The effect of the lowest heat stress limit conditions on psychomotor parameters in soccer players

Study aim: This study aimed (i) to describe psychomotor parameters for different temperature and humidity conditions, and (ii) to verify whether conditions at the borderline between some and great thermal discomfort on the humidex scale affect psycho-motor parameters in soccer players.

Material and methods: Twenty-four male soccer players aged 21.02 ± 3.22 years from a Polish 4th league club performed a graded treadmill running exercise test. Directly before the test and during the break after each load, blood was collected to determine lactate concentration ([LA]) and serotonin concentration (SER). The heart rate (HR), pulmonary ventilation (Ve) and oxygen up-take (VO₂) were recorded and the psychomotor test was performed. Measurements were carried out: (1) at rest, (2) at the lactate threshold (T_[LA]), (3) at the threshold of psychomotor fatigue (T_PF), and (4) at maximum intensity. Percentage differences between maximum intensity (100%) and the values of the tested parameters recorded at the T_[LA] and T_PF were also calculated. The tests were conducted in a climatic chamber at an ambient temperature of 28.5°C, with a relative air humidity of 58.7%.

Results: It was confirmed that the T_PF, which reflects the highest efficiency of the central nervous system, occurs at a higher running speed than the T_[LA]. For practical application, it was found that at the HSL, the T_PF occurs at: 84% of maximum running speed, 52% of maximum [LA] concentration, 93% SER_max, 91% HR_max, 73% VE_max, 84% VO_2max.

Conclusion: Understanding the psychomotor and physiological responses of soccer players at the borderline between some and great thermal discomfort (on the humidex scale) can support coaches in optimizing training sessions to prepare players for playing in more challenging climatic conditions.