Physical Performance ParametersNCT07475078
Reactive Strength and Dynamic Rebound: A Drop Jump Index Comparison
A study testing Drop Jump Protocol in people with Physical Performance Parameters, run by University Institute of Maia at 1 site in Portugal.
Trial summary
The stretch-shortening cycle (SSC) is a fundamental mechanism in explosive human movement, enabling musculotendinous units to store and release elastic energy, thereby allowing the body to produce higher forces and velocities with greater mechanical efficiency. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Physical Performance Parameters
- What is being tested?
- Drop Jump Protocol
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 50 participants
- Where
- 1 sitePortugal
- Study dates
- Mar 2026to Jul 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Aged 18 years or older.
- Physically active (engaging in regular physical activity at least 3 times per week - minimum of 180 min of physical activity).
Who cannot join
- Any musculoskeletal injuries at the time of data collection.
- Any medical condition that could compromise physical performance or safety during testing.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Portugal1 site
University of Maia
Maia, Porto District, 4475-690 Maia
Henrique S Sousa, MSc, +351 22 986 6000, hsousa.dcd@umaia.pt
About this study
Official title: Which Index Tells the Full Story? Comparing Reactive Strength and Dynamic Rebound Index in Drop Jump Performance
The stretch-shortening cycle (SSC) is a fundamental mechanism in explosive human movement, enabling musculotendinous units to store and release elastic energy, thereby allowing the body to produce higher forces and velocities with greater mechanical efficiency. Movements such as sprinting, jumping, hopping, and sudden changes of direction, which depend on rapid force application, are supported by an effective SSC. Because of this, identifying a simple and interpretable index of SSC function has long been a priority in both research and applied sport settings.
The Reactive Strength Index (RSI), most commonly defined as the ratio of jump height to ground contact time, has become the most widely used metric for quantifying SSC performance. However, this ratio presents notable methodological limitations: it combines variables of incompatible dimensions and is insensitive to drop height, thereby ignoring the eccentric load imposed on the musculotendinous system. The Dynamic Rebound Index (DRI), recently proposed as a dimensionless and mechanically grounded alternative, is calculated as DRI = (box height + jump height) / (9.8 × ground contact time²). Despite its theoretical advantages, a direct comparison between the RSI and DRI remains unexplored in the literature, which justifies the relevance of the present study.
This study aims to compare the RSI and the DRI in physically active adults of both sexes during the execution of the Drop Jump at four different drop heights (20, 30, 40, and 50 cm). The specific objectives are: (a) to characterize performance across the four height conditions; (b) to analyze differences between sexes in both indices; (c) to examine the effect of drop height on both indices; and (d) to explore the informative complementarity between the two indices.
- Conditions
- Physical Performance Parameters
- Being tested
- Drop Jump Protocol
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Drop Jump ProtocolOther
Also called DJ
Participants perform 3 valid Drop Jump trials at each of four drop heights (20, 30, 40, and 50 cm) in a randomized order, with 1 minute of rest between trials and 5 minutes between conditions. Jump height and ground contact time are recorded using a contact mat (ChronoJump, Boscosystem, Spain) for subsequent calculation of the RSI and DRI.
| Study group | Role | What they receive |
|---|---|---|
| Drop Jump 20 cm | Experimental | Participants perform 3 valid Drop Jump trials from a 20 cm drop height Receives: Other: Drop Jump Protocol |
| Drop Jump 30 cm | Experimental | Participants perform 3 valid Drop Jump trials from a 30 cm drop height Receives: Other: Drop Jump Protocol |
| Drop Jump 40 cm | Experimental | Participants perform 3 valid Drop Jump trials from a 40 cm drop height Receives: Other: Drop Jump Protocol |
| Drop Jump 50 cm | Experimental | Participants perform 3 valid Drop Jump trials from a 50 cm drop height Receives: Other: Drop Jump Protocol |
What is being measured
The primary outcome is the main question the study is designed to answer.
Reactive Strength Index (RSI)
Calculated as RSI = jump height (m) / ground contact time (s), measured during the Drop Jump at four drop heights (20, 30, 40, and 50 cm).
Measured: Baseline
Dynamic Rebound Index (DRI)
Calculated as DRI = (box height (m) + jump height (m)) / (9.8 × ground contact time² (s)), measured during the Drop Jump at four drop heights (20, 30, 40, and 50 cm)
Measured: Baseline
Secondary outcomes (2)
Jump Height
Vertical jump height (m) recorded via contact mat during the Drop Jump.
Measured: Baseline
Ground Contact Time
Time (s) spent in contact with the ground during the Drop Jump, recorded via contact mat.
Measured: Baseline
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Mar 2026
- Study startMar 2026 (estimated)
- Primary completionJul 2026 (estimated)
- Study completionJul 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Physical Performance ParametersStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- All participants will perform Drop Jump trials at four drop heights (20, 30, 40, and 50 cm) in a randomized order within a single experimental session.
