Inspiratory Muscle Activation and Post-Exercise Recovery in Professional Football Players

January 22, 2026 updated by: Sierra Varona SL

Acute Modulation of Post-Exercise Recovery Through Inspiratory Muscle Activation in Professional Male Football Players: A Randomized Clinical Trial

Respiratory muscles play a fundamental role in sports performance. Fatigue of these muscles induces changes in maximal inspiratory pressure and autonomic nervous system activity, thereby compromising the athlete's recovery process. The primary aim of this study is to evaluate the specific effects of different inspiratory muscle activation modalities on post-exercise recovery in professional male football players. The study seeks to determine which of the three modalities-bilateral phrenic nerve electrical stimulation, a threshold loading device protocol, or inactivity-provides greater benefits for recovery. The effectiveness of these interventions will be assessed using two key outcome variables: maximal inspiratory pressure (MIP) and heart rate variability (HRV).

This study is designed as a randomized clinical trial (RCT) in which participants will be allocated into three intervention groups: a bilateral phrenic nerve electrical stimulation group (EG1), in which involuntary diaphragmatic contractions will be induced using an electrotherapy device with current applied to the phrenic nerves; a threshold device group (EG2), in which participants will perform breathing against submaximal inspiratory loads equivalent to 40% of their MIP; and a control group (CG), which will remain seated for a period equivalent to the duration of the other interventions. Group allocation will be ensured through randomization using Microsoft Excel.

Regarding statistical analysis, data normality will be assessed using the Shapiro-Wilk test. Comparisons of quantitative variables will be performed using Student's t test when normality assumptions are met, or the Mann-Whitney U test otherwise. A p value < 0.05 will be considered statistically significant.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

30

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Male professional football player.
  • Currently under an active professional contract and participating in regular competition.
  • Aged between 18 and 40 years.
  • No participation in inspiratory muscle training (IMT) programs in the past 12 months.
  • Signed informed consent provided by the participant.

Exclusion Criteria:

  • Musculoskeletal injuries or surgical interventions within the past 6 months.
  • Use of medications affecting cardiac or respiratory function (e.g., beta-blockers, beta-adrenergic inhibitors).
  • Presence of any acute and/or chronic disease (cardiorespiratory, neurological, metabolic, oncological, etc.).
  • Use of tobacco, recreational drugs, or stimulant substances.
  • Metallic implants in the cervical region.
  • Presence of a pacemaker.
  • Current participation in other inspiratory muscle training programs.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Phrenic Electrostimulation

The participant will be placed in the supine position, and the intervention will be performed using a pen-type electrode. Bilateral stimulation of the phrenic nerves will be applied below the sternal portion of the sternocleidomastoid muscle at the C3-C5 level. The electrical stimulators will be set to a mean frequency of 50 Hz and a pulse width of 300 μs. Stimulation intensity will be progressively increased until a visible diaphragmatic contraction (abdominal movement) is observed and reaches the maximum level tolerable for the player.

The stimulation protocol will consist of two sets of 30 repetitions, delivered in bilateral cycles of 6 s ON (stimulation) and 10 s OFF (rest), including a 2-minute rest period between sets. Concurrently with the perception of the involuntary contraction, the participant will perform a voluntary contraction through diaphragmatic inspiration.
Device: Inspiratory muscle activation via phrenic nerve modulation
Phrenic nerve stimulation using low-frequency symmetric biphasic current
Active Comparator: Inspiratory muscle warm-up group

Participants will breathe against submaximal inspiratory loads following a protocol consisting of two sets of 30 breaths, equivalent to 40% of their MIP, using the Breathcare MIP/MEP device (Big Breathe®, GH Innotek Co., Ltd., Busan, Republic of Korea). Breathing will be performed using a self-paced pattern, provided that a ratio of approximately 1 s of inspiration to 2 s of expiration is maintained to avoid hyperventilation.

The session duration will correspond to the exact time required to complete the two sets of breaths, including a 2-minute rest period between sets, with an estimated total duration of approximately 15 minutes.
Device: Inspiratory muscle activation via threshold device
Deep inspirations against submaximal inspiratory load
No Intervention: Control group
Participants in this group will remain seated at rest in a quiet and controlled environment. During this period, they will breathe normally. The rest duration for this group will be identical to that of the other interventions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Hear rate variability
Time Frame: Pre-match 24 hours before (baseline); Post-match 24 hours (pre-intervention); Immediately post-intervention; 15 minutes post-intervention; 30 minutes post-intervention
HRV will be assessed using a heart rate monitor (Polar H10; Polar Electro Oy, Kempele, Finland) with participants in the supine position in a quiet room (~25 °C, dim lighting). Cardiac signals will be recorded for 3 minutes via a chest strap. Participants will avoid caffeine, alcohol, tobacco, and intense exercise for 12 h prior, and refrain from speaking or voluntary movements during recording. Analysis will be performed with Kubios HRV 3.1.0 (University of Kuopio, Finland), examining LF/HF ratio, LF (0.04-0.15 Hz) and HF (0.15-0.40 Hz) power in normalized units, SDNN, and RMSSD.
Pre-match 24 hours before (baseline); Post-match 24 hours (pre-intervention); Immediately post-intervention; 15 minutes post-intervention; 30 minutes post-intervention

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Maximal Inspiratory Pressure
Time Frame: Pre-match 24 hours before (baseline); Post-match 24 hours (pre-intervention); Immediately post-intervention; 15 minutes post-intervention; 30 minutes post-intervention
Maximal inspiratory pressure (MIP) will be assessed with participants in a seated position using the Breathcare MIP/MEP device (Big Breathe®, GH Innotek Co., Ltd., Busan, Republic of Korea). The examiner will demonstrate the maneuver prior to its execution. To ensure proper airflow through the mouth, the nostrils will be occluded. Participants will perform up to six maneuvers per attempt, with a 1-minute rest between each. The most consistent and reproducible result from three attempts, with a variation of less than 5%, will be selected for analysis.
Pre-match 24 hours before (baseline); Post-match 24 hours (pre-intervention); Immediately post-intervention; 15 minutes post-intervention; 30 minutes post-intervention

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sierra Varona SL

Collaborators

University of Alcala

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

January 20, 2026

Primary Completion (Estimated)

March 10, 2026

Study Completion (Estimated)

April 1, 2026

Study Registration Dates

First Submitted

January 8, 2026

First Submitted That Met QC Criteria

January 22, 2026

First Posted (Actual)

January 28, 2026

Study Record Updates

Last Update Posted (Actual)

January 28, 2026

Last Update Submitted That Met QC Criteria

January 22, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 021

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

The availability of the data, and the materials will be available at the request of the publisher.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • ANALYTIC_CODE
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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