Job performance is defined as employees’ behaviors at work that support organizational goals (Motowildo et al., 1997). In this article, we focus more specifically on task performance, which refers to “behaviors that are recognized by formal reward systems and are part of the requirements as described in job descriptions” (Williams and Anderson, 1991). Factors that predominantly account for differences in static job performance are relatively stable constructs like abilities, knowledge, experience, and non-cognitive traits like personality (Sonnentag et al., 2008). In the analysis of job performance, within-person variance has largely been treated as measurement error (Dalal et al., 2014). However, as postulated by the theory of dynamic performance (Beal et al., 2005), job performance is determined by stable and transient factors, such as day-specific job demands, resources and personal energy levels. Indeed, within-person fluctuations can explain approximately 50% of the variation in job performance (Podsakoff et al., 2019; McCormick et al., 2020).

In their model of dynamic performance, Beal et al. (2005) propose that resource allocation to the task and the direction of one’s attention to the task are central for momentary performance. This requires self-regulatory resources that are not stable but may fluctuate over time. Studies have argued that internal states comprising energy indicate that self-regulatory resources are available at a specific time, which leads to better performance (e.g., Vahle-Hinz et al., 2021). Energy is a sense of positive affective arousal, which includes an eagerness and capability to act (Quinn and Dutton, 2005). It is a concept involved in many motivational theories (Schippers and Hogenes, 2011), as research has shown that highly energized employees tend to be more motivated (Butt et al., 2020) and get work done – resulting in higher productivity (Chen et al., 2016).

To capture employees’ energetic resources, we focus on vigor as a much-studied concept, that captures the energy specifically directed at work and that may vary from episode to episode like job performance (Reis et al., 2016). Vigor is characterized by “high levels of energy and mental resilience while working, the willingness to invest effort in one’s work, and persistence even in the face of difficulties” (Schaufeli et al., 2006). It is one of three constitutive aspects of work engagement, reflecting a positive, fulfilling affective-motivational state of work-related well-being (Schaufeli et al., 2002).

Various studies have demonstrated the fundamental role of the current level of vigor for daily job performance. On a between-person level, Carmeli et al. (2009) have shown that vigorous employees tend to perform better according to supervisor ratings. At a within-person level, this relationship has not been studied decisively. However, related constructs indicating the energetic state have been found to predict task performance at a within-person level, for example, recovery state (Binnewies et al., 2009), fatigue (Dettmers et al., 2020), or the hourly measured energy level (Vahle-Hinz et al., 2021). We therefore propose Hypothesis 1:

Considering personal energy as a critical, limited resource that positively influences daily job performance and can become depleted (Parker et al., 2021), it is essential to explore the incremental impact of other internal states on job performance. Specifically, understanding the interaction between vigor and other internal states and how job performance is affected when vigor is low, is crucial. We focused on mindfulness as an internal state whose key feature is the self-regulation of attention (Good et al., 2016) and leads to higher functioning at work (Glomb et al., 2011). Therefore, we argue that it might be capable of buffering detrimental influences of low energetic states on momentary performance.

Mindfulness is a state of non-judgmental attentiveness and awareness of what is taking place in the present moment, internally and externally (Brown et al., 2007). One way to view mindfulness is as a personal resource that assists people in managing demands by directing their attention on the present moment rather than issues outside of their control (Grover et al., 2017). It has gained increasing attention in the context of work and organizational psychology (van Dam et al., 2018) as research on mindfulness has shown beneficial effects for employee health and performance (Lomas et al., 2017; Mesmer-Magnus et al., 2017). Workplace mindfulness has mainly been studied as a stable personality trait (e.g., Lyddy et al., 2021) or as a skill that can be trained through interventions (for a review, see Creswell, 2017). However, it has been repeatedly argued that mindfulness is at its core a state that naturally fluctuates from moment to moment within persons (state or daily mindfulness; Forjan et al., 2020).

Past studies have employed different operationalizations of mindfulness. However, most conceptualizations distinguish between two central components of mindfulness: awareness and acceptance (Bishop et al., 2004; Sauer et al., 2013). Nonetheless, Brown et al. (2007) argue that clear awareness of internal and external present-moment experiences is the first and foremost aspect of mindfulness. The authors define awareness as being aware of all physical senses as well as emotional and mental activities. In the context of organizational functioning, being aware seems especially valuable as it is a vital prerequisite for staying attentive and present while being engaged in a (work) task (Good et al., 2016). Accordingly, we want to follow most studies on mindfulness at work that measured mindfulness unidimensionally in the form of awareness – particularly when assessing state mindfulness in the workplace (Hülsheger et al., 2013, 2014; Haun et al., 2018).

