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Strength exercise is an active and dynamic activity that involves applying force against a resistance. This produces fatigue, seen as a reduced ability to apply force during and after the exercise, and perceived effort, which is a person's subjective feeling of how hard they are working.
Strength exercise can also be used for therapy, as it has many benefits for different parts of the body. One of these is changing how the individual feels pain. It has been shown that doing strength exercises can reduce pain perception, a phenomenon called exercise-induced hypoalgesia (EIH), although the exact physical reasons and the amount of exercise needed to cause this effect are not yet known.
One of the most studied exercises in this area is the leg extension machine. This is a specific exercise where the legs move freely (open kinetic chain) and the machine guides the movement, which helps keep things stable and limits the effect of other factors. It is usually used to strengthen and grow the muscles in the front of the thigh, especially the quadriceps, but it can also be used to study the effects on EIH.
The main goal of this study is to see if fatigue and perceived effort during strength exercise are important for EIH to happen in healthy people. Participants will complete 3 sessions, at least 7 days apart. These will include a control session and 2 sessions designed to show different levels of fatigue. Before, during, and after the sessions, the investigators will measure pain sensitivity, isometric strength, and perceived effort. Also, there will be a test to find the maximum weight for 10 repetitions and several questionnaires to collect basic info (sex, age, height...), weekly physical activity, experience with strength training, and other factors like sleep quality, stress, and mood. All this information will be completely anonymous when the study results are shared.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Control | Sham Comparator |
| |
| Low fatigue | Experimental |
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| High fatigue | Experimental |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Seated leg extension machine: low fatigue | Behavioral | Seated leg extension machine using 10RM external load for 6 sets of 5 repetitions with180 seconds rest between sets and a cadence of 1:2 second concentric:eccentric |
| Measure | Description | Time Frame |
|---|---|---|
| Pain pressure threshold | Pain pressure threshold measured with an analogic algometer (Baseline Dolorimeter, MVS In Motion SL, Belgium), in kilograms. These measurements will be taken at a local level (on one of the thighs, over the rectus femoris of the quadriceps, at the midpoint between the pelvic surface and the patella) and at a distance (on the neck over the belly of one of the upper trapezius muscles, at the midpoint between the surface of C7 and the acromion). The pressure will be applied at a rate of 1kg/s and the patient will be instructed to notify the first instance of pain. | Baseline, immediately post-exercise, 30 minutes after exercise |
| Pressure-evoked pain | Pain evoked by a 6kg pressure exerted with an analogic algometer (Baseline Dolorimeter, MVS In Motion SL, Belgium), at a rate of 1kg/s, measured with a numeric rating scale where zero is equivalent to no pain and 10 indicates the worst possible pain. These measurements will be taken at a local level (on one of the thighs, over the rectus femoris of the quadriceps, at the midpoint between the pelvic surface and the patella) and at a distance (on the neck over the belly of one of the upper trapezius muscles, at the midpoint between the surface of C7 and the acromion). | Baseline, immediately post-exercise, 30 minutes after exercise |
| RPE (Rating of Perceived Exertion) | Perceived exertion was measured on OMNI-Resistance exercise Scale where 0 is equivalent to no effort and 10 indicates maximal exertion. | Immediately after each set of the training session |
| sRPE (Session rating of perceived exertion) | Session Perceived Exertion was measured on a scale where 0 is equivalent to no effort and 10 indicates maximal exertion. | Monitoring will take place 30 minutes after the final set, ensuring that the exertion from the last set does not interfere with the overall session RPE. |
| Measure | Description | Time Frame |
|---|---|---|
