Abstract
The optimization of descending motor commands from the central nervous system is essential for maximizing performance during short-distance running. Recent studies have shown that transcranial direct current stimulation (tDCS) can modulate central nervous system excitability and enhance exercise performance. Additionally, plyometric exercise is known to enhance instantaneous motor performance. However, the combined effects of tDCS and plyo- metric exercise remain poorly understood. Therefore, we investigated the combined effects of anodal tDCS and plyometric conditioning exercises on short-distance sprint running. Eleven university athletes were asked to perform a 20-meter sprint test both before (pre-test) and after tDCS (post-test). Before the pre-test, the participants engaged in jogging, stretching, and in- cremental 20-meter sprint exercises. After the pre-test, anodal tDCS was applied to the cortical leg area. Following tDCS, plyometric hopping exercises were performed, and a post-test was conducted. The intensity and duration of the stimulation were 2 mA and 15 min, respectively. Sham stimulations were performed on different days using the same experimental procedure. The post-test time was significantly shorter than the pre-test time in both the anodal and sham tDCS conditions. Further, the improvement rate in the post-test was significantly higher in the anodal tDCS condition than in the sham tDCS condition. These findings indicate that combined anodal tDCS and prior plyometric exercise can optimize descending motor commands and pe- ripheral motor function, thereby improving short-sprint running performance. Keywords : direct current stimulation, sprint running, conditioning exercise, plyometric exercise, neuromodulation Introduction Instantaneous sprinting ability is a critical factor affect- ing athletic performance in various sports. As such, elu- cidating the mechanisms that enable high-intensity sprint performance and developing appropriate training methods are important research topics in sports sciences. Sprint performance is not determined solely by the function of peripheral organs such as muscles and tendons. Indeed, when running speed
neuromodulation Introduction Instantaneous sprinting ability is a critical factor affect- ing athletic performance in various sports. As such, elu- cidating the mechanisms that enable high-intensity sprint performance and developing appropriate training methods are important research topics in sports sciences. Sprint performance is not determined solely by the function of peripheral organs such as muscles and tendons. Indeed, when running speed increases, the patterns of muscle activity and sensory feedback may change continuously; consequently, muscle activity increases 1,2) . In other words, appropriate descending commands transmitted from the central nervous system (CNS) to the muscles are essential for maximizing sprint performance 3) . Despite their simplicity, conditioning exercises per- formed immediately prior to a motor task are known to modulate descending commands, thereby facilitating sub- sequent motor performance. Rapid finger abduction over a few minutes results in changes in the muscle activity patterns and CNS excitability, thereby improving move- ment acceleration 4) . Improvements in sprint performance occur after movements that require instantaneous and large-force production 5) . These findings suggest that the CNS does not necessarily continually optimize motor out- put. Therefore, appropriate conditioning exercises could potentiate peripheral functions and refine descending commands from the CNS to the muscles, which would 1 Faculty of Nutritional Science, Sagami Women’s University, 2-1-1 Bunkyo, Minami-ku, Sagamihara-shi, Kanagawa 252-0383, Japan 2 Faculty of Education, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi, Chiba 263-8522, Japan 3 Department of Rehabilitation, Health Science University, 7187 Kodachi, Fujikawaguchiko-machi, Minamitsuru-gun, Yamanashi 401-0380, Japan 4 Faculty of Education, Keiai University, 1-5-21 Anagawa, Inage-ku, Chiba-shi, Chiba 263-8588, Japan *Correspondence: sasada_syusaku@isc.sagami-wu.ac.jp © 2025 The Japanese Society of Physical Fitness and Sports Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercialNoDerivatives license (https://creativecommons.org/licenses/by-nc-nd/4.0/).
