Continuous theta burst stimulation improves sleep quality and thereby enhances athletic performance in athletes with sleep disorders: A randomized controlled trial

Abstract

Purpose

Sleep disorders (SD) are prevalent among athletes during training practice, which adversely affects both their physical health and athletic performance. This study investigates the effects of continuous theta burst stimulation (cTBS) on athletes with SD.

Methods

Twenty athletes with SD were recruited and randomly assigned to either the cTBS group or the sham-cTBS group. Participants in both groups received a 48 s cTBS once daily before bedtime for five consecutive days. Sleep quality, athletic performance, reaction speed, and daytime functioning were assessed in athletes with SD both before and after the cTBS.

Results

The statistical significance level was set at α = 0.05 for all analyses. Compared to pre-cTBS, the cTBS group demonstrated significant reductions in sleep onset latency (SOL) (P < 0.001), time awake (TA) (P < 0.001), and PSQI scores (P < 0.001) following cTBS. Total sleep time showed a significant increase (P < 0.001), while subjective physical fatigue (P < 0.001) and mental fatigue (P < 0.01) were significantly decreased. Additionally, a significant improvement was observed in agility test completion time (P < 0.01). In contrast, no significant differences were observed between groups in standing long jump performance, reaction speed, daytime sleepiness scores, or positive and negative affect scores.

Conclusion

A five-day course of cTBS significantly improved subjective sleep quality, increased total sleep time, and reduced SOL and TA in athletes with SD. Additionally, it enhanced agility and alleviated subjective mental and physical fatigue. There was also evidence suggesting potential improvements in reaction speed and emotional experience.

Highlights

• •cTBS can serve as a novel transcranial magnetic stimulation (TMS) protocol to improve sleep disorders in athletes.
• •cTBS to the right DLPFC improves sleep quality in athletes with sleep disorders.
• •Following cTBS intervention, athletic performance and daytime functioning in athletes with sleep disorders also improved.

1. Introduction

Sleep constitutes one of the most fundamental biological processes in humans, during which tissues and organs engage in critical restorative functions to establish physiological preparedness for subsequent diurnal activities.¹ Sleep is likewise recognized as a critical recovery modality for athletes during both competitive engagements and training cycles.² Athletes exhibit more pronounced sleep disturbances due to factors such as high-intensity training regimens, scheduling demands of training cycles, and psychological stressors.3, 4, 5 In 2019, the International Olympic Committee (IOC) formally recognized sleep disorders (SD) as a distinct category of mental health impairment among elite athletes.⁶ Studies have shown that between 50 % and 78 % of elite athletes have experienced varying degrees of SD, with 22 %–26 % reporting severe SD.⁷ Furthermore, SD in athletes has been documented to negatively impact anaerobic power,⁸ reaction speed,⁹ agility¹⁰ and fine motor skill performance.¹¹

Transcranial magnetic stimulation (TMS) is a non-invasive, painless neurostimulation and neuromodulation technique. Theta burst stimulation (TBS), a specialized form of repetitive TMS (rTMS), has gained increasing attention due to its ability to achieve therapeutic effects with shorter stimulation durations, fewer pulses, and lower stimulation intensities compared to conventional rTMS.¹² As a result, TBS has been gradually adopted in clinical diagnosis and rehabilitation across fields such as neurology, rehabilitation medicine, and psychiatry, particularly for the rehabilitation of neurological disorders following stroke.¹³ Currently, the two most common TBS protocols are continuous TBS (cTBS) and intermittent TBS (iTBS). It is widely accepted that cTBS can inhibit cortical excitability and reduce motor-evoked potential amplitudes, while iTBS can enhance cortical excitability and facilitate the generation of motor-evoked potentials.¹⁴ Moreover, patients with comorbid SD frequently exhibit characteristics of cortical hyperexcitability,¹⁵ Conversely, cTBS functions to enhance the secretion of inhibitory neurotransmitters within the brain,¹⁶ thereby suppressing cortical excitability. These findings suggest that cTBS holds potential value in modulating cortical excitability within the central nervous system of athletes with SD, thereby improving sleep quality. This study aims to investigate the effects of cTBS on sleep quality in athletes with SD, furthermore, this study investigated alterations in athletic performance and subjective perceptions among athletes following cTBS, providing a scientific approach to reducing the prevalence of SD among athletes. Based on the above, the following hypotheses are proposed:

Hypothesis 1

cTBS will have a significant effect on sleep quality in SD athletes;

Hypothesis 2

cTBS will significantly influence agility and standing long jump performance in SD athletes;

Hypothesis 3

cTBS will induce significant changes in subjective perceptions in SD athletes.

2. Materials and methods

2.1. Participants

The inclusion criteria for participants were as follows: 1) Male athletes certified at National Level 2 or above, engaging in high-intensity training at least three times per week; 2) A Pittsburgh Sleep Quality Index (PSQI) > 7,¹⁷ SD lasting more than one month; 3) Age between 18 and 30 years; 4) Right-handed, no metal implants in the body; 5) During the experimental period, participants were required to abstain from the consumption of alcohol, nicotine, other medications, or supplements, and to avoid caffeine intake for 12 h prior to the commencement of the study; 6) Additionally, both the Hamilton Anxiety Scale (HAMA)¹⁸ and Hamilton Depression Scale (HAMD)¹⁹ scores were required to be < 7, so as to exclude sleep disturbances caused by severe emotional disorders. A total of 20 athletes diagnosed with sleep disorders (including participants from sprinting, boxing, ice hockey, and short-track speed skating) were ultimately recruited for this study. The baseline characteristics of the subjects are presented in Table 1, and no significant differences were observed in any of the measured variables between the two athlete groups. All participants provided informed consent after being informed of the testing procedures and potential risks. Ethical approval was provided by the Beijing Sport University Ethics Committee (2023277H), and all procedures conformed to the Declaration of Helsinki.

