This study will examine how two recovery methods-pneumatic compression (PC) applied to the legs and transcranial direct current stimulation (tDCS) applied to the head-help athletes recover after a 10-kilometer (10K) run. It also aims to find out which methods may help master athletes recover faster, maintain performance, and reduce the risk of injury.

Men aged 40-55 who are trained long-distance runners can participate, provided they do not have medical conditions that prevent safe exercise or use of the recovery methods. Participants will run 10K and then receive one of the following interventions in a randomized order: tDCS, PC, tDCS + PC, or no intervention (control). Each participant will experience all conditions, with a one-week break between sessions. Measurements will be taken before the run, immediately after, and after the intervention, including heart rate variability, cognitive tests (Stroop Test), vertical jump, and maximal voluntary muscle contraction, during which muscle activity will be recorded using electromyography (EMG). Data will be analyzed to compare how each intervention affects recovery, including physical performance, cognitive function, and psychological state.

The study will show which methods help master runners recover faster and more effectively, provide practical strategies to improve performance and reduce injury risk, and offer information on the separate and combined effects of tDCS and PC on recovery, which could help design age-specific recovery strategies for endurance athletes.

The aim of this study is to investigate the effects of combined transcranial direct current stimulation (tDCS) and pneumatic compression (PC) on recovery in master male runners following a 10-kilometer run. The study also aims to examine whether these interventions can shorten recovery time and prevent performance decline after prolonged and intense exercise.

This study will be conducted as a randomized, controlled, crossover trial using a mixed experimental design. Each participant will undergo four different recovery protocols in a randomized order, with a one-week interval between sessions. Randomization will be performed using Research Randomizer, assigning participants to one of four sequences (e.g., B-A-D-C). Participants will be identified only by numerical codes to ensure blinding and maintain confidentiality. Each participant will experience all protocols, allowing within-subject comparisons and minimizing order-related bias.

The four recovery protocols are:

(A) tDCS group: transcranial direct current stimulation only (B) PC group: pneumatic compression (PC) only (C) tDCS + PC group: simultaneous application of both tDCS and PC (D) Control group: passive rest with no intervention

The tDCS and PC interventions represent the independent variables, while dependent variables include the Well-being Questionnaire (WBQ), Total Quality Recovery (TQR), heart rate variability (HRV), Stroop Test performance, vertical jump height, and maximal voluntary isometric contraction (MVIC) with electromyography (EMG) recordings.

Participants will be 35 male long-distance master runners aged 40-55 years, residing in Bursa, Turkey, with at least five years of consistent training. Participants will train five days per week for approximately 90 minutes per day and must meet aerobic fitness criteria established by the American College of Sports Medicine, including completion of an official 10-kilometer race under 50 minutes within the past six months and maintenance of a weekly running volume of 60-80 kilometers. Volunteers will be recruited from the local long-distance running community familiar to the principal investigator, Hilal Oruç Kaya.

Participants will be excluded if they have used regular medications within the last six months; consumed stimulants, caffeine, or alcohol within 24 hours prior to testing; smoke; have experienced musculoskeletal injuries within the past six months; are currently undergoing physical therapy; or have neurological conditions such as epilepsy or a history of seizures, or possess cardiac, brain, or other electronic implants. Additional exclusion criteria include open wounds or dermatological conditions on the head, circulatory disorders such as deep vein thrombosis, peripheral arterial disease, severe varicose veins, or prior exposure to tDCS or PC interventions. Participants may withdraw voluntarily, fail to attend sessions, or be removed if cardiovascular, neurological, or orthopedic complications occur during exercise or interventions, or if they experience excessive discomfort or adverse effects from the tDCS or PC procedures. Written informed consent will be obtained after participants are informed about the study's purpose, procedures, potential risks, and benefits.

Sample size was calculated using G*Power version 3.1.9.7 for repeated-measures analysis of variance with within-between interaction, assuming an effect size of f = 0.30, an alpha level of 0.05, and a statistical power of 0.80, resulting in a required sample size of 28 participants. To account for potential dropouts, a total of 35 participants will be recruited.

