1. Introduction
The COVID-19 pandemic currently represents a major global problem, with significant health, social and economic consequences. Indeed, the coronavirus has infected more than 15 million people, and more than half a million had died from the new disease by the end of 6 June 2020 [
1]. Since the numbers are still increasing [
1], countries’ policies proclaimed social isolation as an effective measure of combating the pandemic [
2]. In line with global efforts, between 19 March and 11 May, 2020, the Croatian Government adopted measures to restrict gathering in public places and parks, suspend public transportation, and close institutions. Besides all social gatherings, work in retail and services including sports activities were prohibited. People living in cities and urban areas seem to be the most affected by these measures, as they were obligated to stay at home and likely reduce their common activities. Reducing the PA level could have a negative health impact, even among healthy, uninfected people [
3].
Physical inactivity is one of the leading risk factors for developing numerous non-communicable diseases and shortening life expectancy [
4], and represents a large economic burden [
5]. What is more, physical inactivity seriously affects human physiology and leads to dysfunction in glucose homeostasis, a decrease in protein synthesis, muscle deinnervation, and poorer immune function [
6]. These health consequences are evident even after a few days of inactivity [
6]. Besides, decreasing PA levels in youth can have serious consequences on health status in older age. Generally, several determinants influence PA behavior, including sex, age, socioeconomic status (SES), and psychosocial factors (e.g., social support, attitudes, motivation, etc.) [
7,
8]. Some of these factors may likely boost or attenuate the general impact of the above social and spatial restrictions on PA level. In addition, routine activities—such as attending university lessons or working, spending time active, and participating in sport—are among the factors expected to moderate the level of habitual PA over the course of the pandemic in large cities [
9,
10,
11,
12,
13].
A number of commentaries, recommendation papers, and theoretical reviews have been written about the possible negative consequence of pandemic on one’s health [
3,
14,
15,
16]. Experts, scientists, and world health institutions are warning of the potential negative effect on health of physical inactivity as an indirect consequence of the COVID-19 quarantine [
3,
14,
15,
16]. A recent review highlights the potential consequence of inactivity and sedentarism due to the pandemic on cardiovascular, metabolic, and neuromuscular health [
6]. What is more, according to FitBit data, a 7% to 38% decline in step counts was noted during the week ending 22 March 2020 [
17]. Moreover, the amount of experimental research on this topic is increasing [
18,
19,
20]. Two recently published large-scale studies showed the negative impact of quarantine on PA levels in different populations [
19,
20]. In addition, several small-scale studies reported decreased PA levels in different populations after restrictions due to the COVID-19 lockdown [
21,
22,
23,
24]. However, some studies found that one section of active participants decreased their PA level, and that some inactive subjects tended to increase their PA level during lockdown [
21,
22,
23,
24]. These studies were performed on adolescents or older adults and did not examine factors that could possibly boost or attenuate (i.e., moderate) the change in the PA level in a homogenized group of young urban adults. However, more research is needed in this field to determine the potential consequences of restrictions in different populations. Therefore, this study aimed to investigate the moderators of change in PA level after 30 days (30-d) of restrictions due to the COVID-19 pandemic in young urban adults. Since the restriction measures disrupt these people’s everyday routines to the greatest extent, any change in their PA level could be likely affected by the presence or absence of habitual daily behaviors.
3. Results
The basic characteristics of the participants for MVPA (before and after restrictions), change in PA level, sport participation, and SES (before restrictions) are shown in
Table 1.
Figure 1 shows changes in MVPA between pre- and post-30-day restriction measures due to the COVID-19 pandemic in male and female, active and non-active, students and non-students, and between sport participants and non-sport participants.
There was no interaction between sex and time (F = 0.07, df = 1, p = 0.79), MVPA level decreased among girls by 64.8 min/day (p < 0.0001), while in boys MVPA level dropped by 57.7 min/day (p = 0.006) after lockdown. Significant activity x time interaction (F = 25.35, df = 1, p < 0.0001) indicates that activity status before the pandemics significantly moderated MVPA level during the restriction measures. Active participants decreased their MVPA level by 100.7 min/day (within-group effect: p < 0.0001), while participants who were non-active before lockdown increased their MVPA level after 30-d restrictions (increase of 48.9min/day, within-group effect: p = 0.051). Non-significant student status x time was shown (F = 10.51, df = 1, p = 0.29). The within-group effect was not evident in both groups (within students MVPA significantly decreased by 69.0, p < 0.0001) while for non-students a non-significant reduction of 35.0 min/day was evident, p = 0.22). Non-significant sport participation x time interaction was shown (F = 1.55, df = 1, p = 0.22). In sport participants, a marked reduction in MVPA level was observed (MVPA drop by 95.3, p = 0.001). While in subjects who did not participate in sport before restrictions, MVPA dropped by 54 min/day; p < 0.0001).
