Performance testing of an innovative telemetric temperature sensor in animals

Physical demands and physiological strain of American football referees while officiating

OBJECTIVES

Certain occupations are associated with greater risk of triggering a sudden cardiac event because of high levels of physical exertion and extreme thermal environments in which they occur. The extent to which sports officials--particularly high school (HS) American football referees--experience these conditions is unknown. Forty-six male HS officials (72% White/Caucasian; age = 48 ± 12 years, body mass index = 31.7 ± 6.6 kg·m^-2) were studied to quantify the physiological strain and physical demands of officiating.

METHODS

Referee demographics (e.g., experience, habitual exercise), pre-game urine specific gravity (U_SG), thermal (peak core temperature [T_core]) and cardiovascular (average heart rate [HR]) strain, kinematic activity (e.g., total distance, speed, mechanical intensity), and environmental conditions were measured during 10 regular season varsity HS football games (≈2.5 h each) in the Southeastern United States (average wet bulb globe temperature and relative humidity: 18.9 ± 6.0 °C and 78.2% ± 12.1%). Analyses included descriptive statistics, bivariate correlations, and linear regression.

RESULTS

Referees covered 5.2 ± 1.2 km per game, eliciting average HR and peak T_core of 71.5% ± 8.0% HR_max and 38.3 ± 0.5 °C, respectively; 38% began games dehydrated (U_SG = 1.026 ± 0.004). Multiple regression analyses revealed that obesity (β = 0.34), not participating in regular exercise (β = -0.36), and officiating at lower mechanical intensity (β = -0.33) predicted greater cardiovascular strain (all p ≤ 0.03). White/Caucasian race/ethnicity (β = 0.59), younger age (β = -0.46), and obesity (β = 0.28) predicted greater thermal strain (all p ≤ 0.01).

CONCLUSION

HS football referees experienced elevated levels of physiological strain while officiating, with individual factors modulating the magnitude of strain. Strategies aimed at reducing obesity, increasing exercise participation, and improving cardiovascular health should be emphasized to mitigate strain and prevent cardiac events.

Validation of an ingestible temperature data logging and telemetry system during exercise in the heat

Aim: Intestinal temperature telemetry systems are promising monitoring and research tools in athletes. However, the additional equipment that must be carried to continuously record temperature data limits their use to training. The purpose of this study was to assess the validity and reliability of a new gastrointestinal temperature data logging and telemetry system (e-Celsius™) during water bath experimentation and exercise trials. Materials and Methods: Temperature readings of 23 pairs of e-Celsius (T_eC) and VitalSense (T_VS) ingestible capsules were compared to rectal thermistor responses (T_rec) at 35, 38.5 and 42°C in a water bath. Devices were also assessed in vivo during steady-state cycling (n = 11) and intermittent running (n = 11) in hot conditions. Results: The water bath experiment showed T_VS and T_eC under-reported T_rec (P<0.001). This underestimation of T_rec also occurred during both cycling (mean bias vs T_VS: 0.21°C, ICC: 0.84, 95% CI: 0.66–0.91; mean bias vs. T_eC: 0.44°C, ICC: 0.68, 95% CI: 0.07–0.86, P<0.05) and running trials (mean bias vs. T_VS: 0.15°C, ICC: 0.92, 95% CI: 0.83–0.96; mean bias vs. T_eC: 0.25, ICC: 0.86, 95% CI: 0.61–0.94, P<0.05). However, calibrating the devices attenuated this difference during cycling and eliminated it during running. During recovery following cycling exercise, T_eC and T_VS were significantly lower than T_rec despite calibration (P<0.01). Conclusion: These results indicate that both T_eC and T_VS under-report T_rec during steady-state and intermittent exercise in the heat, with T_eC predicting T_rec with the least accuracy of the telemetry devices. It is therefore recommended to calibrate these devices at multiple temperatures prior to use.

Theoretical and Experimental Studies of Epidermal Heat Flux Sensors for Measurements of Core Body Temperature

Long-term, continuous measurement of core body temperature is of high interest, due to the widespread use of this parameter as a key biomedical signal for clinical judgment and patient management. Traditional approaches rely on devices or instruments in rigid and planar forms, not readily amenable to intimate or conformable integration with soft, curvilinear, time-dynamic, surfaces of the skin. Here, materials and mechanics designs for differential temperature sensors are presented which can attach softly and reversibly onto the skin surface, and also sustain high levels of deformation (e.g., bending, twisting, and stretching). A theoretical approach, together with a modeling algorithm, yields core body temperature from multiple differential measurements from temperature sensors separated by different effective distances from the skin. The sensitivity, accuracy, and response time are analyzed by finite element analyses (FEA) to provide guidelines for relationships between sensor design and performance. Four sets of experiments on multiple devices with different dimensions and under different convection conditions illustrate the key features of the technology and the analysis approach. Finally, results indicate that thermally insulating materials with cellular structures offer advantages in reducing the response time and increasing the accuracy, while improving the mechanics and breathability.

On the importance of telemetric temperature sensor location during intraperitoneal implantation in rats

This study aims to assess the thermal homogeneity of the intraperitoneal (IP) cavity and the relevance of using a fixed telemetric temperature sensor at a given location in studying rodents. Ten rats were intraperitoneally implanted with three Jonah® capsules each; after assessing the accuracy and reliability of the sensors. Two capsules were attached, one to the right iliac fossa (RIF) and the other to the left hypochondrium (LH), and another was placed between the intestines but not attached (Free). In the ex vivo condition, the differences between sensors and reference values remained in the range of ±0.1. In the in vivo condition, each sensor enabled the observation of temperature patterns. However, sensor location affected mean and median temperature values while the rats were moving freely. Indeed, temperature data collected in the LH were 0.1 significantly higher than those collected in the RIF and temperature data collected in the LH were 0.11 significantly higher than those collected with the Free capsules. In in vivo conditions, intra-sensor variability of temperature data was not affected by sensor location. Taking into account sensor accuracy, similar intra-sensor variability, and mean differences observed between the three locations, the impact of sensor location within the IP cavity could be considered negligible. In in vivo conditions, temperature differences between locations regularly exceeded ±0.2 and reached up to 2.5. These extreme values could be explained by behavioral factors such as food or water intake. Finally, considering the good thermal homogeneity of the IP cavity and possible adverse consequences of sensor attachment, it seems better to let sensors range free within the cavity.