Table 1.

Basic information of participants (n = 20).

	cTBS group (n = 10)	Sham-cTBS group (n = 10)	P
Age (y)	20.85 ± 2.25	20.44 ± 1.74	0.654
Height (cm)	179.30 ± 4.72	179.60 ± 4.40	0.885
Weight (kg)	73.80 ± 4.02	71.43 ± 1.52	0.108
BMI	22.97 ± 1.14	22.17 ± 0.90	0.064
Training history (y)	5.90 ± 1.52	5.70 ± 1.34	0.830
Sessions/Week	4.90 ± 0.99	5.00 ± 1.05	0.759
PSQI	13.00 ± 3.16	12.00 ± 2.45	0.439
HAMA	5.10 ± 1.20	5.20 ± 1.32	0.861
HAMD	5.00 ± 1.63	4.80 ± 1.62	0.786

PSQI: Pittsburgh Sleep Quality Index; HAMA: Hamilton Anxiety Scale; HAMD Hamilton Depression Scale.

2.2. Experimental design and protocol

A total of 39 active athletes were recruited for this study through poster advertisements distributed within professional sports teams. After screening, 19 participants were excluded for not meeting the inclusion criteria, yielding a final sample of 20 individuals. Using a computer-generated random number sequence, the 20 participants were randomly assigned to either a cTBS group (n = 10) or a sham-cTBS group (n = 10) to ensure unbiased allocation to the groups. No participants dropped out for other reasons during the study; hence, all 20 were included in the final analysis. Throughout the experiment, allocation was concealed from both the participants and the research team. The cTBS were administered by a third-party medical professional, and the researchers remained blinded to the type of stimulation each participant received. All pre- and post-test assessments were conducted by the same investigator.

All assessments in this study were conducted in a controlled sleep laboratory environment. All participants were required to visit the sleep laboratory for a total of 8 nights (Fig. 1). Among these, Night 1 was designated as the habituation and adaptation phase; Nights 2 and 8 served as assessment phases; and Nights 3 to 7 (including Night 3) constituted the cTBS phase. During the familiarization and adaptation session, participants were required to become acquainted with all testing tasks and experimental procedures (Fig. 1) to minimize the potential adverse effects of learning effects and physical discomfort on the formal experiment. The specific activities during the familiarization session included: 1) Introducing participants to the principles and application methods of TMS for SD treatment, and conducting TMS safety screenings for all participants in strict accordance with TMS safety guidelines; 2) Guiding participants to familiarize themselves with the testing procedures of the experiment and the administration of the Epworth Sleepiness Scale (ESS), Flinders Fatigue Scale (FFS), and Positive and Negative Affect Scale (PANAS); 3) Familiarizing participants with the testing methods for the “T" agility test (T-test), standing long jump test, and reaction time test; 4) Collecting basic information from participants, such as height and weight. The testing sequence on the 2nd and 8th nights followed the previously familiarized procedures (Fig. 1). During the cTBS phase (nights 3 to 7 prior to bedtime), both the cTBS group and sham-cTBS group underwent cTBS.

Fig. 1.

Experimental flowchart.

To minimize experimental errors, the following measures were implemented in this study: 1) To avoid the “first-night effect” in sleep monitoring, participants were required to spend one adaptation night in the sleep laboratory prior to the formal experiment. During this night, participants familiarized themselves with the experimental procedures without undergoing any testing. The sleep laboratory was maintained at a temperature of 22–25 °C and a relative humidity of 35–45 % during sleep monitoring. 2) To eliminate the influence of physical activity on sleep, athletic performance tests were conducted during the daytime on the 2nd and 8th visits to the sleep laboratory; 3) To reduce the impact of circadian rhythms, participants were required to undergo sleep testing or cTBS at the same time of day for each session. All tests were completed within a two-week period.

2.3. Methods

2.3.1. Resting motor threshold assessment

To address safety concerns related to TMS and account for individual variability in sensitivity to the magnetic fields generated by TMS, a comprehensive safety screening was conducted for all participants. Following confirmation of eligibility, the minimum stimulation intensity required for each participant was determined prior to the first stimulation session. Participants were first assisted in wearing the TMS positioning cap. The intersection of the naso-occipital and temporoparietal lines on the cap was aligned with the midpoint of the line connecting the nasion and inion. The cap was adjusted to ensure a snug yet comfortable fit. Participants were seated in a chair with back support, with their hands resting palms-up on their knees in a relaxed and natural position. Motor-evoked potentials (MEPs) were recorded using electrode leads during single-pulse TMS. The recording electrode was placed on the belly of the right abductor pollicis brevis (APB) muscle, the reference electrode was positioned on the tendon distal to the muscle, and the ground electrode was placed on the wrist. Based on the functional map of the somatotopic representation in the primary motor cortex(M1), the region corresponding to the thumb was identified on the positioning cap. The left M1 area was stimulated using single-pulse TMS while observing contractions in the right abductor pollicis brevis (APB) muscle.²⁰ The optimal stimulation site was determined as the location that elicited the most consistent motor-evoked potentials (MEPs) in the APB. The stimulation intensity was then gradually reduced to identify the minimum intensity required to elicit MEPs with amplitudes exceeding 50 μV in at least 5 out of 10 consecutive stimuli. This intensity was defined as the participant's resting motor threshold (RMT).^21,22 Throughout the procedure, any adverse reactions reported by participants resulted in immediate cessation of stimulation to ensure their safety.

