Performance Testing Protocol · SCI-PT-001
Isometric Mid-Thigh Pull
Force-Time Profiling Protocol
A maximal isometric lower-body multi-joint test performed on a force plate — what each metric reflects, which metrics are reliable enough to use, and how to apply the data in performance monitoring and return-to-sport contexts.
Overview
The isometric mid-thigh pull (IMTP) is a maximal isometric lower-body multi-joint test performed on a force plate with a fixed barbell set at mid-thigh height. The athlete attempts to produce maximum vertical ground reaction force as rapidly as possible by driving the feet into the ground against an immovable bar — without any joint movement occurring.
Unlike dynamic strength tests such as the 1RM back squat or power clean, the IMTP imposes minimal neuromuscular fatigue, requires little technical learning time, can be completed in a single brief session, and generates a multi-variable force-time curve from a single effort. A 2022 scoping review identified 48 publications examining the relationship between IMTP variables and dynamic sport performance assessments, with 89.6% of all comparisons reaching statistical significance.2
Reliability
Grgic et al. conducted a systematic review of 16 studies examining test-retest reliability of peak force in the IMTP, rating all 16 studies good-to-excellent using the COSMIN checklist.1 Peak force is the most reliable IMTP metric — instantaneous RFD and time to peak force are consistently unreliable and should not be used as primary outcomes.
| Metric | ICC Range | Median ICC | Median CV | ICC ≥ 0.90 |
|---|---|---|---|---|
| Absolute Peak Force | 0.84–0.99 | 0.97 | 4.6% | 88% |
| Relative Peak Force | 0.73–0.94 | 0.88 | 5.7% | 38% |
| Bilateral IMTP (all) | 0.73–0.99 | 0.96 | 5.3% | 75% |
| Unilateral IMTP | 0.89–0.97 | 0.94 | 4.1% | 88% |
ICC ≥ 0.90 = excellent relative reliability; CV ≤ 10% = acceptable absolute reliability.
| Metric | CV (%) | ICC | Reliable? |
|---|---|---|---|
| Peak Vertical Force (N) | 3.5 | 0.99 | ✓ Yes |
| Net Peak Force (N) | 7.1 | 0.94 | ✓ Yes |
| Force @ 200 ms (N) | 9.5 | 0.92 | ✓ Yes |
| Force @ 100 ms (N) | 9.9 | 0.84 | ✓ Yes |
| Force @ 50 ms (N) | 7.1 | 0.72 | ⚠ Caution (ICC < 0.80) |
| Absolute Impulse 0–200 ms | 8.5 | 0.87 | ✓ Yes — preferred early-phase metric |
| All RFD measures | >15 | <0.70 | ✗ Not reliable |
| Time to peak force | Very high | <0.70 | ✗ Not reliable |
Key implication: absolute impulse and instantaneous forces at 100–200 ms demonstrate utility for monitoring rapid force production. RFD measures are consistently unreliable and should be used with considerable caution.
Peak force reliability is high across youth populations (ICC: 0.72–0.99; CV: 2.0–8.3%), but early-phase force outputs at 50 ms and 100 ms show substantially greater variability (CV: 5.5–23.3%).6 In post-fatigue conditions (immediately after maximal CPET), IMTP reliability remains high (ICC = 0.93–0.98), supporting its use for neuromuscular fatigue monitoring.19
Protocol & Setup
Correct body position is the most critical standardization variable. The prescribed position mirrors the second pull of the power clean — near-upright trunk, knees partially flexed, bar at mid-thigh. Have the athlete self-select their second pull position first, then adjust bar height to achieve the prescribed joint angles. Do not set bar height first.
