) decreased compared with the CON results. ROM is affected by the PPC type and joint. FPC and CPC_semi had no significant effect in terms of the ROM of the hip and knee besides the landing angle of the knee. However, CPC_full had a significant effect on the maximum extension angle of the hip and maximum flexion angle of the knee, which reached up to 27.2%.

CONCLUSION

The ROM of the firefighter's lower limbs were limited by PPC. This study offers insights into next-generation PPC design and development, as well as guidelines for training and firefighting.

Assessment of a Marksmanship Simulator as a Tool for Clothing and Individual Equipment Evaluation

Marksmanship performance has traditionally been used in the military to assess individual and unit operational readiness. In more recent years, marksmanship simulator trainers have been utilized to reduce cost and time for weapons handling training and skills retention. However, they have not been readily utilized for product and equipment evaluation purposes. This study assesses the sensitivity of the marksmanship simulator for use during clothing and individual equipment (CIE) product evaluation and systems integration. Marksmanship performance of eleven participants was assessed during live fire and simulator shooting scenarios while in firing positions and protective equipment that are known to have effects on performance. The consistency of the performance and performance differences observed across firing configurations and firing positions in this within-subjects study suggests that marksmanship simulator trainers are sensitive enough to provide valuable insights on performance interferences during CIE test and evaluation, while saving time and resources.

The effect of physical exertion in chemical and biological personal protective equipment on physiological function and reaction time

OBJECTIVES

The primary objective of this study was to describe and compare changes in heart rate, venous pH, venous partial pressure of carbon dioxide (pCO(2)), venous bicarbonate level, lactate level, oxygen saturation (SpO(2)), and tympanic membrane (TM) temperature occurring in a group of healthy volunteers during 20 minutes of physical exertion, both with and without chemical and biological personal protective equipment (PPE). A further aim was to establish whether any significant prolongation of reaction time occurred after physical exertion in chemical and biological PPE, compared to baseline values without the protective equipment.

METHODS

Nineteen highly fit volunteers were subjected to a baseline reaction time test and measurement of physiological variables. They were then subjected to physical exertion on a treadmill: once while wearing a short-sleeved t-shirt, shorts, and running shoes and once while wearing chemical and biological PPE. Repeat measurements of the physiological variables were made after 10 and 20 minutes of physical exertion in both groups, after which repeat reaction time tests were conducted.

RESULTS

Results showed that physical exertion of 20 minutes undertaken by highly fit volunteers wearing PPE resulted in a higher heart rate response and TM temperature compared with control measurements. Decreased venous pH and increased venous pCO(2) were also observed during exertion in the PPE group. Although differences in these variables between the control and PPE groups were statistically significant, they were not of clinical relevance in the sample of volunteers studied. No significant difference in reaction time before and after exertion in PPE was identified.

CONCLUSIONS

This study did not identify any effect of 20 minutes of heavy exercise in highly fit volunteers wearing level C chemical and biological PPE on reaction time. Heart rate response and TM temperature were higher during exertion in PPE. These differences, along with other physiological alterations observed, were not of clinical relevance. Further studies using arterial blood gas analysis and a more accurate measure of core body temperature are needed to better assess the physiological effect of this level and duration of exercise on subjects wearing similar PPE. Other aspects of cognition also require investigation under these conditions, in order to assess their effect on patient and rescuer safety.