In general, there is good evidence for mindfulness to play an essential role in performance. Mesmer-Magnus et al. (2017) reported meta-analytical evidence that employees high in trait mindfulness may work harder and perform better than employees low in mindfulness. However, understanding the state mindfulness’ role for organizational outcomes is insufficient (Forjan et al., 2020). Studies on naturally occurring short-term fluctuations of workplace mindfulness and how they relate directly to short-term performance variability are limited. To our knowledge, only Forjan et al. (2020) tested the intraindividual link at the day-level and found that on days when employees experienced heightened mindful awareness, they also reported stronger daily task performance. Similarly, Haun et al. (2020) reported a positive within-person correlation of awareness and goal attainment at work. We want to examine this relationship further and propose the following hypothesis based on these recent study results:

In this study, we examine state mindfulness and state vigor as separate predictors of daily fluctuations in job performance. However, our main hypothesis suggests an interactive effect between these personal resources, beyond their individual impacts. Specifically, we propose the possibility of a negative interaction, whereby low energetic states can be compensated by high levels of mindfulness. This assumption is grounded in the shared underlying mechanisms through which both influence performance.

The positive effect of vigor on performance may be easily explainable by its energetic function: feeling vigorous, employees can approach their work tasks with more energy (Owens et al., 2016). Energy states indicate how much effort an employee is willing and ready to contribute (Schiuma et al., 2007). Energy is also involved in other motivational processes such as directing one’s effort to a work task and regulating the persistence in carrying it out (Owens et al., 2016). All in all, the capacity for action is increased in vigorous individuals so that work goals are achieved more easily (Owens et al., 2016). However, the linking mechanism is more complex: vigor is a positive experience per se as it is one aspect of positive affect (Shirom, 2011). Thus, notions about the association of positive affect with task performance are applicable.

In more detail, vigor may facilitate task performance through improved self-regulation and different mechanisms on cognitive, behavioral, and emotional levels: concerning self-regulation, some researchers consider energy as the accessibility of glucose in the blood, which determines the momentary capacity to self-regulate behavior (e.g., Gailliot et al., 2007). Following the model of Beal et al. (2005), self-regulation is the crucial factor for dynamic performance. Aside from self-regulation, Shirom (2003) argues that vigor generates a particular thought-action repertoire that expands activity and broadens the range of options. Furthermore, the broaden-and-build theory (Fredrickson, 2001) states that positive affects broaden the range of attention and cognition. Consequently, employees in a positive mood tend to see the big picture, take a holistic perspective, and show more approach tendencies (Diener et al., 2020). They also tend to have expanded cognitive repertoires, which leads to more problem-solving confidence (Forjan et al., 2020), efficient decision-making (Chuang, 2007), and increased creativity (Baas et al., 2008) – all potential facilitators of task performance.

Referring to mindfulness theories (e.g., Glomb et al., 2011; Good et al., 2016), we propose that mindfulness will trigger highly parallel mechanisms positively impacting job performance. Self-regulation of thoughts, emotions, and behavior is considered the central outcome of mindfulness with beneficial effects on performance (Glomb et al., 2011). This assumption is underlined by findings that electrophysiological features of mindfulness are associated with the self-regulation of attention (Verdonk et al., 2020) and the importance of self-regulation of attention to adequately concentrate on a task despite off-task concerns (Beal et al., 2005). Good et al. (2016) also emphasize improvements in stability, control, and efficiency of attention as the linkage between mindfulness and various other improvements in cognitive, emotional, and behavioral domains of functioning. Dane (2011) argues that broad attentional breadth held in the present moment is the key characteristic of mindfulness that influences task performance. In such a broad attentional state, employees are able to focus with due attention to the current task, but without losing their situational awareness (van Gordon et al., 2014). Additionally, mindfulness has been linked to cognitive capacity – especially in terms of improved working memory (Roeser et al., 2013) –, cognitive flexibility (Moore and Malinowski, 2009), and creativity (Baas et al., 2014). Glomb et al. (2011) argue that mindfulness fosters reduced automaticity of mental processes, which creates a mental gap between stimulus and behavioral response. This gives individuals response flexibility, which allows them to consciously choose behavioral responses to attain more adaptive outcomes (Good et al., 2016). In this way, the range and quality of possible reactions increases (Glomb et al., 2011). On a behavioral level, Weinstein et al. (2009) also found that mindful individuals confronted with stressful demands reported more approach than avoidance coping strategies. Furthermore, studies on mindfulness suggest that it leads to more positive and less negative affective reactions and quicker recovery from adverse work events (Glomb et al., 2011). It enables mindful people to avoid automatic, maladaptive emotional reactions and negative affective states by reflecting experiences from a meta-perspective (Malinowski and Lim, 2015). At this point, further beneficial effects of positive affective states may occur.

Considering all this, it becomes salient that mindfulness and vigor share many of the mechanisms in which they influence performance. First, both internal states influence job performance because they improve the capacity to self-regulate. The feeling of vigor indicates that self-regulatory resources are available, whereas mindfulness simplifies the act of self-regulation. This makes it easier for the employee to stay attuned to the current task. Second, vigor and mindfulness are accompanied by similar changes in cognition, behavior, and emotion (Good et al., 2016; Diener et al., 2020). Cognitively, both are associated with flexibility and breadth of mental processes. Behaviorally, both promote approach rather than avoidance strategies. Emotionally, both are either in themselves positive experiences or foster them.