2.3.2. cTBS intervention

The cTBS protocol in this study was delivered using a YRD CCY-IIIB magnetic stimulator (Yiruide, China) equipped with a superficial figure-of-eight coil. All procedures were conducted in accordance with the safety guidelines for the application of TMS.²³ The stimulation intensity was set at 80 % of the RMT for this study. This intensity was selected because higher stimulation levels are associated with an increased risk of adverse effects, whereas 80 % RMT has been shown to ensure therapeutic efficacy while effectively minimizing the incidence of side effects.^24,25 The specific procedure was as follows: For the cTBS group, the center of the figure-of-eight coil was positioned over the right dorsolateral prefrontal cortex (DLPFC) of participants, and cTBS was administered at 80 %RMT for 48 s. The stimulation parameters were as follows: 3 pulses per burst, intra-burst frequency of 50 Hz, intra-burst duration of 0.06 s, inter-burst frequency of 5 Hz, total stimulation duration of 40 s, and an inter-train interval of 8 s, resulting in a total of 600 pulses delivered over 48 s. The coil was placed tangentially to the scalp, with the handle pointing backward at a 45° angle from the midline.²⁴ Stimulation was performed once daily before bedtime for a total of 5 days. The sham-cTBS protocol was identical to the cTBS in all respects except for the intensity level. The output intensity was reduced to 20 % of the RMT, which is sufficiently low to preclude any physiological effects on the cerebral cortex.²⁶

2.3.3. Sleep quality monitoring

Accelerometers are commonly used to assess nighttime sleep.^27,28 In this study, the GT3X + accelerometer (ActiGraph, USA) was secured on the right hip of participants before bedtime to record overnight sleep data. The recorded sleep data were then processed using the ActiLife software in conjunction with sleep diaries. The method combining the Cole-Kripke algorithm with sleep diaries has been demonstrated to exhibit minimal discrepancies compared to polysomnography (PSG) in assessing the following parameters: sleep onset latency (SOL),²⁹ defined as the period from self-reported bedtime in sleep diaries to algorithm-classified sleep onset; total sleep time (TST),³⁰ calculated from algorithm-detected sleep onset to wake time recorded in sleep diaries; and time awake (TA),³⁰ representing the total duration of algorithm-identified wakefulness after sleep onset. During sleep data processing, the “Sleep” analysis module in ActiLife data analysis software was utilized. Bedtime and wake time from participants' sleep diaries were input, and the Cole-Kripke algorithm was selected to classify sleep/wake status for each minute between bedtime and wake time (i.e., each minute was algorithmically scored as sleep or wake). This process generated parameters including SOL, TST, and TA. The sleep fragmentation index (SFI) was derived from the ActiLife algorithm to quantify nocturnal restlessness, with higher SFI values indicating greater sleep discontinuity and increased frequency of sleep interruptions.^31,32

2.3.4. Athletic performance assessment

2.3.4.1. Agility assessment

The T-test evaluates change-of-direction speed through a series of movements, including linear acceleration, deceleration, lateral shuffle, and backward running (Fig. 2).³³ During testing, the athletes initiated the test from a three-point stance starting position. Upon the examiner's start command, the athlete sprinted forward, shuffled to the left, then to the right, followed by another shuffle to the left, and finally backward running to the starting line to complete the test. During the test, athletes were required to touch each cone with the hand corresponding to the direction of the shuffle (e.g., left hand for a left shuffle). Crossing the feet during lateral shuffling was not permitted, and any violation resulted in test termination. A stopwatch was used to record the time from the start of the movement until the athlete returned to the starting line. Each participant performed the test twice—once starting with a left shuffle and once with a right shuffle—with the final result being the average of the two trials.

Fig. 2.

Schematic diagram of the T-test agility test course.

2.3.4.2. Standing long jump test

Participants stood with their feet naturally apart behind the take-off line, ensuring that their toes did not cross the line. They performed a two-footed jump from a stationary position, and the linear distance from the back edge of the take-off line to the nearest landing point was measured. Each participant performed two attempts, and the average distance was recorded as the final result.

2.3.5. Reaction speed test

Reaction speed was measured using the GMCS-FYS reaction time tester (Xin Dong Hua Teng, China). Participants stood in an upright position and focused their attention. When the tester's light illuminated, participants were required to quickly press the button to turn off the light. Each participant completed three trials, and the average reaction time was recorded. Reaction time serves as an indicator of neural response speed.

2.3.6. Questionnaires

2.3.6.1. Subjective sleep quality

The Pittsburgh Sleep Quality Index (PSQI) is a scale used to assess subjective sleep quality. It comprises seven components (sleep quality score, sleep latency score, sleep duration score, sleep efficiency score, sleep disturbance score, use of sleep medication score, and daytime dysfunction score). A higher total score indicates poorer subjective sleep quality.¹⁷ In this study, the PSQI was employed as a supplementary metric to assess sleep in athletes with SD. During the screening and pre-test phases, participants were instructed to evaluate their sleep patterns over the past month, whereas in the post-test phase, they were required to report sleep characteristics spanning from the initiation of cTBS to the night of post-test assessment.

