Potential Benefits of Daytime Naps on Consecutive Days for Motor Adaptation Learning.

Daytime napping offers benefits for motor memory learning and is used as a habitual countermeasure to improve daytime functioning. A single nap has been shown to ameliorate motor memory learning, although the effect of consecutive napping on motor memory consolidation remains unclear. This study aimed to explore the effect of daytime napping over multiple days on motor memory learning. Twenty university students were divided into a napping group and no-nap (awake) group. The napping group performed motor adaption tasks before and after napping for three consecutive days, whereas the no-nap group performed the task on a similar time schedule as the napping group. A subsequent retest was conducted one week after the end of the intervention. Significant differences were observed only for speed at 30 degrees to complete the retention task, which was significantly faster in the napping group than in the awake group. No significant consolidation effects over the three consecutive nap intervention periods were confirmed. Due to the limitations of the different experimental environments of the napping and the control group, the current results warrant further investigation to assess whether consecutive napping may benefit motor memory learning, which is specific to speed.

Effect of napping on a bean bag chair on sleep stage, muscle activity, and heart rate variability.

Background: Although ample evidence has demonstrated that daytime napping is beneficial for health and cognitive performance, bedding for napping has not yet been scientifically investigated. Objectives: To explore the effect of a bean bag chair on daytime napping and physiological parameters related to sleep. Methods: Fourteen healthy participants were enrolled within the context of a randomized, single-blind, crossover study to evaluate the effects of a bean bag chair in comparison with those of a urethane chair manufactured to have a similar shape. Electroencephalogram, electromyogram, and heart rate variability were recorded and compared between wakefulness and napping. Results: Electroencephalogram analyses revealed no significant differences in sleep architecture or frequency components; however, a significant decrease was found in electromyogram recordings in the trapezius muscle, which represents the neck region (p = 0.019). Additionally, a significant main effect of bedding in the low-frequency/high-frequency ratio (F[1,20] = 4.314, p = 0.037) was revealed. Conclusions: These results suggest that napping in a bean bag chair may provide a comfortable napping environment involving muscle relaxation and proper regulation of the autonomic nervous function.

Effects of Sleep Restriction on Self-Reported Putting Performance in Golf.

In the present study, we aimed to explore the effects of sleep restriction (SR) on self-reported golf putting skills. Eleven collegiate golfers participated in a self-reported, counterbalanced experimental study under two conditions: (a) a SR condition in which sleep on the night prior to putting was restricted to 4-5 hours, and (b) a habitual normal sleep (NS) condition on the night before the putting test. Following each sleep condition, participants engaged in ten consecutive putting tests at 7 am, 11 am, and 3 pm. Participants reported their subjective sleepiness before each time frame, and their chronotype, defined as their individual circadian preference, was scored based on a morningness-eveningness questionnaire (MEQ). Participants restricted sleep to an average period of 267.6 minutes/night (SD = 51.2) in the SR condition and 426.2 (SD =38.0) minutes/night in the NS condition. A two-way analysis of variance revealed a significant main effect of the sleep condition on the lateral displacement of putts from the target (lateral misalignment) (p = 0.002). In addition, there was a significant main effect of time on distance from the target (distance misalignment) (p = 0.017), indicating less accuracy of putting in the SR condition. In the SR condition, the MEQ score was positively correlated with distance misalignment at 3 pm (ρ = 0.650, p = 0.030), suggesting that morningness types are susceptible to the effects of SR on putting performance. Our findings suggest that golfers should obtain sufficient sleep to optimize putting performance.

Exploring the Effect of Long Naps on Handball Performance and Heart Rate Variability.

This study explored the effect of long naps on handball-related performance and assessed the role of the cardiac autonomic nervous system in this process. Eleven male collegiate handball players performed a repeated sequential trial consisting of a 20-m consecutive turnaround run, 10-m run with a load, and shooting the ball into a target. Participants were allocated randomly and sequentially to have a short (20 minutes) nap, long (60 minutes) nap, or no nap. The Pittsburgh Sleep Quality Index was used to assess regular sleep quality. Subjective sleepiness before and after napping was measured using the Karolinska Sleepiness Scale. Heart rate variability was recorded to assess cardiac autonomic nervous function during napping. The Pittsburgh Sleep Quality Index score was correlated with shot accuracy only after long naps (ρ=0.636, r=0.048). A negative correlation was observed between the root mean square of successive differences and average load run time (ρ=-0.929, p<0.001). Long napping was associated with a significant benefit on performance in athletes with poor sleep quality, implying a role of the autonomic nervous system in this regard. Our findings indicate the effect of sleep quality on the endurance and resistance of handball players.

