Main findings
This study found that PA, whether measured as METs of PA or exercise behavior, was significantly correlated with physical fitness. Specifically, both are positively correlated with cardiorespiratory endurance performance, while exercise behavior are additionally positively correlated with flexibility and muscular fitness. However, neither is related to body composition. Furthermore, PA-METs and exercise behavior exert an interacting effect on physical fitness. In addition, this study found that work-related PA may exert a negative effect on physical fitness.
1. PA-METs and exercise behavior with health-related physical fitness
This study measured PA using METs and exercise behavior and investigated the relationship between PA and physical fitness. Individuals with sufficient PA-METs displayed significantly better cardiorespiratory endurance performance than those with inadequate METs. In terms of exercise behavior, the flexibility and cardiorespiratory endurance of regular exercisers are better than those without exercise. Therefore, PA-METs and exercise behavior clearly positively influenced cardiorespiratory endurance. This result is consistent with those of many studies (e.g., Anton, Duncan, Limacher, Martin, & Perri, 2011; Franklin, Eijsvogels, Pandey, Quindry, & Toth, 2022; Myers, Kokkinos, Arena, & LaMonte, 2021). The mechanisms of the effects of exercise and PA on cardiovascular health include changes that improve maximum output per beat, which, in turn, provides greater oxygen delivery and enhances vasodilatation (Hellsten & Nyberg, 2011). In terms of flexibility, the study found that it was related to exercise behavior but not to the PA-METs. Flexibility is a comprehensive expression of joints and muscle groups; thus, it can be improved through body movement and muscle extension.
1. Regular exercisers may display a more significant positive effect on flexibility due to the higher frequency of body movements over a larger range of motion (Cornelius, 1990).
In addition, this study combined different categories of exercise behavior and PA-METs to examine the interaction effects of exercise behavior and PA-METs on physical fitness. We found that (1) regular exercise is beneficial to cardiorespiratory endurance even if the PA-METs is insufficient; (2) even with regular exercise if the PA-METs are insufficient, the muscular fitness is significantly worse than that of those who with a sufficient amount; (3) those without exercise exhibited significantly poor flexibility regardless of whether or not their PA-METs are sufficient; (4) BMI is not correlated with exercise behavior and PA-METs.
2. Regular exercise is beneficial to cardiorespiratory endurance even if the PA-METs are insufficient.
The study found that for individuals with insufficient PA-METs, those without exercised displayed the worst cardiorespiratory endurance; however, their cardiorespiratory endurance performance did not differ significantly from the reference group as long as they observed exercise behavior (whether or not such behavior are regular). A possible reason for this result is that people with insufficient PA-METs tend to have a sedentary lifestyle (Ekelund et al., 2016), as the WHO (2023) recognizes physical inactivity as an important risk factor of non-communicable diseases. Therefore, as long as people engage in exercise, it is beneficial for cardiorespiratory fitness (Piercy et al., 2018).
3. Even with regular exercise, if the PA-METs are insufficient, then muscular fitness is significantly worse than those with sufficient PA-METs.
In terms of muscular fitness, PA intensity is more important. Muscular strength training is based on the does–response effect. In other words, the number of neurons activated at the site of movement to produce the number of contracted muscle fibers determines muscle strength. Therefore, the intensity of weight training becomes a necessary condition for resistance training: by loading the muscle groups with high-intensity exercise, more motor neurons are activated, and the corresponding stimulated muscle fibers are activated. Clearly, PA intensity is the key factor in the production of muscle strength, and if it does not reach the threshold of response, then muscular strength will not improve (Faigenbaum et al., 1999). For this reason, the results of the current study demonstrated that muscular fitness among individuals with insufficient PA-METs is significantly worse than those with sufficient PA-METs even with regular exercise.
Those without exercise displayed significantly poor flexibility regardless of whether or not their PA-METs are sufficient.
The results illustrated that individuals with sufficient PA-METs but without exercise exhibited poor flexibility, which is similar to the result of Lin et al. (2022). The possible reasons for this result are that people who are physically active but do not exercise are likely to be manual laborers, who frequently undergo brief periods of repetitive resistance PA. As such, they are vulnerable to fatigue, stiffness, and pain, which may affect flexibility (Balaguier et al., 2017), or to the lack of sufficient rest and recovery time (Fleck, 1999).
PA-METs and exercise behavior were not significantly correlated with BMI.
The study found no significant correlation among exercise behaviors, PA-METs, and BMI, regardless of whether or not the independent or combined variables were considered. This finding suggests that PA alone may be ineffective for long-term weight control and that it should be combined with dietary and lifestyle modification. (Annesi & Eberly, 2022). In fact, including psychological factors in weight management strategies may be beneficial (Lambert et al., 2019).
Comparison of the GPAQ and a single question to measure exercise behaviors
GPAQ is a tool that measures PM by and considers work, transportation, and leisure. It has good reliability and validity (Adiguzel et al., 2021; Doyle et al., 2019; Rudolf et al., 2020) and is applicable to different ethnic groups. Along with gender, age group, and occupational type (Adiguzel et al., 2021), data can be collected through a self-report or interview (Rudolf et al., 2020). The GPAQ seemingly implies the assumption that “the benefits (positive or negative) of PA during work, transportation and leisure time are the same.” However, exercise has a psychologically active and positive meaning due to its planned, structured, and repetitive nature (Caspersen et al., 1985), which makes it different from ordinary physical activities (e.g., PA-METs as measured by the GPAQ). On the basis of the findings, the study identifies three distinctions between PA-METs measured by the GPAQ and exercise behaviors measured by the single question as follows.
First, using the GPAQ as a measurement instrument for PA will simultaneously underestimate the health benefits of exercise and overestimate the benefits of PA at work, especially for high-intensity laborers (Holtermann, Schnohr, Nordestgaard, & Marott, 2021). Therefore, when using the GPAQ to evaluate PA-METs, consideration should be given to whether or not the proportion of PA at work is excessive.
Second, when PA-METs use the total METs of PA as the index, it does not adequately reflect the concept that “PA should have the appropriate frequency, intensity, and duration to be health-beneficial.” For example, weekend warriors (Lee, Sesso, Oguma, & Paffenbarger Jr, 2004) are busy during the week and do not maintain a regular exercise routine. Therefore, they can only demonstrate that they spend time diligently for their health by exercising for longer durations on holidays. Nonetheless, excessively concentrated exercise time and intensity can easily result in acute sports injuries, which is unhealthy (Delimaris, 2014). Therefore, although the PA-METs measured by the GPAQ are a simplified PA index, cautious discussions should be held regarding the obtained results (Keating et al., 2019).
Finally, the “single question to measure exercise behavior” only asks about the presence and regularity of exercise behavior. Although it focuses on exercise and saves time in answering, it ignores non-exercise physical activities and exercise intensity. Furthermore, as revealed by the finding, even regular exercise produces very limited health benefits if it lacks sufficient intensity.
In summary, although the choice of the multiple-question GPAQ or the single question for measuring exercise behavior can be determined according to the objective of the study and the needs of research implementation, scholars should focus on integrating the advantages of the two aspects as the measurement of PA in the future to better understand the relationship between PA and health.