Psychological recovery: Progressive muscle relaxation (PMR), anxiety, and sleep in dancers

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Highlights

  • Audio PMR in the home environment appears to enhance sleep in dancers with high trait social evaluation anxiety and poor sleep onset latency.

  • Dancers had relatively low sleep hours and high efficiency, similar to published dance and athlete samples.

  • There were no recorded effects of caffeine or screen time on dancers’ sleep onset latency in this study.

Abstract

The current study was designed to test the efficacy of progressive muscle relaxation (PMR) in improving the sleep onset latency (SOL) of full time dancers. A pre and post intervention study design examined sleep duration and efficiency, and change in SOL as a function of trait anxiety using PMR for the intervention. Twelve female dancers aged 18–23 years were recruited from the Queensland University of Technology dance programme. Trait anxiety was differentiated into social evaluation, physical danger, and ambiguous dimensions using the Endler Multidimensional Anxiety Scale-Trait (EMAS-T) scales. Sleep parameters were monitored using wristwatch actigraphy over a 14 day period with a PMR intervention in Week 2. Sleep duration and efficiency were compared to published data, and improvements in SOL were examined for those with poorer baseline SOL and higher trait anxiety. Sleep duration and efficiency in this sample did not significantly differ to that of previously published data from athlete and dance samples. Participants with high trait social evaluation anxiety showed a statistically significant decrease in SOL from Week 1 to Week 2 (Z = −2.02, p = .04), with a large effect size (r = .90) following PMR training. Sleep needs of full time dancers differ to those of the general population. PMR is indicated as an effective strategy for improving SOL in higher trait social evaluation anxiety elite performers. Replication with a large randomised controlled trial and an athlete sample is needed.

Introduction

This study was conceptualised in response to the assistance given to athletes by the sports science and psychology staff at the Australian Olympic team's recovery centre during the London 2012 Olympic Games. Sleep was viewed as vital for athletes’ recovery at the games, and progressive muscle relaxation (PMR) was employed as a relaxation strategy to offset the psychological (cognitive) and physical (somatic) stressors experienced. There is evidence for the use of PMR in the general population as an effective treatment for sleep issues, but little evidence exists to support the use of PMR for performers. For the purpose of this study, “elite” refers to highly skilled, and “performers” refers to those who perform or execute a physical skill. The present study was a preliminary pilot evaluation of PMR in full time dancers with the view to replication with an athlete sample and a larger randomised controlled trial in the future.

Recovery is defined as the re-establishment of psychological and physiological resources to allow for future use (Kellman & Kallus, 1999). Different performance contexts involve different physical and mental stressors in training and performance, and individuals differ in their abilities to cope with stressors. Responsible for the secretion of the stress hormone cortisol, the hypothalamic–pituitary–adrenal (HPA) axis is primarily activated when the body responds to stress (Miller & O’Callaghan, 2002). Socio-evaluative threat (the threat of negative evaluation from others) during training and performance can activate the HPA axis (Suay et al., 1999). During stress, elite performers experience a deviation from the homeostasis state, requiring restoration during recovery for training and performance standards to be maintained (Beckmann & Kellmann, 2004).

Athletes, coaches, and trainers identify sleep as an important aspect of the recovery process and crucial for optimal performance (Postolache et al., 2005, Samuels, 2008). Physically, sleep is critical for protein synthesis, growth hormone release, and for the facilitation of glucose metabolism (Davenne, 2009, Spiegel et al., 2009). Sleep also has been identified as the most important factor in performance on cognitive tasks (Pilcher and Huffcutt, 1996, Rosekind, 2005). Research on the effects of sleep loss on athletic performance has found that mood, psychomotor, and cognitive function decline more rapidly than physical capabilities (Davenne, 2009, Mougin et al., 1991, Souissi et al., 2003). The benefits of sleep extension have demonstrated measurably improved athletic performance (Mah, Mah, Kezirian, & Dement, 2011). Therefore, sleep appears to have a vital role in recovery, and the sleep needs of elite performers may differ from other populations (Davenne, 2009).

Theorists have suggested that sleep quality and patterns differ for athletes compared to nonathletic populations (Davenne, 2009, Leger et al., 2005, Savis, 1994). Wristwatch actigraphy has been used to measure the sleep of elite athletes (Leeder, Glaister, Pizzoferro, Dawson, & Pedlar, 2012). Actigraphy is an objective measure of sleep involving a device worn on the wrist of the user to record the number and amplitude of movements. Used in conjunction with a sleep diary, actigraphy provides a validated alternative to laboratory-based polysomnography (PSG) recording of some sleep parameters (Kushida et al., 2001, Vallieres and Morin, 2003). Significant differences have been reported between athletes and age- and sex-matched controls across time in bed, sleep onset latency (SOL), time awake, sleep efficiency, actual sleep, moving minutes, and moving time (Leeder et al., 2012). Greater individual variance was found within each variable for the athletes, suggested to be due to differential physiological and psychological stress (Leeder et al., 2012). A study of elite dancers recorded similar baseline data to athletes during a normal training phase (Fietze et al., 2009, Leeder et al., 2012).