Table 2 shows the results of the multiple regression analysis for MVPApost. Regression analysis revealed that MVPApre has significant and positive effect on MVPApost (
β = 0.297,
S.E. = 0.056;
95% CI = 0.188, 0.406;
p < 0.0001) while other predictors have not reached statistical significance (
p = 0.592–0.993, see
Table 2).
4. Discussion
This study investigated the effect of different moderators of change in PA level among young adults after 30-d of restrictions during the COVID-19 pandemic. The results suggest that restriction measures equally affected the PA of both sexes as there was an evident drop in MVPA in both female, and male young adults. On the other hand, our results indicate that restriction measures affect previously active and inactive groups of young adults differently. More specifically, previously sufficiently active people decreased their MVPA level during the restrictions, while inactive people accumulated almost 50 min/day more MVPA during lockdown on average than before the epidemic). Finally, when we compared groups of students and non-students as well as sport participants and non-sport participants, the effects of 30-d restriction measures on MVPA duration tend to be the same in all of the groups.
Unsurprisingly, our results show that, overall, PA has decreased during restrictions, a finding that has also been reported in other similar recent studies [
22,
23,
24]. While other studies attributed this drop in PA to the limited ability for participation in organized sport due to restrictions imposed, the drop in MVPA in this study was similar in both youths that usually participated in organized sports and their peers that did not. On the other hand, this study indicates that prior PA status (active/non-active) is a significant moderator of change in MVPA during the 30-d of restrictions. It seems that participants who were insufficiently active prior to lockdown have managed to increase their MVPA during the 30 days of restrictions. This might be facilitated by a lower starting PA level of inactive youth as compared to their sufficiently active peers (25.0 min/day and 95.0 min/day, respectively). Nevertheless, the difficulties in introducing changes in PA behavior among the least active portion of the population are well known. Since lack of time is one of the most frequently reported barriers to exercise [
28], the increase in MVPA in inactive participants might be driven by the fact that, due to movement restrictions, people had more time for other activities (e.g., exercise). It has been repeatedly shown that inactive people gain great benefits from even a modest amount of PA compared to their active peers with regards to premature mortality [
29], the period of restrictions can represent a window of opportunity to introduce behavioral change to the portion of the population with the highest risk, and maximize benefits for public health. Still, an important question remains: ‘
Whether the acquired values of PA will be retained after the restrictions remission or will be the same and even lower as before lockdown?’ Although the answer to this question remains unanswered, we aim to conduct a follow-up study and try to gain a better understanding of this phenomenon. On the other hand, it would also be interesting to unravel the reasons why active people have difficulties in maintaining their PA level during the lockdown. We propose at least two possible explanations for this. First, sports facilities and sports parks and playgrounds were closed, which markedly reduced access to places for exercise. Second, participants who were active before the pandemic need much more physical space to engage in movement and activities, since their MVPA before the lockdown was much higher compared to their non-active peers.