Simultaneous Knee Extensor Muscle Action Induces an Increase in Voluntary Force Generation of Plantar Flexor Muscles.

Suzuki, T, Shioda, K, Kinugasa, R, and Fukashiro, S. Simultaneous knee extensor muscle action induces an increase in voluntary force generation of plantar flexor muscles. J Strength Cond Res 31(2): 365-371, 2017-Maximum activation of the plantar flexor muscles is required for various sporting activities that involve simultaneous plantar flexion and knee extension. During a multi-joint movement, activation of the plantar flexor muscles is affected by the activity of the knee extensor muscles. We hypothesized that coactivation of the plantar flexor muscles and knee extensor muscles would result in a higher plantar flexion torque. To test this hypothesis, 8 male volunteers performed maximum voluntary isometric action of the plantar flexor muscles with and without isometric action of the knee extensor muscles. Surface electromyographic data were collected from 8 muscles of the right lower limb. Voluntary activation of the triceps surae muscles, evaluated using the interpolated twitch technique, significantly increased by 6.4 percentage points with intentional knee extensor action (p = 0.0491). This finding is in line with a significant increase in the average rectified value of the electromyographic activity of the vastus lateralis, fibularis longus, and soleus muscles (p = 0.013, 0.010, and 0.045, respectively). The resultant plantar flexion torque also significantly increased by 11.5% of the predetermined maximum (p = 0.031). These results suggest that higher plantar flexor activation coupled with knee extensor activation facilitates force generation during a multi-joint task.

Effect of 2 days of intensive resistance training on appetite-related hormone and anabolic hormone responses.

This study was designed to determine endocrine responses during 2 days of strenuous resistance training. Ten healthy men performed resistance training twice a day for two successive days to induce acute fatigue (excessive physical stress). The resistance training consisted of four exercises for the lower body in the morning and seven exercises for the upper body in the afternoon. Maximal isometric and isokinetic strengths were measured from day 1 (before the training period) to day 3 (after the training period). Fasting blood samples were taken on days 1-3. Maximal isometric and isokinetic strengths significantly decreased with two successive days of training (P<0·05), with significant increases in serum creatine phosphokinase and myoglobin concentrations (P<0·05). Significant reductions in the fasting concentrations of serum insulin-like growth factor-1, free testosterone, insulin and high-molecular-weight adiponectin were observed on day 3 (P<0·05), whereas there were no changes in the serum cortisol concentration or the free testosterone/cortisol ratio. Plasma active ghrelin and serum leptin concentrations decreased by -20·7 ± 2·8% and -29·6 ± 4·1%, respectively (P<0·05). Two days strenuous resistance training significantly affects the profiles of anabolic hormone and endocrine regulators of appetite and energy balance, such as ghrelin and leptin. The present findings suggest that decreased ghrelin and leptin concentrations might reflect excessive physical stress and may be early signs of accumulated fatigue.

Exercise effects on sleep physiology.

This mini-review focuses on the effects of exercise on sleep. In its early days, sleep research largely focused on central nervous system (CNS) physiology using standardized tabulations of several sleep-specific landmark electroencephalogram (EEG) waveforms. Though coarse, this method has enabled the observation and inspection of numerous uninterrupted sleep phenomena. The research on the effects of exercise on sleep began, in the 1960s, with a focus primarily on sleep related EEG changes (CNS sleep). Those early studies found only small effects of exercise on sleep. However, more recent sleep research has explored not only CNS functioning, but somatic physiology as well. Sleep should be affected by daytime exercise, as physical activity alters endocrine, autonomic nervous system (ANS), and somatic functions. Since endocrinological, metabolic, and autonomic changes can be measured during sleep, it should be possible to assess exercise effects on somatic physiology in addition to CNS sleep quality, evaluated by standard polysomnographic (PSG) techniques. Additional measures of somatic physiology have provided enough evidences to conclude that the auto-regulatory, global regulation of sleep is not the exclusive domain of the CNS, but it is heavily influenced by inputs from the rest of the body.