102JPFSM: Sasada S, et al. maximize sprint performance. Transcranial direct current stimulation (tDCS) is a method to modulate descending commands, which in- volves the delivery of a weak direct current to the CNS via electrodes attached to the scalp for several minutes or longer to modify excitability 6) . Anodal stimulation, which involves placing an anode near the motor cortex, increas- es the amplitude of motor-evoked potentials (MEP) in the muscles associated with the stimulated area 7) and im- proves voluntary activation 8) . Anodal tDCS applied before exercise enhances toe grip strength 9) , and prolongs the du- ration of fatiguing exercise 10-12) . Therefore, if the descend- ing commands transmitted to the muscles during sprinting are not optimized, performance may be improved by prior anodal tDCS. Previous studies have reported the effects of anodal tDCS on sprint performance following a single bout of sprinting performance 10,13) . These studies evaluated sprint power during cycling after applying anodal tDCS; how- ever, the observed improvement in power was not signifi- cant 10,13) . Conditioning exercises are commonly performed prior to an event to maximize the performance in sports that require short-distance running or sprinting. The excit- ability-modulating effects of tDCS vary depending on the excitability of the CNS before and after stimulation 14,15) . As such, different effects of anodal stimulation from those of previous studies were observed in sprint performance after practical conditioning exercises. Therefore, this study investigated whether anodal tDCS applied after practical conditioning exercises could im- prove sprinting performance. One practical conditioning exercise used in this study was the plyometric exercise, which involves rapid stretching and contraction of mus- cles to produce vital force 16) ; it has also been reported to shorten sprint times 17) . In addition, repetitive high-force contractions modulate the CNS 4) . Thus, in this study, a plyometric-like hopping exercise was performed after an- odal stimulation and sprint times were compared between the stimulus conditions. Materials and Methods Participants. The participants included 11 healthy uni- versity athletes (5 men, 6 women; Table 1), all of whom were university track and field team
In addition, repetitive high-force contractions modulate the CNS 4) . Thus, in this study, a plyometric-like hopping exercise was performed after an- odal stimulation and sprint times were compared between the stimulus conditions. Materials and Methods Participants. The participants included 11 healthy uni- versity athletes (5 men, 6 women; Table 1), all of whom were university track and field team members affiliated with the Kanto Student Athletics Federation who engaged in daily training. This study was conducted in accordance with the Declaration of Helsinki and ethical guidelines for medical research involving human subjects, with the approval of the Chiba University Ethics Committee (ap- proval number: 38). Before the experiment, participants were provided with an explanation of the experimental procedure and purpose, and the experiment was conduct- ed after obtaining their consent to participate. In addition, prior to the experiment, we confirmed the presence of intracranial implants or surgical experience, and inquired about hospital visits or medication use related to psycho- logical symptoms. None of the participants met the exclu- sion criteria. Experimental Procedure. The participants performed two sets of experiments under anodal and sham tDCS conditions. A 20-meter sprint running test was conducted before and after tDCS with conditioning exercise. First, the participants performed conditioning exercises (pre- conditioning) with 5 min of jogging, 2 min of stretch- ing, 6 min of familiarization practice with the 20-meter sprint, and a 5 min break. Subsequently, they performed Table 1. Participant profiles Body weight and percentage of body fat (% fat) in all participants. Female: F, Male: M. Journal of Physical Fitness and Sports Medicine (JPFSM) ) 6 S U L Q W ) 6 S U L Q W ) 6 S U L Q W ) - X P S 0 6 S U L Q W 0 6 S U L Q W 0 6 S U L Q W 0 6 S U L Q W ) 6 S U L Q W 0 6 S U L Q W ) 6 S U L Q W 6 H [ % R G \ Z H L J K
6 S U L Q W 0 6 S U L Q W 0 6 S U L Q W 0 6 S U L Q W ) 6 S U L Q W 0 6 S U L Q W ) 6 S U L Q W 6 H [ % R G \ Z H L J K W N J Fat Sports $ Y H U D J H + H L J K W F P $ J H (yr) 6 X E & R G H
103JPFSM: Effect of direct current stimulation on sprint running a 20-meter sprint test (pre-test). Following the pre-test, tDCS was applied for 15 min while participants were seated. After tDCS was terminated, the participants per- formed plyometric-like hopping exercises (postcondition- ing). The hopping exercise consisted of 30 hopping steps for 150 s. Participants performed a sequence of five hop- ping steps with one leg, following which they switched to the opposite leg. This sequence was repeated three times with a 25 s duty cycle (Fig. 1). During the hopping exercise, the participants were instructed to “bounce as quickly as possible and jump as far horizontally as pos- sible.” After the hopping exercise, a 2.5 min break was taken, after which the participants performed the 20-meter sprint test (post-test) again. Prior to the above experiments, the participants were asked to answer a questionnaire regarding their physi- cal condition, and their body composition was measured using a body composition meter (InnerScan DUAL, TANITA, Japan). The two sets of experiments were con- ducted on