2.3.6.2. Daytime sleepiness scale

The ESS is primarily used to assess the degree of daytime sleepiness in various daily scenarios.³⁴ This self-report scale consists of 8 items, each scored from 0 to 3, with a total possible score of 24. Higher scores indicate more severe sleepiness. A score of 6–11 suggests mild to moderate sleepiness, while a score greater than 11 indicates excessive sleepiness.

2.3.6.3. Fatigue scale

The FFS is a tool designed to measure fatigue levels in the general population,³⁵ and can also be used to assess daytime fatigue associated with insomnia.³⁶ The scale consists of two dimensions: physical fatigue (PF) (8 items) and mental fatigue (MF) (6 items), totaling 14 items. Responses are scored using a binary system, with “no” answers scored as 0 and “yes” answers scored as 1. Items 10, 13, and 14 are reverse-scored. The total score ranges from 0 to 14, with higher scores indicating more severe fatigue.

2.3.6.4. Mood scale

The PANAS is used to assess an individual's positive and negative emotions.³⁷ The scale consists of 20 items divided into two dimensions: positive affect and negative affect. A 5-point Likert scale (ranging from 1 to 5) is used for scoring. Higher scores in positive affect indicate feelings of energy, focus, and happiness, while higher scores in negative affect reflect subjective feelings of distress and unhappiness.

2.3.7. Power analysis

A post hoc power analysis was performed using G∗Power software (version 3.1). This analysis was based on the Group × Time interaction effect on the PSQI, with η²_p of 0.67, an alpha level of 0.05, and a total sample size of 20. The results indicated an observed statistical power of 0.99 for this study, which exceeded the conventional threshold of 0.80. This demonstrates that the study had sufficient power to detect a significant cTBS effect.

2.4. Statistical analysis

All data from the participants were statistically analyzed using SPSS software (version 26.0). The experimental data are presented as the mean ± standard deviation (Mean ± SD). The normality of the data distribution for tested variables was assessed using the Shapiro-Wilk test. Differences in baseline characteristics and pre-cTBS measures between the cTBS and sham-cTBS groups were compared using independent samples t-tests or Mann-Whitney U tests, as appropriate. A 2 (Group: cTBS vs. sham-cTBS) × 2 (Time: pre-cTBS vs. post-cTBS) mixed-factorial analysis of variance (ANOVA) was conducted to examine the effects of cTBS and sham-cTBS on the outcome measures. In cases where a significant Group × Time interaction was observed, simple effects analysis was performed. All statistical analyses were based on two-tailed hypothesis testing, with the significance level set at α = 0.05. A P-value <0.05 was considered statistically significant. Effect sizes in the mixed-factorial ANOVA were assessed using partial eta-squared (η²_p). The effect size for η²_p was interpreted as follows: η²_p ≥ 0.01 indicates a small effect; η²_p ≥ 0.06 represents a medium effect; and η²_p ≥ 0.14 corresponds to a large effect.

3. Result

3.1. Effects of cTBS on sleep quality in athletes with SD

The results showed that there were no significant differences in any sleep quality indicators at baseline prior to cTBS. For SOL, a significant interaction effect between group and time was found [F_(1,18) = 35.57, P < 0.001, η²_p = 0.66], suggesting that the effect of cTBS type on SOL duration varied significantly across time. Simple effects analysis revealed that SOL decreased significantly in the cTBS group after cTBS compared to baseline (P < 0.001, MD = 10.80, 95 %CI [8.41, 13.19]), while no significant change was observed in the sham-cTBS group (P = 0.31, MD = 1.20, 95 %CI [−1.91, 3.59]). Furthermore, post-cTBS SOL was significantly lower in the cTBS group than in the sham-cTBS (P = 0.002, MD = −6.20, 95 %CI [−9.88, −2.52]).

For TST, a significant interaction effect between group and time was identified [F_(1,18) = 10.62, P = 0.004, η²_p = 0.37], suggesting that the effect of cTBS type on TST varied significantly across time points. Simple effects analysis revealed that TST significantly increased in the cTBS group after cTBS compared to baseline (P < 0.001, MD = −51, 95 %CI [−76.26, −25.74]), whereas no significant change was observed in the sham-cTBS group (P = 0.72, MD = 4.4, 95 %CI [−20.86, 29.66]). Additionally, post-cTBS TST was significantly higher in the cTBS group than in the sham-cTBS (P < 0.001, MD = 52.70, 95 %CI [27.84, 77.56]).

For TA, a significant interaction effect between group and time was identified [F_(1,18) = 17.12, P < 0.001, η²_p = 0.49], suggesting that the effect of cTBS type on TA varied significantly across different time points. Simple effects analysis revealed that TA decreased significantly in the cTBS group following cTBS compared to baseline (P < 0.001, MD = 24.30, 95 %CI [15.29, 33.31]). In contrast, no significant change was observed in the sham-cTBS group (P = 0.85, MD = −0.80, 95 %CI [−9.81, 8.21]). Additionally, post-cTBS TA was significantly lower in the cTBS group than in the sham-cTBS group (P < 0.001, MD = −22.60, 95 %CI [−29.40, −15.79]).