| Parameter | Range / Standard | Notes |
|---|---|---|
| Knee angle | 125–145° | Self-selected within this range is best practice in applied settings |
| Hip angle | 140–150° | Produces 5–10° forward trunk lean; 145° reported as optimal for peak force and RFD |
| Trunk lean | 5–10° forward | Shoulders directly above or slightly behind the bar; avoid excessive forward lean |
| Foot width | Approximately hip-width | Mark foot position on plates at each session; standardize across sessions |
| Bar contact | Against anterior mid-thigh | Bar rests against thighs, not hands; arms fully extended |
| Arm position | Fully extended | Elbows locked; no elbow flexion during the pull |
| Phase | Activity | Intensity | Duration | Rest |
|---|---|---|---|---|
| General | Bodyweight squats, lunges, hip hinges, CMJ | Low | 5–10 min | — |
| Submaximal 1 | Mid-thigh pull | 50% perceived max | 3 sec | 60 sec |
| Submaximal 2 | Mid-thigh pull | 75% perceived max | 3 sec | 60 sec |
| Submaximal 3 | Mid-thigh pull | 90% perceived max | 3 sec | 60–90 sec |
| Maximal trials | Full IMTP | 100% maximal effort | 2–5 sec each | 2–3 min between |
Collect minimum 3 maximal trials. Use the best single trial as the primary outcome — not the mean. If the final trial exceeds the prior best by ≥ 250 N, perform an additional trial until peak output plateaus. Rest 2–3 minutes between all maximal efforts.
Reject and repeat if any of the following are observed:
- Countermovement — downward loading spike visible on force trace before pull onset
- Unstable baseline during quiet period — force variance > 50 N from bodyweight
- Peak force achieved only at the very end of the effort window — indicates "yank" technique
- Feet lift, slide, or shift position during the pull
- Trunk extends excessively — athlete leans back into the pull
Cueing Strategy
Verbal cueing strategy has a direct impact on the quality of force-time data. Research and expert consensus consistently support external focus push cues — directing attention to the ground — rather than internal focus pull cues. Athletes cued to "pull" tend to hyperextend the lumbar spine and lean into trunk extension, changing the musculature being assessed and reducing measurement validity.
| Recommended — External / Push Focus | Not Recommended — Internal / Pull Focus |
|---|---|
| "Push your feet into the ground as fast and as hard as possible" | "Pull the bar up as hard as you can" |
| "Drive through the floor" | "Lift the bar" |
| "Maximum force, maximum speed — go" | "Pull as hard as you can" |
- "Step onto the force plates with your thighs touching the bar."
- "Grip the bar — do NOT create any tension yet."
- "Shoulders back, chest up, look straight ahead."
- Quiet period: 1–2 seconds of still standing — confirm force trace is stable at bodyweight before counting
- "Ready... 3... 2... 1... PUSH!" — Hold the effort for 2–5 seconds
- "Stay completely still on the plates until the trial is saved."
An audible start signal (three short countdown beeps followed by one sustained beep) is recommended to reduce reaction time variability across trials and sessions.
Force-Time Metrics
The IMTP produces a force-time curve from which multiple metrics can be derived. Understanding what each metric reflects — and which are sufficiently reliable for clinical and performance monitoring — is essential to accurate interpretation.
| Priority | Metric | What It Reflects | Reliability | Practical Use |
|---|---|---|---|---|
| 1st | Peak Force / Net Peak Force | Maximum isometric force capacity; NPF removes body mass differences | Excellent (ICC 0.97) | Primary outcome; baseline and longitudinal tracking |
| 2nd | Relative PF (N/kg or ×BW) | Strength relative to body mass; allometric scaling improves comparability | Good (ICC 0.88) | Cross-athlete and cross-sport comparison; benchmarking |
| 3rd | Absolute Impulse (0–100/200 ms) | Integrated area under force-time curve in a time window; most stable early-phase metric | Best of early-phase metrics | Preferred over RFD for comparing across sessions or devices |
| 4th | Force @ 100–200 ms | Force produced within specific time windows; reflects explosive strength capacity | Good at 100–200 ms; caution at 50 ms | Rapid force assessment; sprint and jump correlation |
| 5th | Dynamic Strength Index (DSI) | CMJ peak force ÷ IMTP peak force; ballistic vs maximal strength balance | Derived metric | Training needs classification (see DSI section) |
| ⚠ Caution | Instantaneous RFD / Time to peak force | Speed of force application | Poor (ICC < 0.70 consistently) | Use only epoch RFD (0–200 ms); avoid instantaneous RFD |
Comfort et al. demonstrated very large to nearly perfect correlations between IMTP peak force and force at 150 ms (r = 0.77), 200 ms (r = 0.88), and 250 ms (r = 0.94).9 When males and females were strength-matched on relative peak force, no meaningful sex differences in rapid force production at 150–250 ms were observed. Developing maximal isometric strength is the primary mechanism through which rapid force production is enhanced — RFD-specific training effects are secondary to increases in peak force capacity.
