Reciprocal Associations Between Sleep, Mental Strain, and Training Load in Junior Endurance Athletes and the Role of Poor Subjective Sleep Quality

Abstract

The importance of adequate sleep for athletic functioning is well established. Still, the literature shows that many athletes report sleep of suboptimal quality or quantity. To date, no research has investigated how bidirectional variations in mental and physiological states influence sleep patterns. The present study, therefore, investigates reciprocal associations between sleep, mental strain, and training load by utilizing a prospective, observational design. In all, 56 junior endurance athletes were followed over 61 consecutive days. Unobtrusive, objective measurements of sleep with novel radar technology were obtained, and subjective daily reports of mental strain and training load were collected. The role of subjective sleep quality was investigated to identify whether the reciprocal associations between sleep, mental strain, and training load depended on being a good versus poor sleeper. Multilevel modeling with Bayesian estimation was used to investigate the relationships. The results show that increases in mental strain are associated with decreased total sleep time (TST, 95% CI = −0.12 to −0.03), light sleep (95% CI = −0.08 to −0.00), and sleep efficiency (95% CI = −0.95 to −0.09). Further, both mental strain and training load are associated with subsequent deceased rapid eye movement (REM, respectively, 95% CI = −0.05 to −0.00 and 95% CI = −0.06 to −0.00) sleep. Increases in TST, light, deep, and REM sleep are all associated with subsequent decreased training load (respectively, 95% CI = −0.09 to −0.03; 95% CI = −0.10 to −0.01; 95% CI = −0.22 to −0.02; 95% CI = −0.18 to −0.03). Finally, among poor sleepers, increases in sleep onset latency are associated with increases in subsequent mental strain (95% CI = 0.09–0.46), and increases in deep sleep are associated with decreases in subsequent training load (95% CI = −67.65 to 11.43). These results offer novel insight into the bidirectional associations between sleep, mental strain, and training load in athletes and demonstrate the detrimental effects of mental strain on sleep, likely caused by mental activation incompatible with sleep. An increased need for recovery, suggested by increased TST and time in different sleep stages, is associated with subsequent self-regulatory reduction of training loads by the athletes. In poor sleepers, increases in deep sleep may suggest an elevated need for physiological recovery.

“When I Sleep Poorly, It Impacts Everything”: An Exploratory Qualitative Investigation of Stress and Sleep in Junior Endurance Athletes

“…We chose to implement qualitative method in this study in order to obtain detailed insight into athletes' own perceptions of the studied variables, stress and sleep, which are currently not available in the literature on junior athletes. Furthermore, as the current qualitative study was part of a larger quantitative research project (Hrozanova et al, 2020 ), we supported the qualitative material with data from relevant questionnaires.…”

“…In this study, we collected daily measures of objective sleep, training load and mental strain, in addition to a single measure of subjective sleep quality to identify good and poor sleepers in the sample. Although unreported in Hrozanova et al ( 2020 ), the study also obtained a measure of sleep reactivity from all participating athletes. The current qualitative study took place at the end of the quantitative data collection.…”

“…The quantitative study by Hrozanova et al ( 2020 ) spanned 61 consecutive days, and included 56 junior endurance athletes from three high schools specialized for elite sports in Norway. In this study, we collected daily measures of objective sleep, training load and mental strain, in addition to a single measure of subjective sleep quality to identify good and poor sleepers in the sample.…”

“…The ability to manage the stressful aspects of athletic careers, and the ability to adequately recover on a continuous basis (Kellmann, 2010 ), i.e., the concepts of stress and sleep, are central requirements for optimal athletic functioning. Research in athletic populations has previously shown that affective and cognitive aspects of stress lead to disrupted sleep (Lastella et al, 2014 ; Juliff et al, 2015 ; Hrozanova et al, 2020 ). However, a thorough understanding of the associations between the stress and sleep is lacking.…”

“…Research has begun to provide evidence of such bidirectional relationships also in athletes. In athletes who were poor sleepers, increases in sleep onset latency were associated with higher subsequent mental strain (Hrozanova et al, 2020 ). Increased sleep onset latencies may have been caused by preservative cognitions at bedtime (Wuyts et al, 2012 ), which may have in turn contributed to increases in mental strain (Galambos et al, 2009 ), possibly leading to further sleep disturbance (Kalmbach et al, 2018a ).…”