The results presented here indicate that among a population of healthy male subjects between 20 and 40 years, self-reported LTPA (MET-h/week) associated with better work ability, particularly in subjects with more physically demanding jobs. Furthermore, the results indicate that when exposed to different OPA levels, higher LTPA levels were positively associated with WAI. More specifically, LTPA had a significantly greater relationship between WAI in subjects with physically demanding jobs than in subjects with more sedentary jobs. This association was independent of age, BMI, alcohol consumption, working class status, and employment years.
Previous findings
Our findings are consistent with the systematic review of van den Berg et al. (
2009), which describes a strong association between absence of vigorous LTPA and WAI in an adult population. Furthermore, LTPA has a positive relationship with WAI among a cohort of mostly female health care workers (Arvidson et al.
2013). There is also evidence from a randomized controlled study that physical exercise intervention improves work ability due to enhanced cardiorespiratory fitness (Kettunen et al.
2014). Moreover, evidence from a cross-sectional study revealed an association between high LTPA levels and better work ability in workers with physically demanding jobs (Calatayud et al.
2015). However, this study was conducted on middle-aged participants and a more heterogeneous population with different PA and work ability measurement methods. Information on combined associations of LTPA and work ability in different occupational physical demands is currently limited, particularly in young adult men.
Interpretation of principal findings
In our study, the greater relationship between high LTPA and excessive OPA in work ability could be partially explained by the maintaining and improving effects of LTPA on cardiorespiratory fitness and health, which is normally included with voluntary movement and a sufficient amount of recovery time (Warburton et al.
2006). In contrast, OPA has been considered to have longer periods and lower intensity levels of maximal aerobic capacity, while elevating the 24-h heart rate and blood pressure, which may even impair cardiovascular health (Korshøj et al.
2015; Holtermann et al.
2018). In the present study, high levels of LTPA could also play a part in improving the responsiveness and adaptation of cardiovascular health and heart rate recovery (Lamberts et al.
2010). Since excessive periods of high OPA are reported to prolong high heart rates, high OPA and low cardiorespiratory fitness could cause cardiovascular strain that may lead to cardiovascular disorders. Higher cardiovascular fitness could possibly prevent these outcomes (Korshøj et al.
2015; Holtermann et al.
2016) and thus, appear in individuals with less illnesses, sick days and overall better work ability. Additionally, LTPA has been shown to decrease the risk for long-term sickness absence (LTSA), whereas OPA has been shown to increase the risk for LTSA (Holtermann et al.
2012). Moreover, LTPA has previously associated with fewer disability pensions because of musculoskeletal disorders (Fimland et al.
2015). Our study showed that the number of sick days linearly decreased with increasing LTPA MET tertiles.
As higher LTPA is associated with better physical and musculoskeletal fitness (Warburton et al.
2006), higher LTPA could be beneficial for those who are exposed to physical workloads including heavy lifting with static and constrained postures and activities, possibly impairing physical health functioning (Holtermann et al.
2012; Mänty et al.
2015). In our study, the positive association of LTPA could appear in the form of better self-assessed work ability, particularly in subjects with physically demanding jobs. On the other hand, it could also refer to better pain self-efficacy (Denison et al.
2007) strategies or other health-enhancing effects in relation to intensity, duration, or type of contraction caused by LTPA (Søgaard and Sjøgaard
2017). These effects could help more physically active participants to cope and adapt with the physical demands of high OPA (Holtermann et al.
2018). In our study, this could explain the inverse linear relationship across MET tertiles and the incidence of general pain, lower back pain, neck pain, and upper limb pain. In addition, individuals with low self-efficacy due to pain-concentrated disorders are reported to have a high probability of avoiding PA in their daily routines (Rejeski et al.
1998). The terminology of musculoskeletal disorders (MSD) is considered as a broad term covering any nonspecific disorder characterized by pain or decreased functioning (Søgaard and Sjøgaard
2017). Therefore, because of the possibly lower muscular health level in the lower PA group, lower WAI scores and higher pain incidence could indicate functional impairments in the future.
In addition, our study presented a smaller but significant relationship between lower OPA levels and LTPA. Nawrocka et al. (
2017) found a relationship between achieving recommended LTPA levels and WAI among white-collar workers. In the present study, even though the majority of participants were blue-collar workers, our results indicated a similar relationship in the group that had the lowest OPA level. Other studies have shown that sedentary workplace behavior combined with low LTPA is associated with work-related fatigue, musculoskeletal pain, and a higher risk for heart failure or burnout (de Vries et al.
2017; Naczenski et al.
2017). In the present study, higher LTPA and musculoskeletal fitness could particularly reduce work-related pain in the lowest OPA group, which is caused by time spent in unnatural and static or standing positions (Coenen et al.
2016). Such pain reduction could relate to better WAI.
In the present study, the participants were men of 20–40 years who had good work ability and were expected to have many employment years in the course of their career. However, the risk of subsequent retirement due to disability and mortality associated with lack of PA is expected to increase in middle age (Lear et al.
2017). Our current study revealed an inverse linear relationship between LTPA and working years, meaning that subjects that had more years under employment were also less physically active. In addition, the positive relationship between work ability and LTPA, particularly at the highest OPA, could be considered noteworthy as we have previously observed that participants who recorded the greatest share of their PA from work (61%) had, in contrast, the lowest level of LTPA (16%) (Päivärinne et al.
2018). Our present study adds value to our previously reported importance of LTPA, particularly in occupations that are physically demanding. As reported previously, individual factors (such as aging and lack of PA) may be associated with midlife transition and an increased risk of retirement due to disability (Lahti et al.
2016).
Strengths and limitations
Our study has several strengths. We used validated and widely employed questionnaires, such as the IPAQ long form to calculate LTPA and occupational PA along with the WAI. Our data were collected and analyzed from a random, homogeneous sample of young adult men, which allowed us to make reliable generalizations. We also recruited a relatively large sample of young Finnish adult men. However, there are limitations that should be taken into consideration. Due to the cross-sectional design of the study, the exposure and outcome are simultaneously assessed and, therefore, it is not possible to establish a true cause-and-effect relationship. Second, the subjective method of self-assessing LTPA and WAI may have resulted in reporting bias that could affect the outcome. Third, caution is advised when generalizing these results to women.