According to the substitution hypothesis of conservation of resources theory (Hobfoll et al., 1990), personal resources are substitutable for each other. Both high state mindfulness and high state vigor can create a mindset that enhances employees’ performance. When this mindset is activated by one of these resources, improvements in performance may not arise from the other resource. However, if an employee is lacking either mindfulness or vigor, it is hypothesized that the other resource can compensate for the deficit and mitigate the decline in performance. Therefore, we assume a compensation effect:

The criteria for study participation included regular employment with a minimum of 30 h per week. As this study was part of a major research project, another inclusion criterion was responsibility for at least one child aged 0–12 years living in the same household. This criterion was unrelated to our specific research question. We employed convenience sampling methods: Potential participants were contacted by social networks, such as XING and Facebook, and via personal contacts. To increase the motivation for participation, we promised to provide general feedback regarding the study results and an invitation to a workshop concerning the reconciliation of work and family duties. Furthermore, the participants received information about data protection regulations and the voluntariness of participation. They were asked to provide a formal informed consent to participate.

In total, 192 participants started the diary surveys resulting in 926 after-work surveys during the 5 days (34 after-work surveys missed). We further analyzed whether the actual measurement points corresponded with the predetermined survey schedule or not (e.g., a participant completing his after-work survey at night or next morning). In the latter case, we set the values of the respective study variables of that measurement point to “missing value.” In total, the dataset contained 848 after-work surveys of 189 participants completed at the correct time. In total, 52% of the participants were females. The mean age was 40 years (SD = 7.5), and 53% had a university degree. The mean working time indicated by the participants was 32 h per week (SD = 12). At the day-level, participants indicated on average 7.1 h.

In the daily after-work questionnaire, we assessed task performance, mindfulness state at work, and vigor. All items were assessed on a 5-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree).

To examine whether the day-level measures of mindfulness, vigor and task performance were empirically distinct, we conducted Multilevel Confirmatory Factor Analysis (MCFA) via MPlus 8.4 (Muthén and Muthén, 1998–2017). The 3-factor day-level solution displayed acceptable fit to the data, χ² = 247.99, df = 84, p < 0.001, CFI = 0.95, TLI = 0.93, RMSEA = 0.04, SRMR = 0.04 (within level) and 0.13 (between level).

From a methodological point of view, our study has several limitations. First, all our variables were assessed with self-report measures and at the same measurement occasions (end of the working day). Therefore, common method bias may limit the validity of our results (Podsakoff et al., 2003). However, vigor and mindfulness are internal states and, as such, inherently subjective. Thus, they can hardly be assessed with other than self-report measures because of observability issues. To lower the concerns of common method bias that our findings are due to inter-individual traits, we centered the day-level predictor variables vigor and mindfulness at the individual mean (person-mean centering) so that all person-level variance was removed (Sonnentag and Niessen, 2008). Furthermore, the mean correlations of about 0.3 and the interaction effect give us confidence that our findings are not due to common method bias (Siemsen et al., 2010). For job performance, however, other measures exist (e.g., supervisor or co-worker ratings of performance, objective indicators), which are significantly less prone to social desirability in comparison to self-reports (Carpenter et al., 2014). However, in this study, we compare the daily performance rating of a person with their own performance ratings on other days so that self-presentational biases should be less of an issue (Beal et al., 2005). Moreover, employees usually know their daily tasks and objectives best in order to assess how far they have reached their goals, especially in such a short timeframe as 1 day (Kampf et al., 2021). Nevertheless, future research should use diverse measuring sources and separate and multiply measurement points throughout the working day (e.g., vigor and mindfulness in the morning and at noon).

Second, due to our correlational study design, causal conclusions cannot be drawn. Therefore, it remains unclear if vigor and mindfulness indeed increase job performance, as the relationship may also be reciprocal or reversed. For example, employees who observe significant achievements may experience increased vigor, while mindfulness may heighten awareness of minor tasks completed. Future studies could manipulate mindfulness (e.g., by mindfulness interventions before the workday) to investigate if the same results occur.

There is growing support for the notion that the comprehension of short-timeframe within-person performance variability has important implications regarding personnel development interventions (Dalal et al., 2020). In particular, it could help prevent short-term minimum performance called troughs (Dalal et al., 2014; Good et al., 2016). The results linking variability in both vigor and mindfulness to fluctuations in job performance offer potential avenues for addressing this issue. Both state mindfulness and state vigor independently impact performance, suggesting two approaches to enhance task performance. First, interventions could target the reduction of vigorless days. As day-level recovery is an important predictor of day-level work engagement (Sonnentag et al., 2010), recovery seems to be a fruitful approach for that. Therefore, job design should provide sufficient job resources to counterbalance job demands, reduce strain, and facilitate recovery (Demerouti et al., 2009). While this may raise mean levels of vigor and the frequency of invigorated days, there will always be less energetic days. In this case, mindfulness could function as a compensator. Again, there are possibilities to design jobs for mindful work (see Lawrie et al., 2018) and mindfulness trainings to raise trait mindfulness (Vonderlin et al., 2020). However, in light of our results, promoting the use of mindfulness tools when needed, such as mindfulness meditation practices (Hülsheger et al., 2013) can avert a working day marked by troughs. Just-in-time adaptive interventions could be a means for that (Nahum-Shani et al., 2018).