The COVID-19 pandemic has changed the way many people live. To assess its impact on sleep quality and quantity, blue light exposure, and the mental health of Polish university students, a cross-sectional survey was conducted. Almost half of the participants were medical students (47.62%; n = 630). The majority of students were suffering from insomnia (58.13%, n = 769). Almost every third student was sleeping less than 7 h a day (30.39%, n = 402). Our study showed that a short sleep duration correlates with poorer mental health outcomes. Respondents who declared sadness and depression were more likely to suffer from insomnia (OR = 5.6997, 95% CI: 4.3641–7.4441). Difficulty with tasks was also more likely to co-occur with insomnia (OR = 5.4723, 95% CI: 4.3007 to 6.9630). The results of this study showed that the COVID-19 pandemic contributed to the deterioration of sleep quality and quantity as well as the psychological well-being of Polish students. It is important to take steps to promote proper sleeping habits to alleviate the risk of mental health disorders in this group of people.

The COVID-19 pandemic and imposed restrictions were strong stress factors for young people, especially students. Increased alcohol consumption, smoking cigarettes, usage of heated tobacco products, and other stimulants are common methods of coping with anxiety. However, they can have serious negative health effects. A survey consisting of 12 questions related to mental health and psychoactive substance taking habits was distributed among Polish students between 22 February 2021 and 3 April 2021. A total of 1323 participants met all inclusion criteria (nfemales = 1021, nmales = 297, nother gender = 5). The mean age was 22 years old (±4.17); 47.62% were medical university students. A total of 71.92% reported negative impact, 8.25% did not notice changes, and 12.58% declared a positive pandemic impact on their mental health. A total of 12.58% declared an increase, 70.22% did not see any differences, and 17.20% reported a decrease in their psychoactive substance usage tendency due to the pandemic. Worse perceived psychologic well-being was correlated with a higher tendency to use tobacco (p < 0.001) and alcohol (p < 0.001), and not with marijuana and products containing tetrahydrocannabinol (p = 0.136), and hard drugs (p = 0.799). The majority of participants declared a negative pandemic impact on mental health and did not report significant changes in psychoactive substance taking habits. Medical personnel should be aware of the current situation and apply for proper prevention and treatment programs.

The restrictions implemented to prevent the spread of the SARS-CoV-2 virus have impacted the majority of life domains. To evaluate their potential consequences on physical activity (PA) and dietary habits among Polish undergraduates, a survey consisting of the IPAQ-SF, authors’ questions based on the Polish National Institute of Public Health recommendations, and authors’ questions scaled −5/0/5 on personal opinion was created and administered between 22 February and 3 April 2021. A total of 1323 students met the study conditions (1021 females, 297 males, 5 did not specify gender, mean age: 22 years old (SD = 4), mean BMI = 22.27 kg/m2 (SD = 3.87)). A total of 27.21% of students were in the low, 48.53% in the moderate, and 24.26% in the high PA group. A total of 71.94% estimated that the pandemic had a negative impact on their PA, 8.16% no impact, and 19.9% a positive impact. A total of 35.5% had an insufficient intake of vegetables, 34.3% declared adding salt to meals, and 31.6% ate animal-based products the majority of days in a week or every day. A total of 51.02% assessed the impact of the pandemic on their nutrition as negative, 20.11% did not notice changes, and 28.87% reported a positive impact on their dietary habits. Most of the students saw harmful pandemic effects on their diet and PA compared to the times before restrictions. This can lead to a higher prevalence of non-communicable diseases (NCDs) in the future.

Cardiopulmonary exercise testing (CPET) is the method of choice to assess aerobic fitness. Previous research was ambiguous as to whether treadmill (TE) and cycle ergometry (CE) results are transferrable or different between testing modalities in triathletes. The aim of this paper was to investigate the differences in HR and VO2 at maximum exertion between TE and CE, at anaerobic threshold (AT) and respiratory compensation point (RCP) and evaluate their association with body fat (BF), fat-free mass (FFM) and body mass index (BMI). In total, 143 adult (n = 18 female), Caucasian triathletes had both Tr and CE CPET performed. The male group was divided into <40 years (n = 80) and >40 years (n = 45). Females were aged between 18 and 46 years. Body composition was measured with bioelectrical impedance before tests. Differences were evaluated using paired t-tests, and associations were evaluated in males using multiple linear regression (MLR). Significant differences were found in VO2 and HR at maximum exertion, at AT and at RCP between CE and TE testing, in both males and females. VO2AT was 38.8 (±4.6) mL/kg/min in TE vs. 32.8 (±5.4) in CE in males and 36.0 (±3.6) vs. 32.1 (±3.8) in females (p < 0.001). HRAT was 149 (±10) bpm in TE vs. 136 (±11) in CE in males and 156 (±7) vs. 146 (±11) in females (p < 0.001). VO2max was 52 (±6) mL/kg/min vs. 49 (±7) in CE in males and 45.3 (±4.9) in Tr vs. 43.9 (±5.2) in females (p < 0.001). HRmax was 183 (±10) bpm in TE vs. 177 (±10) in CE in males and 183 (±9) vs. 179 (±10) in females (p < 0.001). MLR showed that BMI, BF and FFM are significantly associated with differences in HR and VO2 at maximum, AT and RCP in males aged >40. Both tests should be used independently to achieve optimal fitness assessments and further training planning.

Cardiopulmonary exercise testing (CPET) is the method of choice to assess aerobic fitness. Previous research was ambiguous as to whether treadmill (Tr) and cycle ergometry (CE) results are transferrable or different between testing modalities in triathletes. The aim of this paper was to investigate the differences in HR and VO2 at maximum exertion and at anaerobic threshold (AT) and respiratory compensation point (RCP) and evaluate their association with body fat (BF), fat free mass (FFM), and body mass index (BMI). 143 adult (n = 18 female), amateur, Caucasian triathletes had both Tr, and CE CPET performed. The male group was divided into < 40 years (n = 80) and > 40years (n = 45). Body composition was measured with bioelectrical impedance before tests. Differences were evaluated using paired T-tests and associations were evaluated in males using multiple linear regression (MLR). Significant differences were found in VO2 and HR at maximum exertion, at AT and at RCP between CE and Tr testing, in both males and females. VO2AT was 38.8(± 4.6) ml/kg/min in Tr vs 32.8(± 5.4) in CE in males and 36.0(± 3.6) vs 32.1(± 3.8) in females (p < 0.001). HRAT was 149 (± 10) bpm in Tr vs 136 (± 11) in CE in males and 156 (± 7) vs 146 (± 11) in females (p < 0.001). VO2max was 52 (± 6) ml/kg/min vs 49 (± 7) in CE in males and 45.3 (± 4.9) in Tr vs 43.9 (± 5.2) in females (p < 0.001). HRmax was 183 (± 10) bpm in Tr vs 177 (± 10) in CE in males and 183 (± 9) vs 179 (± 10) in females (p < 0.001). MLR showed that BMI, BF and FFM are significantly associated with differences in HR and VO2 at maximum, AT and RCP in males aged > 40. Both tests should be used independently to achieve optimal fitness assessment and further training planning.