Screening and Familiarization Session

Participants will undergo anthropometric measurements (body mass, body fat percentage, and height) using a Tanita BC 418 MA body composition analyzer and a Seca stadiometer. Physical fitness will be evaluated using a 12-minute Cooper Test conducted on a 400-meter outdoor track under controlled environmental conditions (temperature 20-24°C, relative humidity 50-70%, wind speed ≤10 km/h). A standardized 20-minute warm-up, including jogging, accelerations, jumps, and stretching exercises, will precede the test. Distances will be recorded using a Polar V3 global positioning system (GPS) watch.

Participants will also complete a familiarization session with the 10-kilometer running course, tDCS and PC devices, the Stroop Test, MVIC procedures, and vertical jump assessments to ensure understanding of all study procedures.

Experimental Sessions

Pre-run Measurements (T1): Participants will complete the Well-being Questionnaire (WBQ) and Total Quality Recovery (TQR) scales. Heart rate (HR) and heart rate variability (HRV) will be recorded for 10 minutes using a Polar V3 GPS watch and an H10 heart rate monitor. Cognitive performance will be assessed using the Stroop Test, vertical jump height will be measured, and MVIC of the quadriceps muscles will be recorded with electromyography (EMG).

10-Kilometer Run: Participants will complete a 10-kilometer run at 75% exercise intensity calculated using the Karvonen formula. Exercise intensity will be monitored using GPS and HR data. Perceived exertion will be assessed using the Borg 20-point Rating of Perceived Exertion scale at the 5-kilometer mark and immediately after completion of the run.

Post-run Measurements (T2): All measurements obtained at T1 will be repeated immediately after the 10-kilometer run.

Interventions

Participants will be randomly assigned to one of the four recovery protocols:

tDCS: 20 minutes of 2 mA stimulation applied to the F3 and F4 regions of the dorsolateral prefrontal cortex in a semi-reclined position using the Brain Premier device

PC: 20 minutes of sequential pneumatic compression applied to the lower limbs using the Normatec pneumatic compression system, with compression pressure adjustable between 20 and 100 mmHg, following standardized pressure and timing protocols

tDCS + PC: simultaneous application of both interventions for 20 minutes

Control: passive rest in a semi-reclined position for 20 minutes

Participants in the tDCS conditions will report sensations and perceived intensity of stimulation (e.g., itching, burning, discomfort) using a structured questionnaire.

Post-intervention Measurements (T3): All measurements obtained at T1 will be repeated immediately after the intervention.

Outcome Measures

Subjective recovery measures: Well-being Questionnaire (WBQ) and Total Quality Recovery (TQR)

Autonomic measures: heart rate variability (HRV) and GPS-derived data

Cognitive performance assessed using the Stroop Test

Vertical jump height assessed using the My Jump application

MVIC of the quadriceps muscles recorded with electromyography (EMG) following the Surface Electromyography for the Non-Invasive Assessment of Muscles (SENIAM) guidelines

Statistical Analysis

Data will be analyzed using IBM SPSS Statistics version 29. Normality will be assessed using the Shapiro-Wilk test, homogeneity of variances using Levene's test, and sphericity using Mauchly's test. A two-way repeated-measures analysis of variance (4 Time × 4 Condition) will be used to evaluate interaction effects, with Bonferroni-adjusted post hoc comparisons applied when appropriate. Effect sizes will be reported using partial eta squared (ηp²), with values of >0.01 considered small, >0.06 medium, and >0.14 large. Statistical significance will be set at p < 0.05.

Inclusion Criteria

• Age 40 to 55 years
• Completion of an official 10-kilometer race in under 50 minutes within the last six months
• Regular training 5 days per week, 90 minutes per day
• Weekly running volume of 60-80 kilometers
• Aerobic fitness ≥ 80% according to American College of Sports Medicine (ACSM) guidelines

Exclusion Criteria

• Use of regular medications within the last six months
• Consumption of stimulants, caffeine, or alcohol within 24 hours prior to testing
• Smoking
• Musculoskeletal injuries within the last six months
• Participation in current physical therapy programs
• Epilepsy or history of seizures
• Cardiac, brain, or other electronic implants
• Open wounds or dermatological conditions on the head
• Circulatory disorders, including deep vein thrombosis, peripheral arterial disease, or severe varicose veins
• Previous exposure to transcranial direct current stimulation (tDCS) or pneumatic compression (PC) interventions

Individual participant data (IPD) from this study will not be shared due to privacy concerns and the study's data management plan. All data will be used solely for the purposes of the current research and will not be made available to external researchers.