| Kinematic measures | Angular position (º), velocity(º/s) and acceleration(º/s^2) of the machine's pad during the exercise will be recorded using an accelerometer (BWT901CL, WitMotion Shenzhen Co., Ltd). | During each set of the exercise intervention in all 3 sessions (3 or 6 sets depending on each arm). Total measurement time approximately 3 minutes during a single experimental session (as the device will stop recording during rest periods between sets). |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Miguel Delicado Miralles, Physiotherapy | Contact | +34 679788377 | mdelicado@umh.es |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Universidad Miguel Hernández | Alicante | ALICANTE | 03550 | Spain |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 39590221 | Background | Hogge R, Mascheri M, Shurik D, Hanney WJ, Anderson AW. High-Fatigue Dynamic Resistance Exercise Induces Significant Hypoalgesia Effect. J Strength Cond Res. 2025 Feb 1;39(2):165-172. doi: 10.1519/JSC.0000000000004985. Epub 2024 Nov 26. | |
| 33062901 | Background | Vaegter HB, Jones MD. Exercise-induced hypoalgesia after acute and regular exercise: experimental and clinical manifestations and possible mechanisms in individuals with and without pain. Pain Rep. 2020 Sep 23;5(5):e823. doi: 10.1097/PR9.0000000000000823. eCollection 2020 Sep-Oct. |
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| Type | Includes Protocol | Includes SAP | Includes ICF | Document Label | Document Date | Document Uploaded Date | Document File Name |
|---|---|---|---|---|---|---|---|
| Prot_SAP_ICF | Yes | Yes | Yes | Study Protocol, Statistical Analysis Plan, and Informed Consent Form | Mar 27, 2025 |
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Double-blind randomized crossover controlled trial
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The Statistician will also be masked
| Seated leg extension machine: high fatigue | Behavioral | Seated leg extension machine using 10RM external load for 3 sets of 10 repetitions with 180 seconds rest between sets and a cadence of 1:2 second concentric:eccentric |
|
| Seated leg extension: control | Behavioral | Seated leg extension machine using no external load for 6 sets of 5 repetitions with 180 seconds rest between sets and a cadence of 1:2 second concentric:eccentric |
|
| Repetitions in Reserve (RIR) |
Using the ERF (Estimated Repetitions to Failure) scale where 0 is equivalent to maximal effort or muscular failure, and higher numbers indicate lower effort. For this purpose, subjects will be asked how many more repetitions they believe they could have performed after each set. |
| Immediately after each set of the training session. |
| Muscle fatigue | This will be monitored taking into account objective variables (not dependent on the patient's subjective report), through isometric knee extension action tests measured by dynamometry using a portable load cell (Model 620 Tedea-Huntleigh, Vishay Precision Group Inc., Holon, Israel) and Chronojump software (Chronojump Bosco System, Barcelona, Spain). The variables used are the maximal voluntary isometric contraction (MVIC) measured in Newtons (N) and the Rate of Force Development (RFD) which calculates the slope of the force-time curve. | Baseline, immediately post-exercise, 30 minutes after exercise |
| Wellness | Data regarding fatigue, sleep quality, DOMS, stress levels and mood will be tracked every session using a Wellness questionnaire where 5 is the best outcome and 1 is the worst for each individual item. | Prior to each exercise session. |
| Fitness level | The subject's level of physical activity will be collected via the IPAQ (International Physical Activity Questionnaire), which accounts for every physical activity performed throughout the week prior to taking the questionnare and converts them to METs (Metabolic Equivalent of a Task). Higher values indicate higher degree of fitness, and 0 being the floor (zero physical activity). | Baseline (Day 1) |
| 32599154 | Background | Wewege MA, Jones MD. Exercise-Induced Hypoalgesia in Healthy Individuals and People With Chronic Musculoskeletal Pain: A Systematic Review and Meta-Analysis. J Pain. 2021 Jan;22(1):21-31. doi: 10.1016/j.jpain.2020.04.003. Epub 2020 Jun 26. |
| Mar 15, 2026 |
| Prot_SAP_ICF_000.pdf |
| ID | Term |
|---|---|
| D005221 | Fatigue |
| D009043 | Motor Activity |
| ID | Term |
|---|---|
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
| D001519 | Behavior |
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