Single Effort in Air Temperature of Minus 10°C Changes the Erythrocyte Aggregation Indicators in Young Healthy Men

2.1 Study group characteristics The study involved 30 healthy males, students of the University of Physical Culture in Krakow, Poland, faculty of physiotherapy. Their mean body height was 178.9 ± 6.5 cm, mean body mass equaled 76.8 ± 11.3 kg. After the subjects were assigned to each group, the average body height in the experimental group (177.9 ± 5.9 cm) and in the control/neutral group (179.9 ± 7.2 cm) was calculated. The average body mass in the experimental group (73.1 ± 6.6 kg) was lower than that in the control group (81.2 ± 14.1 kg).

Simple randomization with a 1:1 allocation ratio served to randomly assign the participants to the experimental or control group. This was done before the first blood sampling, with the randomization sequence generated prior to the study. No stratification factors were used. The participants in the experimental group performed physical exertion under the conditions of low temperature (-10°C). The workout was undertaken in a thermal climate chamber in the Laboratory for Climate Technology Research and Heavy Duty Machines, Cracow University of Technology in Krakow. The thermal climate chamber meets the requirements of the PN-EN ISO/IEC 17025:2005 standard and possesses an accreditation certificate No. AB 1678, issued by the Polish Centre for Accreditation. The Laboratory for Climate Technology Research and Heavy Duty Machines is a research center accredited in the field of defense and security by the Minister of National Defense (accreditation No.: 55/MON/2018). The control group, in turn, performed the same physical effort but in the open air, in thermoneutral conditions (the air temperature was 18.1°C on the day of the study).

The experiment comprised 3 stages: (1) Before the exercise, blood samples were taken from the participants. This was performed in the morning hours on 11 May 2024 at the Blood Physiology Laboratory of the Central Research and Development Laboratory, University of Physical Culture in Krakow. (2) Both groups undertook an exertion test. (3) Blood samples were collected from all participants again after the exercise.

The study followed the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of the Regional Medical Chamber in Krakow, Poland 2.2 Research method A two-factor experimental design with repeated measures was employed in the study. Ambient temperature (low vs. thermoneutral) constituted the between-subject factor; time of measurement (pre- and post-exercise) was the within-subject factor. The study followed the design of an exploratory investigation. In the group allocation of the participants, the principle of double randomization was employed. In experimental research, where a phenomenon is induced by the researcher on purpose, its course is observed in a planned and controlled way. Therefore, the influence of particular factors on the studied parameters can be assessed. Conclusions are drawn on the basis of the discovered relationships; the accuracy of the conclusions is evaluated with a specific probability. In the present study, a significance level of α = 0.05 was assumed, corresponding to a 95% confidence level.

2.3 Parallel group technique The participants were randomly allocated to the experimental group and the control group; the double randomization principle was followed. The first measurement preceded introducing the experimental factor.