Psychological factors such as trait anxiety have been found to affect sleep quantity and quality (Du et al., 2009, Kajimura et al., 1998, Savis, 1994). In several studies of both clinical and general populations, individuals with high trait anxiety have demonstrated chronically poor SOL and a higher number of awakenings during the night (Du et al., 2009, Kajimura et al., 1998, Viens et al., 2003). Pre-performance sleep problems are widely reported by elite athletes and in elite dance populations (Erlacher et al., 2009, Fietze et al., 2009). Recent research demonstrated a strong negative association between pre-sleep state anxiety and self-reported sleep quality of athletes (Romyn, Robey, Dimmock, Halson, & Peeling, 2015). In a review of sleep and sport, it was concluded that more sophisticated research was required because current interventions have been based largely on clinical experience and evidence derived from fields not relevant to athletes (Postolache et al., 2005). Sleep medication is not ideal for athletes due to possible effects on physical and cognitive performance during subsequent training and performance (Leger et al., 2005). For the management of insomnia and sleep disruption in athletes, relaxation may greatly help during regular training periods and before competitions (Leger et al., 2005).

PMR has been one of the most widely investigated of all relaxation strategies and is recognised by the American Psychological Association as an empirically supported treatment for insomnia (de Niet et al., 2009, McCallie et al., 2006, Morin et al., 1999). The mechanisms of its efficacy are suggested to be based upon the known connection between stress and sleep issues (Van Reeth et al., 2000). The conscious directed initiation of the homeostasis-restoring parasympathetic nervous system (PNS) branch of the autonomic nervous system down-regulates the over-active HPA axis, supported by evidence of a post PMR reduction in salivary cortisol and increased heart rate variability (Dolbier & Rush, 2012).

PMR is the use of scripts (in-person, audio, or video) involving tensing (4–7 s) and then relaxing (20–45 s) different muscle groups throughout the body (McCallie et al., 2006, Mezo et al., 2011, Taylor and Roane, 2010). PMR is undertaken seated on a chair with the feet on the floor next to each other, knees in a 90° angle, arms resting on upper legs; or, laying down with arms next to body and support under knees or knees bent; takes between 8 and 30 minutes; and may or may not involve daytime practice as well as use before bedtime (Taylor & Roane, 2010). The feelings of relaxation and the contrast between feelings of tension and relaxation raise individuals’ awareness and recognition of tension, allowing conscious relaxation.

In summary, evidence has indicated that elite performers have different sleep requirements than the general population. Sleep is an important recovery strategy after physical and psychological stress for elite performers to return to homeostasis (Halson, 2008). Trait anxiety has been found to influence poor sleep quality, in particular SOL, in general and clinical populations with sleep issues. The efficacy of PMR in enhancing the sleep of elite performers has not been established. The current study was designed to test the efficacy of PMR in improving the SOL of full time dancers. It was hypothesised that full time dancers would record shorter sleep durations with less efficient sleep than general populations in line with published data; and that a PMR intervention would improve the SOL of full time dancers with poor SOL and high trait anxiety.

Section snippets

Method

Participants were recruited from the Queensland University of Technology (QUT) Dance programme (n = 12; mean age 20.09 years, SD = 1.45; 84% identifying as Caucasian, 8% South African, and 8% Asian). Participation was voluntary. Inclusion criteria for the study comprised age of at least 18 years of age, female gender, and full-time participation at an elite performance level. All participants were in a stable training phase (daily average = 3 h 39 m, SD = 33 m) during the study. A single gender sample was

Results

There were no missing data and all data were inspected to ensure that scores were within scale response limits. Normality was evaluated by examining skewness and kurtosis values and data were screened for potential outliers. All variables met the assumptions of normality except sleep onset was positively skewed. An inverse transformation to normalise the distribution was performed (Tabachnick & Fidell, 2007). The transformation failed to improve the skewness therefore analyses of the

Discussion

The aim of the current study was to test the efficacy of PMR as a natural sleep aide and recovery strategy for full time dancers to assist applied performance psychologists in preparing performers mentally with empirically sound techniques to ensure quality recovery and performance/s. PMR is widely used by athletes, although the efficacy of its application in this context has not been evaluated.

Hypothesis 1, that elite performers would record shorter sleep durations with less efficient sleep

Conclusion

General findings of physical, cognitive, and mood effects due to sleep loss are widely reported in clinical, general, and performance samples (Fietze et al., 2009, Postolache et al., 2005, Savis, 1994). Despite indicators of quality sleep, athletes may require more sleep than they achieve on average (Davenne, 2009, Mah et al., 2011). Sub-optimal sleep duration can be further exacerbated for individuals with sleep problems, affecting recovery from training and performance stressors. The use of

Acknowledgements

The Australian Institute of Sport supplied the actigraphy devices and the computers and software for data processing and analysis. Acknowledgement to Laura Juliff (Australian Institute of Sport) and Assoc Prof Gene Moyle (Queensland University of Technology, Dance). There has been no financial assistance with this project.

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