An interventional study of Inspiratory muscle activation via phrenic nerve modulation and Inspiratory muscle activation via threshold device in Sports Physical Therapy and Injury;Sports, sponsored by Sierra Varona SL. Not yet recruiting. Open to male participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-01-28.
Sponsored by Sierra Varona SL · Not applicable, Interventional, and Treatment
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.
258 studies on the registry are indexed under Athletic Injuries; 45 are open to participants now.
This study's planned enrollment of 30 is below the median of 44 across 164 interventional studies indexed under Athletic Injuries.
Browse Athletic Injuries studies →Sierra Varona SL is the lead sponsor of 16 studies on the registry; 16 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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
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
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.
Phrenic nerve stimulation using low-frequency symmetric biphasic current
Deep inspirations against submaximal inspiratory load
Hear rate variability
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.
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
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.
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
No study locations are listed for this record.
Plan to share: Yes — The availability of the data, and the materials will be available at the request of the publisher.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report, Analytic code
No publications or documents are linked to this record.
Start is estimated for Jan 2026; primary completion for Mar 2026, 1 month later.
Of 119 non-industry interventional studies with no phase under Athletic Injuries, half reached primary completion within 5 months of starting (the median), counting those still running; a quarter within 2 and three quarters within 14. This study's planned 1 month is below that.
Counting every sponsor, half of 121 studies reached it within 5 months; a quarter within 2 and three quarters within 14.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in Jan 2026. You cannot join it, but the record below documents what was studied.
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