For the SFI, no significant effects were observed: the main effect of time [F_(1,18) = 0.47, P = 0.50, η²_p = 0.03], the main effect of group [F_(1,18) = 0.20, P = 0.66, η²_p = 0.01], and the interaction effect between group and time [F_(1,18) = 0.14, P = 0.71, η²_p = 0.008] were all non-significant (Table 2).

Table 2.

Effects of cTBS on sleep quality (M±SD).

	cTBS		Sham-cTBS			F	df	P	η2p
	pre-cTBS	post-cTBS	pre-cTBS	post-cTBS
SOL/min	33.60 ± 5.02	22.80 ± 3.16∗∗∗	30.20 ± 2.86	29.00 ± 4.55##	Time	55.58	(1,18)	0.001	0.76
					Group	0.77	(1,18)	0.39	0.04
					Time × group	35.57	(1,18)	0.001	0.66
TST/min	397.60 ± 19.47	448.60 ± 30.70∗∗∗	400.30 ± 32.90	395.90 ± 21.40###	Time	7.51	(1,18)	0.01	0.29
					Group	8.83	(1,18)	0.008	0.33
					Time × group	10.62	(1,18)	0.004	0.37
TA/min	30.80 ± 16.14	6.50 ± 5.28∗∗∗	28.30 ± 10.72	29.10 ± 8.79###	Time	15.00	(1,18)	0.001	0.46
					Group	6.82	(1,18)	0.02	0.28
					Time × group	17.12	(1,18)	0.001	0.49
SFI/%	31.35 ± 14.59	26.54 ± 16.13	27.67 ± 11.75	26.29 ± 13.55	Time	0.47	(1,18)	0.50	0.03
					Group	0.20	(1,18)	0.66	0.01
					Time × group	0.14	(1,18)	0.71	0.008

SOL: sleep onset latency; TST: total sleep time; TA: time awake; SFI: sleep fragmentation index.

∗∗∗ = Significant differences between pre-cTBS and post-cTBS conditions (P < 0.001).

## = Significant differences between the cTBS group and the sham-cTBS group (P < 0.01).

### = Significant differences between the cTBS group and the sham-cTBS group (P < 0.001).

3.2. Effects of cTBS on athletic performance in athletes with SD

3.2.1. Agility

The results showed that there was no significant difference in T-test performance time between the two groups at baseline prior to cTBS (t (18) = -0.17, P = 0.87). Mixed-factorial ANOVA revealed a significant interaction effect between group and time was observed [F_(1,18) = 6.35, P = 0.02, η²_p = 0.26], suggesting that the effect of cTBS type on T-test performance time differed across time points. Simple effects analysis showed that T-test performance time decreased significantly in the cTBS group after cTBS compared to baseline (P = 0.002, MD = 0.39, 95 %CI [0.17, 0.62]), while no significant change was found in the sham-cTBS group (P = 0.93, MD = 0.01, 95 %CI [−0.22, 0.24]). Furthermore, post-cTBS T-test performance time was significantly shorter in the cTBS group than in the sham-cTBS group (P = 0.03, MD = −0.42, 95 %CI [−0.79, −0.05]) (Fig. 3).

Fig. 3.

Effect of cTBS on Agility

∗∗ = Significant differences between pre-cTBS and post-cTBS conditions (P < 0.01);

# = Significant differences between the cTBS group and the sham-cTBS group (P < 0.05).

3.2.2. Standing long jump test

The results indicated that there was no significant difference in standing long jump distance between the two groups at baseline prior to stimulation (t(18) = -0.13, P = 0.90). Mixed-factorial ANOVA revealed that neither the main effect of time [F_(1,18) = 1.59, P = 0.22, η²_p = 0.08], the main effect of group[F_(1,18) = 0.001, P = 1.00, η²_p = 0.001], nor the interaction effect between group and time [F_(1,18) = 0.29, P = 0.60, η²_p = 0.02] was statistically significant (Table 3).

Table 3.

Effect of cTBS on standing long jump performance.

	cTBS		Sham-cTBS			F	df	P	η2p
	pre-cTBS	post-cTBS	pre-cTBS	post-cTBS
Length (cm)	268.53 ± 15.00	271.60 ± 15.85	269.47 ± 16.15	270.70 ± 16.97	Time	1.59	(1,18)	0.22	0.08
					Group	0.001	(1,18)	1	0.001
					Time × group	0.29	(1,18)	0.60	0.02

3.3. Effects of cTBS on reaction speed in athletes with SD

The results indicated no significant difference in reaction speed between the two groups at baseline prior to stimulation (t(18) = -0.09, P = 0.93). Mixed-factorial ANOVA revealed that neither the main effect of time [F_(1,18) = 3.33, P = 0.09, η²_p = 0.16], the main effect of group [F_(1,18) = 2.41, P = 0.14, η²_p = 0.12], nor the interaction effect between group and time [F_(1,18) = 3.55, P = 0.08, η²_p = 0.17] reached statistical significance (Table 4).

Table 4.