Two similar studies have investigated levels of PA in active and inactive individuals, as well in male and female adults during the restrictions. Giustino et al. [
22] investigated levels of PA before and during the last seven days of the COVID-19 quarantine in the Italian active population (n = 802, mean age: 32.27 ± 12.81 y.o.). They found that the number of highly active participants dropped (26%, n = 193), and the number of low and moderately active subjects increased (19%, n = 200; and 7%, n = 409, respectively). In the same study [
22], both females and males decreased their total weekly energy expenditure, where males showed more reduction. The second study, performed by Lesser and Nienhuis [
21] examined the influence of restrictions on PA level and well-being in the Canadian population (mean age ± SD = 42 ± 15, n = 1098). Results of this study revealed that 22% of active participants decreased their PA and 37% did not change their PA level at all. However, among inactive participants, 33% become more active and 26% did not change their PA level after restrictions. Although the mentioned results are difficult to compare with the results of our study due to different methodologies used, we can see a drop in PA level among active subjects and increase in PA among non-active participants during restrictions. A recent study by Sekulic et al. [
23] examined the trends of changes in PA levels among 388 adolescents (mean age = 16 yrs) during restrictions in southern Croatia. This study found a significant drop in PA overall. However, when analyses were stratified by gender, the drop in PA level during restriction measures was seen in boys but not in girls. The findings from Sekulić et al. and Giustino et al. are not in accordance with our study considering the effect of sex on the change in PA due to restrictions. However, it is important to note that these studies used different methodologies and instruments for the assessment of PA, which severely limits comparability. In addition, the difference in populations that were studied can also potentially contribute to the difference in reported results (16 y.o. adolescents vs. 20-yo young adults vs. and 32 y.o. adults). In addition to small-scale research, two large-scale studies reported the effects of the COVID-19 lockdown on PA behavior. One recently published article examined whether the quarantine measures in the United Kingdom had disproportionate impacts on the intensity of PA in groups of people who are, or who perceive themselves to be, at higher risk from COVID-19 [
20]. The results of this study showed that doing less intensive PA during the quarantine was related to obesity, hypertension, lung disease, depression, and disability. Another large-scale study was published recently and included 35 research organizations from Europe, North-Africa, Western Asia, and America [
19], and showed that the COVID-19 quarantine had a negative effect on both VPA and MPA levels. In addition, many recommendations and theoretical papers have emphasized the importance of maintaining regular PA level and physical exercise during pandemic. It is important to note that a reduced PA level can have serious negative impacts in apparently healthy individuals [
6]. Therefore, exercise interventions along with a more general PA intervention need to be implemented immediately on the national level all around the world, both during and after the pandemic.
This study has several strengths. First, while most similar studies have used on-line surveys with convenience sampling, this study has investigated PA level during the COVID-19 pandemic in a subsample of a randomly selected cohort of young people, thus reducing the possibility of sample bias. Second, we considered several potential moderators of behavior change which had not been reported previously.
On the other hand, several limitations also need to be acknowledged. Firstly, PA was not measured, but was self-reported through a questionnaire, which typically leads to recall bias. Still, the SHAPES questionnaire used in this study has been previously shown to be a reasonably valid and reliable instrument for assessing PA [
26]. Moreover, the same instrument was used for the assessment of the change in PA duration after restriction measures. Secondly, the low response rate and consequently relatively small sample limit the ability to generalize our results. However, the participants of this study differ from the cohort members that could not be reached, and, therefore, this study lacks generalizability.
There are several implications of this study for subsequent research, policy and practice. The study was designed as an observational cross-sectional study investigating how different moderators of change in PA affect PA level during COVID-19 lockdown in young urban adults. Follow-up studies are needed to examine the long term consequences of the changes in PA level during lockdown. This research will be expanded by a follow-up study that will include the examination of the level of PA after the dissolution of restriction measures in previously active and non-active young urban adults. The study reveals that the 30-d of restrictions have equally affected young urban adults of both genders. PA status before the COVID-19 pandemic has moderated the level of MVPA during the restriction measures. The lockdown restrictions during the early wave of the pandemic in spring 2020 have affected active and non-active young urban adults differently. In particular, more active people decrease their MVPA level, while non-active people tend to increase their MVPA level during lockdown. These findings could be useful for different stakeholders to implement measures to prevent a decrease in PA in young urban adults during the pandemic. The promotion of regular PA is of particular importance for maintaining an adequate level of PA during lockdown in physically active and inactive individuals. Moreover, health promoting measures and preventive interventions during restrictions could represent an opportunity to improve the lifestyle behavior for inactive people. Finally, our results suggest that ensuring the possibility to safely conduct outdoor activities, and adapting equipped indoor training facilities, where possible, is of particular importance during public health restriction measures, especially for more active individuals, whose exercise requires more space and equipment.
In conclusion, this study examined the effect of different moderators of change in PA during the COVID-19 lockdown in a group of young adults. While the reduction in the duration of MVPA during lockdown was similar across sex, student status and prior participation in sport, baseline activity level was shown to be a significant moderator of change in MVPA. The finding that MVPA had markedly increased in previously insufficiently active individuals during lockdown deserves to be acknowledged by public health authorities in similar circumstances in the future, when measures to reinforce this positive behavior change will need to be introduced.
