Exergy efficiency on incremental stationary bicycle test: A new indicator of exercise performance?

Abstract

The first and second laws of the thermodynamics were applied to the human body to evaluate the performance of subjects under different training levels. Ten cyclists were evaluated in the stationary bicycle with the indirect calorimetry analysis to obtain the metabolism on an energy and exergy basis. A distinguishing feature of this article is the evaluation of the exergy efficiency of the body with the knowledge of the real performed power and the internal temperature (measured tympanic temperature and calculated esophagus temperature). Regarding the skin temperature, an infrared camera was used to measure different parts of the body. Therefore, the phenomenological behavior of the body was assessed and used as a basis to apply the exergy analysis. Results indicate that the destroyed exergy can be an indicator of performance when compared with maximum oxygen consumption. Nevertheless, more experiments must be carried out to proper state if there is a correlation. Eventually, the exergy efficiency was calculated for all subjects, and its value was around 23 to 28%.

Behavior of skin temperature during incremental cycling and running indoor exercises

“…The anthropometric characteristics of the individuals, maximum oxygen consumption are in Table 1 . This manuscript is a logical progression of work developed by the research group, where each method is available in [ 4 , 5 ].…”

“…Figure 1 shows an example of the experiment. A more precise description can be seen in references [ 4 , 5 ]

Figure 1 Protocol used for both tests: (a) running; (b) cycling.

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“…The body has sensors located at the skin's surface and deeper areas, e.g., the hypothalamus that detects environmental and physiological modifications [ 3 ]. A control system maintains the body in a narrow range of temperatures to function accordingly for different environmental temperatures, activity levels, or pathologies [ 4 , 5 ].…”

“…Moreover, few articles in the literature correspond the skin temperature with physiological variables such as metabolism and oxygen consumption for the same subject during two different tests. redFinally, to properly apply the second law of thermodynamics to the human body, it is necessary to evaluate both physical activities, since in cycling tests, there is an easiness to calculate the performed work [ 4 ], and on the treadmill, the heat and mass exchange phenomena are more prominent [ 5 ]. This purpose is in agreement with the reasoning proposed by [ 7 ].…”

Comparative Analysis of the Indirect Calorimetry and the Metabolic Power Method to Calculate Energy Expenditure in Team Handball

“…For example, EE has been obtained via indirect calorimetry (EE Spiro ), often considered as the gold standard for the calculation of EE, to compare the effects of different shoe materials during running [4]. EE Spiro analyses has also been applied in cycling to assess the metabolism on an energy and exergy basis [5]. In sports that are based on acyclic movements (e.g., team sports), the assessment of EE is controversially discussed, and spiroergometry is often unfeasible in competition and/or training [6].…”