Effect of cTBS on reaction speed.

	cTBS		Sham-cTBS			F	df	P	η2p
	pre-cTBS	post-cTBS	pre-cTBS	post-cTBS
Time (ms)	324.03 ± 22.19	303.80 ± 14.73	324.97 ± 23.93	325.30 ± 18.92	Time	3.33	(1,18)	0.09	0.16
					Group	2.41	(1,18)	0.14	0.12
					Time × group	3.55	(1,18)	0.08	0.17

3.4. Effects of cTBS on subjective perceptions in athletes with SD

3.4.1. Effects of cTBS on subjective sleep quality in athletes with SD

The results indicated no significant difference in subjective sleep quality scores between the two groups at baseline prior to cTBS (t(18) = 0.79, P = 0.44). Mixed-factorial ANOVA revealed a significant interaction effect between group and time was found [F_(1,18) = 36.78, P < 0.001, η²_p = 0.67], suggesting that the effect of cTBS type on subjective sleep quality scores differed significantly across time points. Simple effects analysis showed that subjective sleep quality scores decreased significantly in the cTBS group after cTBS compared to baseline(P < 0.001, MD = 8.70, 95 %CI [6.50, 10.91]). In contrast, no significant change was observed in the sham-cTBS group (P = 0.78, MD = −0.30, 95 %CI [−2.51, 1.91]). Additionally, post-cTBS subjective sleep quality scores were significantly lower in the cTBS group than in the sham-cTBS group (P < 0.001, MD = −8.00, 95 %CI [−9.93, −6.07]) (Fig. 4).

Fig. 4.

Effect of cTBS on Subjective Sleep Quality

∗∗∗ = Significant differences between pre-cTBS and post-cTBS conditions (P < 0.001);

### = Significant differences between the cTBS group and the sham-cTBS group (P < 0.001).

3.4.2. Effects of cTBS on daytime sleepiness in athletes with SD

The results showed no significant difference in daytime sleepiness scores between the two groups at baseline prior to cTBS (t(18) = 0.00, P = 1.00). Mixed-factorial ANOVA revealed a significant main effect of time [F_(1,18) = 16.67, P < 0.001, η²_p = 0.48], indicating that daytime sleepiness scores decreased significantly after cTBS compared to pre-cTBS levels. However, neither the main effect of group [F_(1,18) = 0.30, P = 0.59, η²_p = 0.02] nor the interaction effect between group and time [F_(1,18) = 1.58, P = 0.23, η²_p = 0.08] reached statistical significance (Table 5).

Table 5.

Effect of cTBS on daytime sleepiness.

	cTBS		Sham-cTBS			F	df	P	η2p
	pre-cTBS	post-cTBS	pre-cTBS	post-cTBS
Score	12.70 ± 3.83	9.03 ± 3.30	12.70 ± 4.03	10.90 ± 2.92	Time	16.67	(1,18)	0.001	0.48
					Group	0.30	(1,18)	0.59	0.02
					Time × group	1.58	(1,18)	0.23	0.08

3.4.3. Effects of cTBS on fatigue perception in athletes with SD

The results indicated no significant difference in MF scores between the two groups at baseline prior to cTBS (t(18) = 0.95, P = 0.36). Mixed-factorial ANOVA revealed a significant interaction effect between group and time was observed [F_(1,18) = 13.74, P = 0.002, η²_p = 0.43], suggesting that the effect of cTBS type on MF scores varied significantly across time points. Simple effects analysis demonstrated that MF scores decreased significantly in the cTBS group after cTBS compared to baseline (P = 0.003, MD = 1.3, 95 %CI [0.50, 2.10]). In contrast, no significant change was found in the sham-cTBS group (P = 0.08, MD = −0.7, 95 %CI [−1.5, 0.1]). Additionally, post-cTBS MF scores were significantly lower in the cTBS group than in the sham-cTBS group (P = 0.003, MD = −1.6, 95 %CI [−2.57, −0.64]).

No significant difference was observed in PF scores between the two groups at baseline prior to cTBS (t(18) = 1.31, P = 0.21). A significant interaction effect between group and time was observed [F_(1,18) = 36.13, P < 0.001, η²_p = 0.67], suggesting that the effect of cTBS type on PF scores varied significantly across time points. Simple effects analysis revealed that PF scores decreased significantly in the cTBS group after cTBS compared to baseline (P < 0.001, MD = 3.00, 95 %CI [2.09, 3.91]). In contrast, no significant change was observed in the sham-cTBS group (P = 0.13, MD = −0.7, 95 %CI [−1.61, 0.21]). Additionally, post-cTBS PF scores were significantly lower in the cTBS group than in the sham-cTBS group (P = 0.002, MD = −2.8, 95 %CI [−4.39, −1.21]).

No significant difference was observed in total fatigue scores between the two groups at baseline prior to cTBS (t(18) = 1.51, P = 0.15). A significant interaction effect between group and time was observed [F_(1,18) = 34.61, P < 0.001, η²_p = 0.66], suggesting that the effect of cTBS type on total fatigue scores varied significantly across time points. Simple effects analysis revealed that total fatigue scores decreased significantly in the cTBS group after cTBS compared to baseline (P < 0.001, MD = 4.3, 95 %CI [2.86, 5.74]). In contrast, no significant change was observed in the sham-cTBS group (P = 0.06, MD = −1.4, 95 %CI [−2.84, 0.04). Additionally, post-cTBS total fatigue scores were significantly lower in the cTBS group than in the sham-cTBS group (P < 0.001, MD = −4.4, 95 %CI [−6.68, −2.12]) (Fig. 5).

Fig. 5.