separate days, with a minimum interval of 48 h between each set. The 20-meter sprint test was conducted outdoors on a track and field ground, and all tests were performed on the same surface. The participants used the same shoes for both measurements in the 20-meter sprint test. A mobile device application (Sprint Timer Pro, Sten Kaiser, Sweden) was used to measure the time required for the 20-m sprint test. A loudspeaker was placed ~50 cm in the starting position, and after the words “on your mark” and “set,” a beep sound was delivered randomly within the range of “2 - 3 s”. The participants performed a full-effort sprint in response to beeps. A camera was installed at the goal point, and the time was measured in units of 0.01 seconds by photo judgment. The time from the start of the sound signal to crossing of the finish line was measured. Before the pre-test, all participants en- gaged in two practice sessions of incremental 20-meter sprint with audio cues. Time was measured during these practice sessions to ensure that all
point, and the time was measured in units of 0.01 seconds by photo judgment. The time from the start of the sound signal to crossing of the finish line was measured. Before the pre-test, all participants en- gaged in two practice sessions of incremental 20-meter sprint with audio cues. Time was measured during these practice sessions to ensure that all were familiar with the measurement protocols. Transcranial direct current stimulation (tDCS). tDCS was performed according to previous studies 10,13,18) . The stimulation device used was a DC-STIMULATOR (Neu- roConn, Germany) with a rubber electrode (5 × 7 cm, 35 cm 2 ) covered with a sponge soaked in physiological saline. The anode was placed at the vertex (Cz) and the cathode was placed at the center of the forehead. The stimuli consisted of anodal and sham stimulations. Anodal stimulation was applied at an intensity of 2mA (current density of 0.057 mA/cm 2 ) for 15 min, with a fade-in/fade- out time of 15 s. In the sham stimulus condition, the cur- rent was increased to 2 mA for the 15 s fade-in time and then immediately decreased to 0 mA for the 15 s fade-out time. During both stimulus conditions, the participants were instructed to immediately report any itching, dis- comfort, or pain. However, there were no such reports during the experiment. The tDCS-induced electrical fields were estimated us- ing a free and open-source software package designed to simulate noninvasive brain stimulation (SimNIBS v.4.1.0), which can create a volume conductor model and perform electric field simulations from segmented MRI images 19) . Fig. 2 presents the simulated spatial distribution of the electrical field with its default parameters and the head model (m2m_MNI152). The electrode size and current intensity corresponded to the aforementioned tDCS pa- rameters. The center positions of the anode and cathode were set as Cz and Fpz, respectively. Statistical analysis. Statistical analyses were performed using SPSS software (Statistics 25 and 27, IBM, Japan; JASP 0.19, University of Amsterdam, Netherlands). A two-way analysis of variance (ANOVA) with repeated measures was conducted to compare the 20-m sprint times before and
the aforementioned tDCS pa- rameters. The center positions of the anode and cathode were set as Cz and Fpz, respectively. Statistical analysis. Statistical analyses were performed using SPSS software (Statistics 25 and 27, IBM, Japan; JASP 0.19, University of Amsterdam, Netherlands). A two-way analysis of variance (ANOVA) with repeated measures was conducted to compare the 20-m sprint times before and after the intervention (pre-test vs. post- test) and between the stimulus conditions (anodal vs. Fig. 1 Experimental timeline. Motor tasks and inter-intervals are represented as boxes and arrows, respectively. Solid bold boxes indicate an example timeline of hopping task when subject initiates hopping using left leg. Figure 1 Pre conditioning Pre test Hopping Post test 5min tDCS 15 min 2.5 min 5 steps Ex) left leg start 25s Right Left 150s footstep
104JPFSM: Sasada S, et al. Results Fig. 3A shows the grand means and standard deviations of the 20-m sprint time for each stimulus condition. The average time for the anodal stimulus condition was 3.85 ± 0.10 s before stimulation (pre-time) and 3.78 ± 0.13 s after stimulation (post-time). The pre-time for the sham stimulus condition was 3.85 ± 0.14 s, and the post-time was 3.82 ± 0.15 s. A significant main effect of the stimu- lation intervention (pre- vs. post-time) was found using repeated measures of two-way ANOVA (F (1,10) = 21.406, p = 0.001, partial η 2 = 0.682). However, the stimulus condition (anode vs. sham) showed no significant main effect (F (1,10) = 0.515, p = 0.489, partial η 2 = 0.049). A significant interaction was found between stimulus inter- vention and condition (F (1,10) = 5.998, p = 0.034, partial η 2 = 0.375). The post-time was significantly shorter than the pre-time in both the anodal (p = 0.019) and sham stimulus conditions (p = 0.010), using Bonferroni’s post hoc test. In contrast, the two stimulus conditions showed no sig- nificant differences in either the pre-time (p = 1.000) or the post-time (p = 1.000). Fig. 3B shows the degree of change in the post-time compared to the pre-time. Positive values indicate an increase in time (performance deterioration), while nega- tive values indicate a reduction in time (performance improvement). The differences between the anodal and sham stimulus conditions were -1.76 ± 1.50% and -0.69 ± 0.54%, respectively, and the difference between the stimulus conditions was significant (t = 2.476, p = 0.033, Cohen’s d = 0.746). Fig. 4 shows a scatter plot of the relationship between the pre-time (x-axis) and the degree of change in time after tDCS stimulation (y-axis). Each plot represents the data for an individual participant, and the grey dashed line represents the linear regression line obtained from these data. There was no significant relationship between the pre-time and the degree of change post-time for either stimulus condition. Discussion This study investigated the effects of anodal tDCS on sprint running performance following plyometric condi-