- Masking
- None (open label)
- Enrolment
- 50 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University Institute of Maia
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Henrique Sousa, University Institute of Maia
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07475078
- Sponsor's protocol ID
- DRI_HS_01
- Status last verified
- Mar 2026
- First submitted
- 10 Mar 2026
- Last updated
- 16 Mar 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 16 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Which Index Tells the Full Story? Comparing Reactive Strength and Dynamic Rebound Index in Drop Jump Performance
- ClinicalTrials.gov ID
- NCT07475078
- Acronym / sponsor ID
- DRI_HS_01
- Conditions
- Physical Performance Parameters
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 50 participants (estimated)
- Lead sponsor
- University Institute of MaiaUniversity, hospital or other
- Study start
- Mar 2026 (estimated)
- Primary completion
- Jul 2026 (estimated)
- Study completion
- Jul 2026 (estimated)
- First posted
- 16 Mar 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The stretch-shortening cycle (SSC) is a fundamental mechanism in explosive human movement, enabling musculotendinous units to store and release elastic energy, thereby allowing the body to produce higher forces and velocities with greater mechanical efficiency. Movements such as sprinting, jumping, hopping, and sudden changes of direction, which depend on rapid force application, are supported by an effective SSC. Because of this, identifying a simple and interpretable index of SSC function has long been a priority in both research and applied sport settings.
The Reactive Strength Index (RSI), most commonly defined as the ratio of jump height to ground contact time, has become the most widely used metric for quantifying SSC performance. However, this ratio presents notable methodological limitations: it combines variables of incompatible dimensions and is insensitive to drop height, thereby ignoring the eccentric load imposed on the musculotendinous system. The Dynamic Rebound Index (DRI), recently proposed as a dimensionless and mechanically grounded alternative, is calculated as DRI = (box height + jump height) / (9.8 × ground contact time²). Despite its theoretical advantages, a direct comparison between the RSI and DRI remains unexplored in the literature, which justifies the relevance of the present study.
This study aims to compare the RSI and the DRI in physically active adults of both sexes during the execution of the Drop Jump at four different drop heights (20, 30, 40, and 50 cm). The specific objectives are: (a) to characterize performance across the four height conditions; (b) to analyze differences between sexes in both indices; (c) to examine the effect of drop height on both indices; and (d) to explore the informative complementarity between the two indices.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 4
- Model description
- All participants will perform Drop Jump trials at four drop heights (20, 30, 40, and 50 cm) in a randomized order within a single experimental session.
| Arm | Type | Receives |
|---|---|---|
| Drop Jump 20 cm | Experimental | Other: Drop Jump ProtocolParticipants perform 3 valid Drop Jump trials from a 20 cm drop height |
| Drop Jump 30 cm | Experimental | Other: Drop Jump ProtocolParticipants perform 3 valid Drop Jump trials from a 30 cm drop height |
| Drop Jump 40 cm | Experimental | Other: Drop Jump ProtocolParticipants perform 3 valid Drop Jump trials from a 40 cm drop height |
| Drop Jump 50 cm | Experimental | Other: Drop Jump ProtocolParticipants perform 3 valid Drop Jump trials from a 50 cm drop height |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (2 listed)
- Aged 18 years or older.
- Physically active (engaging in regular physical activity at least 3 times per week - minimum of 180 min of physical activity).
Key exclusion criteria (2 listed)
- Any musculoskeletal injuries at the time of data collection.
- Any medical condition that could compromise physical performance or safety during testing.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Drop Jump ProtocolAlso: DJParticipants perform 3 valid Drop Jump trials at each of four drop heights (20, 30, 40, and 50 cm) in a randomized order, with 1 minute of rest between trials and 5 minutes between conditions. Jump height and ground contact time are recorded using a contact mat (ChronoJump, Boscosystem, Spain) for subsequent calculation of the RSI and DRI. | Other | Drop Jump 20 cm, Drop Jump 30 cm, Drop Jump 40 cm, Drop Jump 50 cm |
Primary outcome
Reactive Strength Index (RSI)
Time frame: Baseline
Calculated as RSI = jump height (m) / ground contact time (s), measured during the Drop Jump at four drop heights (20, 30, 40, and 50 cm).
Dynamic Rebound Index (DRI)
Time frame: Baseline
Calculated as DRI = (box height (m) + jump height (m)) / (9.8 × ground contact time² (s)), measured during the Drop Jump at four drop heights (20, 30, 40, and 50 cm)
2 secondary outcomes
Jump Height
Time frame: Baseline
Ground Contact Time
Time frame: Baseline
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 16 Mar 2026.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Drop Jump Protocol in people with Physical Performance Parameters, run by University Institute of Maia at 1 site in Portugal.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 16 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Portugal. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Each site lists its own contact: choose the nearest one under Trial locations. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Reactive Strength Index (RSI) (time frame: Baseline). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 16 Mar 2026.