Effect of cTBS on Subjective Fatigue Perception

∗∗= Significant differences between pre-cTBS and post-cTBS conditions (P < 0.01);

∗∗∗ = Significant differences between pre-cTBS and post-cTBS conditions (P < 0.001);

## = Significant differences between the cTBS group and the sham-cTBS group (P < 0.01).

### = Significant differences between the cTBS group and the sham-cTBS group (P < 0.001).

3.4.4. Effects of cTBS on mood in athletes with SD

For positive affect, no significant difference was observed between the two groups at baseline prior to cTBS (t(18) = -0.45, P = 0.66). Mixed-factorial ANOVA revealed that neither the main effect of time [F_(1,18) = 0.19, P = 0.67, η²_p = 0.01], the main effect of group[F_(1,18) = 0.001, P = 0.98, η²_p = 0.001], nor the interaction effect between group and time [F_(1,18) = 1.72, P = 0.21, η²_p = 0.09] reached statistical significance.

For negative affect, no significant difference was observed between the two groups at baseline prior to cTBS (t(18) = -0.10, P = 0.93). Similarly, the main effect of time [F_(1,18) = 2.97, P = 0.10, η²_p = 0.14], the main effect of group [F_(1,18) = 2.50, P = 0.13, η²_p = 0.12], and the interaction effect between group and time [F_(1,18) = 2.17, P = 0.16 η²_p = 0.11] were all non-significant (Table 6).

Table 6.

Effect of cTBS on subjective mood.

	cTBS		Sham-cTBS			F	df	P	η2p
	pre-cTBS	post-cTBS	pre-cTBS	post-cTBS
Negative mood score	25.10 ± 8.18	18.70 ± 5.08	25.40 ± 5.74	24.90 ± 6.23	Time	0.19	(1,18)	0.67	0.01
					Group	0.001	(1,18)	0.98	0.001
					Time × group	1.72	(1,18)	0.21	0.09
Positive mood score	31.40 ± 5.56	32.10 ± 4.31	32.50 ± 5.32	31.10 ± 4.18	Time	2.97	(1,18)	0.10	0.14
					Group	2.5	(1,18)	0.13	0.12
					Time × group	2.17	(1,18)	0.16	0.11

4. Discussion

4.1. Effects of cTBS on sleep quality in athletes with SD

Normal and sufficient sleep is a critical component of physical recovery for athletes. However, poor sleep quality or insufficient sleep can impair recovery, weaken the immune and endocrine systems, negatively affect cognitive function and decision-making, and increase the risk of injury. Among athletes, SD are frequently observed due to factors such as high-intensity training, training schedules, and emotional states. Common manifestations of SD in athletes include TST of less than 7 h, reduced sleep satisfaction, prolonged SOL, daytime sleepiness, fatigue,⁷ and a decline in subjective sleep quality. Currently, the exact causes of SD remain unclear. The prevailing view suggests that the primary cause of SD is a disruption in the sleep-wake regulatory mechanism.^38,39 Additionally, disturbances in the neural pathways between nuclei, as well as imbalances in neurotransmitters, related neurons, and receptors, are considered direct contributing factors,⁴⁰ Among these, serotonin 5-hydroxytryptamine (5-HT) and gamma-aminobutyric acid (GABA) are particularly important neurotransmitters implicated in sleep regulation.^41,42

In clinical practice, rTMS is often used to treat patients with SD and improve their quality of life.⁴³ As a short-duration and effective method for modulating cortical excitability, cTBS has garnered significant attention. This study employed a stimulation protocol of once daily for five consecutive days to investigate the effects of cTBS on sleep quality in individuals with SD. The results of the study indicate that cTBS can reduce SOL and TA, while increasing TST in athletes with SD. Additionally, subjective sleep quality, as measured by the PSQI, improved following cTBS. The underlying mechanism may be attributed to the inhibitory effects of cTBS on cortical excitability. Specifically, cTBS has been shown to increase GABA concentrations in the stimulated cortex. As an inhibitory neurotransmitter, GABA further suppresses cortical excitability,¹⁶ thereby promoting sleep regulation in individuals with SD, enhancing non-rapid eye movement (NREM) sleep duration, and ultimately improving both sleep duration and quality.

4.2. Effects of cTBS on athletic performance in athletes with SD

High-intensity athletic training can negatively impact athletes' sleep quality, potentially leading to the development of SD.³ Simultaneously, the occurrence of SD can adversely affect athletes' athletic performance. Specifically, SD has been shown to impair aerobic capacity,⁴⁴ anaerobic capacity,⁴⁵ repeated sprint ability,⁴⁶ muscle strength,⁴⁶ and explosive power,⁴⁷ as well as sport-specific performance.¹¹ Research has shown that SD may increase the expression of muscle degradation proteins and muscle clock genes, impairing muscle function.⁴⁸ Additionally, SD can disrupt the normal recovery of muscle energy substrates,⁴⁶ leading to further loss of muscle function and ultimately affecting athletic performance. This is often manifested during competition or training as a decline in muscle strength and endurance. Furthermore, the occurrence of SD often leads to daytime mood disturbances and increased subjective fatigue perception in athletes, which may also contribute to the decline in athletic performance observed in athletes with SD.^49,50 In this study, assessments of agility and standing long jump performance were conducted both before and after the administration of cTBS in athletes. The test results revealed a significant reduction in T-test completion time among athletes following cTBS. The underlying reason may be attributed to the improvement in sleep quality following cTBS, which indirectly facilitated athletes' physical recovery and alleviated subjective fatigue perception. This, in turn, may have restored sprinting ability and muscle explosive power, thereby enhancing agility performance in athletes. This facilitates athletes (e.g., football players) in performing rapid stops, directional changes, and similar maneuvers more quickly during competition, thereby enhancing competitive performance. However, it is noteworthy that the results of the standing long jump distance in this study showed no significant improvement in performance following cTBS. This may be due to the relatively short duration of sleep improvement at the time of testing, making it difficult to observe significant changes in a single-effort task like the standing long jump. Nevertheless, the cTBS group exhibited a trend of increased standing long jump performance after cTBS. Future studies could incorporate longer follow-up periods to further investigate these effects.