tDCS stimulation (y-axis). Each plot represents the data for an individual participant, and the grey dashed line represents the linear regression line obtained from these data. There was no significant relationship between the pre-time and the degree of change post-time for either stimulus condition. Discussion This study investigated the effects of anodal tDCS on sprint running performance following plyometric condi- tioning exercise. The 20-meter sprint requires the rapid coordination of the four limb muscle groups at the start of the sprint. As such, this type of sprint has been used to verify the athletic conditions in the intervention effect of plyometric exercise 20) . The results showed that the 20-m sprint time following anodal tDCS was significantly shortened compared to the sham stimulus condition. Previous studies have also examined the effect of anodal tDCS on sprinting and reported a reduction in the degree of time decrease during a 15-m sprint after pre-exercise anodal stimulation 21) . However, they did not compare the time immediately following stimulation, and thus found Fig. 2 Simulated spatial distribution of electrical field by Sim- NIBS v4.1.0. Color density indicates magnitude of elec- trical field. Positions of tDCS electrodes are represented as rectangular floating objects. Bottom panel depicts sag- ittal plane placed approximately at fissura longitudinalis cerebri using clipping tool of Gmsh (default view [1]). Figure 2 0.000 0.435 2 Magnitude of the electric eld (V/m ) sham stimulation). The degrees of freedom were adjusted using the Greenhouse–Geisser epsilon, depending on the sphericity of the data. Bonferroni’s multiple comparison test was conducted as a post-hoc test to determine the main effects and interactions. A paired t-test was applied to compare the changes in the post-test relative to the pre- test between stimulus conditions. Pearson’s correlation coefficient was calculated between the mean pre-time and the degree of change in both stimulus conditions. The mean pre-time was averaged as the pre-time between the sham and anodal stimulus conditions. The significance level was set at less than 5% for all tests.
was calculated between the mean pre-time and the degree of change in both stimulus conditions. The mean pre-time was averaged as the pre-time between the sham and anodal stimulus conditions. The significance level was set at less than 5% for all tests.
105JPFSM: Effect of direct current stimulation on sprint running no differences in sprint times between the 1st-10th and 11th-20th sprints after stimulation. In the present study, two sprint runs, tDCS stimulation and hopping exercises, were performed under each stimulus condition at intervals of approximately 20 min. Concerning the anodal tDCS and sham conditions, the post-time was significantly shorter than the pre-time in the anodal tDCS group (Fig. 3A). Thus, this study is the first to show an improvement in sprint performance due to the combination of condi- tioning plyometric exercise and anodal tDCS. As a practical conditioning exercise, one-leg hopping was performed after tDCS. Plyometric exercises such as hopping are conditioning exercises that improve sprint performance 17) . Performing plyometric exercises increases the maximum muscle contraction force because of muscle contraction reinforcement, known as post-activation potentiation 22) . Plyometric conditioning may alter the ef- ficiency of synaptic transmission at the neuromuscular junction 23) . In addition, the phosphorylation of myosin- regulated light chains in the excitation-contraction link- age could affect exercise performance by increasing the sensitivity of actomyosin to calcium ions 24) . Additionally, repeated brief and intensive force production improves muscle activity patterns 4) , and potentially increases volun- tary activation 16,25) . Based on previous studies, the imme- diate effects of this conditioning exercise may refine both peripheral and central factors. In this study, hopping was performed as a conditioning exercise before the post-test. The results showed a significant reduction in post-time compared to pre-time, even under the sham stimulus con- dition (Fig. 3A), which is consistent with the conditioning effect of plyometrics reported in previous studies 17) . If anodal tDCS was applied before the hopping exer- cise, the subsequent post-time was significantly shortened compared to sham stimulation. Several central mecha- nisms must be considered to explain the findings of this study. For example, tDCS affects the concentration of GABA, a primary inhibitory neurotransmitter, as well as Fig. 3 A: Averaged time of short sprint running before (pre) and after (post) transcranial direct current stimulation in each stimulus condition. B: Degree of change in time with respect
Description
This research explores how tDCS and hopping exercises improve sprint performance.