Dynamic Strength Index
The Dynamic Strength Index (DSI) is the ratio of CMJ peak force to IMTP peak force. It identifies whether an athlete's primary performance limitation is maximal strength or ballistic/explosive capacity, directing training prescription at the individual level.7
An athlete recovering from injury with suppressed CMJ output will show artificially low DSI independent of true training status. Longitudinal within-athlete tracking is more informative than cross-sectional comparison during rehabilitation. Do not classify a post-injury athlete as "ballistic deficient" based on acute DSI without accounting for injury-related CMJ suppression.
Performance Relationships
Giles et al. conducted a PRISMA-ScR scoping review of 48 publications examining the relationship between IMTP performance and dynamic sport performance assessments.2 89.6% of all comparisons across 48 studies reached statistical significance.
| Dynamic Measure | Studies | % Significant | Moderate (r = 0.41–0.70) | Strong (r ≥ 0.71) |
|---|---|---|---|---|
| Jump Height (CMJ/SJ) | 33 | 90.9% | 17 | 11 |
| Rate of Force Development | 32 | 96.9% | 16 | 13 |
| Peak Power | 22 | 100% | 17 | 3 |
| Sprint Speed | 13 | 92.3% | 8 | 3 |
| Change of Direction | 10 | 90.0% | 7 | 2 |
| Dynamic Strength (1RM, 3RM) | 12 | 100% | 6 | 5 |
| Sport-Specific Tasks | 17 | 94.1% | 10 | 6 |
Strong correlation defined as r ≥ 0.71. IMTP force-time variables explained r² = 0.12 to 0.94 of the variance in lower-body dynamic performance across included studies.4
Palmer et al. identified the IMTP as a practical and effective external performance monitoring tool in elite youth basketball (n = 14), with the combination of CMJ and IMTP representing a time-efficient weekly neuromuscular assessment battery.20 Direct basketball-specific IMTP normative databases remain limited in the published literature — use relative PF targets alongside individual athlete baselines and longitudinal tracking rather than population-level thresholds until basketball-specific databases are established.
Normative Data & Benchmarks
| Competitive Level | Absolute PF Range (N) | Notes |
|---|---|---|
| Youth / Developmental | 1,162–2,374 N | Substantial variability driven by maturation and training age |
| Academy / College | 1,855–3,104 N | Primarily rugby data; generalizable to team sport athletes of similar size |
| Professional / Elite | 2,254–3,851 N | Over 1,900 N range between lowest and highest elite means — large between-study variability |
| Threshold | Interpretation | Source |
|---|---|---|
| ≥ 2.5 × bodyweight | Commonly cited threshold for trained athletes in applied settings | Applied practice consensus |
| ≥ 3.0 × bodyweight | Elite-level isometric force production | Applied benchmark (Driveline Baseball context) |
| Net PF > 3,000 N | Absolute benchmark used in performance contexts as minimum strength criterion | Applied practice |
These benchmarks derive from applied practice rather than basketball-specific normative studies. Use alongside individual baselines and longitudinal tracking — not as standalone population thresholds.
When females and males are matched on relative peak force, sex differences in rapid force production at 150–250 ms disappear entirely.9 Absolute sex differences in IMTP output are a function of body mass differences, not neuromuscular sex effects. Relative force is the appropriate scaling variable when comparing across sex in team sport environments.