4.3. Effects of cTBS on reaction speed in athletes with SD

Reaction speed is influenced by various factors, including the neurofunctional state of the athlete. SD can impair the recovery of mental energy, leading to prolonged reaction times. Even short-term disruptions in sleep can result in slower reaction times in athletes.⁵¹ Furthermore, the impairment of cognitive function caused by SD not only reduces athletes' judgment and decision-making abilities,⁵² but also negatively affects reaction speed.⁵³ This impact is particularly pronounced in sports that require a high level of cognitive engagement. Research has shown that adequate sleep helps restore neural and metabolic depletion caused by wakefulness,⁵⁴ improving athletes' reaction speed and athletic performance.⁵⁵ However, statistical analysis revealed that the interaction effect between time and group was not statistically significant in terms of reaction time.

4.4. Effects of cTBS on daytime perception in athletes with SD

During high-intensity training, deteriorating emotional states or excessive psychological stress can lead to significant daytime sleepiness⁵⁶ and increased subjective fatigue.⁵⁷ Research has shown that nighttime SD significantly impact daytime quality of life, and chronic SD can lead to pronounced daytime fatigue.^7,58 The evaluation of therapeutic efficacy for SD typically encompasses two aspects: improvement in overall sleep quality and, equally importantly, concurrent enhancement of daytime perception. This study found that cTBS not only improved overall sleep quality in athletes with SD, as evidenced by enhanced subjective sleep quality (Fig. 4), increased TST, and reduced SOL and TA (Table 2), but also positively influenced daytime perception, including reductions in fatigue and daytime sleepiness. The study found that daytime sleepiness scores decreased significantly in the real cTBS stimulation group, a result consistent with previous research indicating that actively extending sleep duration improves daytime sleepiness in athletes.⁵⁵ Additionally, in terms of fatigue perception, cTBS not only improved overall fatigue in athletes with SD but also simultaneously alleviated both MF and PF.

4.5. Effects of cTBS on mood in athletes with SD

Mood is a significant factor influencing athletes' sleep quality,⁵ and the occurrence of SD can lead to noticeable emotional dysregulation and a decline in positive emotions.^46,53 The underlying mechanism may be attributed to the role of rapid eye movement (REM) sleep in emotional regulation.⁵⁹ In athletes with SD, the reduction in REM sleep duration weakens the regulatory effect of sleep on mood, creating a vicious cycle where negative emotions further impair sleep quality.

Reduced blood flow perfusion in the left DLPFC is one of the significant factors contributing to mood disorders.⁶⁰ Low-frequency rTMS can transiently influence cerebral blood flow, reducing blood flow in the ipsilateral middle cerebral artery while increasing blood flow in the contralateral side.⁶¹ Therefore, applying low-frequency rTMS to the right DLPFC can improve blood flow perfusion in the left DLPFC, thereby enhancing mood regulation. Additionally, the right DLPFC is a commonly targeted region for TMS in the treatment of depression.⁶² The cTBS protocol achieves effects similar to those of rTMS in inhibiting cortical excitability but in a shorter time frame. As a result, it is often employed as an effective approach for alleviating mood disorders and treating depression.⁶² Furthermore, studies have shown that cTBS can modulate alpha brain waves and enhance synaptic function in the prefrontal cortex, thereby improving mood.^63,64 However, it is noteworthy that the present study found no significant effect of cTBS on improving mood in athletes with sleep disorders, although a decreasing trend in negative emotion scores was observed in the cTBS group.

5. Study limitations and future directions

This study innovatively employs cTBS, characterized by its short cTBS duration, to improve sleep quality in SD athletes, while also monitoring subsequent changes in their athletic performance and subjective perceptions. It offers a novel approach for enhancing sleep quality in this population, demonstrating significant practical implications. Furthermore, it suggests a new direction for the application of cTBS in managing SD.

However, this study has several limitations. Notably, to avoid the potential confounding influence of the female menstrual cycle on physiological, psychological, and sleep-related outcomes, only male athletes were included as participants. Future research should include more detailed investigations involving both male and female athletes. Secondly, due to the lack of exploration into underlying mechanisms, the reasons for the observed changes in athletic performance and subjective perceptions remain unclear. Future studies should delve deeper to elucidate the mechanisms responsible for these changes. Furthermore, this study only assessed changes in various indicators before and after cTBS without conducting follow-up studies on the SD athletes. Future research should include follow-up assessments to explore the temporal effects of cTBS.

6. Conclusion

A five-day course of cTBS significantly improved subjective sleep quality, increased TST, reduced SOL and TA, enhanced agility, and ameliorated subjective fatigue perception in athletes with SD.

Informed consent

The privacy rights of human subjects have been observed and informed consent was obtained from all participants.

Research involving human participants

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the Declaration of Helsinki. This study was approved by the Beijing Sport University Ethics Committee (2023277H).

Funding

This work was supported by grants from the National Key R&D Program of China (2018YFF0300801), and the Fundamental Research Funds for the Central Universities (2025042).

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

The data is available from the corresponding author upon request.