Rehabilitation Application
Stofberg et al. conducted the most directly applicable study of IMTP use in ACLR rehabilitation, assessing bilateral and unilateral IMTP at weeks 12, 16, and 20 in 15 ACLR patients alongside a healthy control cohort (n = 63).5
| Metric | Test Modality | Change (wk 12 → wk 20) | Rate |
|---|---|---|---|
| Peak force, injured limb | Bilateral IMTP | +0.94 N/kg | 0.1 BW/wk |
| Peak force, uninjured limb | Bilateral IMTP | +0.26 N/kg | — |
| Peak force, injured limb | Unilateral IMTP | +1.5 N/kg | 0.2 BW/wk |
| Asymmetry reduction | Bilateral IMTP | ~1% reduction | — |
| Asymmetry reduction | Unilateral IMTP | ~0.5% reduction | — |
Significant differences between ACLR group's injured limb and healthy controls persisted across all phases (p = 0.001–0.022). Estimated time to reach healthy control thresholds at observed progression rate: approximately 28 weeks.
The bilateral IMTP may fail to detect limb-specific force deficits in ACLR populations. Unilateral IMTP demonstrated greater sensitivity to injured limb changes (+1.5 N/kg vs +0.94 N/kg) and stronger correlation with isokinetic asymmetry (r = 0.45 vs r = 0.12 for bilateral).5 Use bilateral IMTP for global force monitoring and unilateral IMTP for limb-specific deficit tracking throughout rehabilitation.
- Implement bilateral and unilateral IMTP from week 12 post-ACLR forward
- Track limb symmetry index (injured ÷ uninjured × 100) using unilateral IMTP as the primary asymmetry metric
- Expected progression rate: approximately 0.2 BW per week in unilateral IMTP peak force during late-phase rehabilitation
- Do not use IMTP in isolation as a return-to-sport clearance criterion — combine with CMJ, single-leg hop testing, and isokinetic dynamometry
- Bilateral IMTP will systematically underestimate limb-specific deficits — unilateral testing is required for accurate limb-by-limb monitoring
- Isokinetic dynamometry detected progressive quadriceps weakness in the uninjured limb not captured by the IMTP — these tools are complementary, not interchangeable
Equipment Validity
A growing body of research has examined whether portable and lower-cost alternatives to laboratory force plates can validly replicate IMTP data. The evidence supports selective use of alternative devices with important caveats.
| Device Type | PF Validity | RFD / Early Force | Key Finding |
|---|---|---|---|
| Portable force plates (ForceDecks, ForceIntellec) | Valid (< 5% difference) | Inconsistent | Good PF consistency; RFD inconsistency across devices — use impulse instead13 |
| Load cell / sensor-based (Smart Traction) | Valid (mean diff 1.69 N) | Valid (mean diff –5.27 N/s) | Acceptable PF and RFD validity vs force plate14 |
| Portable isometric dynamometer (PID) | Acceptable (1.27% difference) | Not valid | Force@100ms 229% overestimated; Force@200ms 39% overestimated15 |
| Functional electromechanical dynamometer (FEMD) | Valid for PF (r = 1.00) | Not reliable | PF acceptable; RFD and early force not reliable16 |
Practical rule: use impulse-based metrics (not RFD) when comparing data across portable devices or between different equipment across sessions. RFD inconsistency across devices is a major threat to longitudinal validity.
Key Takeaways
- Peak force is the primary outcome. Absolute peak force has excellent reliability (ICC = 0.97, CV = 4.6%). Net peak force is preferred for cross-athlete comparison. RFD measures are consistently unreliable and should not be used as primary outcomes.1,3
- Use absolute impulse, not instantaneous RFD, for early-phase force profiling. Impulse at 0–200 ms is the most reliable early-phase metric and is preferred when comparing across sessions or devices.3
- External push cues produce better data than internal pull cues. "Push your feet into the floor" elicits correct mechanics; "pull the bar" encourages lumbar hyperextension and invalidates the measurement.
- Maximal strength drives rapid force production. Peak force explains 59–89% of the variance in force at 150–250 ms. Developing maximal strength is the primary mechanism for improving explosive capacity.9
- DSI directs training prescription. DSI < 0.60 = ballistic priority; DSI 0.60–0.80 = concurrent; DSI > 0.80 = strength priority. Do not use DSI in isolation during rehabilitation.7
- Bilateral IMTP underestimates limb-specific deficits in ACLR. Unilateral IMTP is required for accurate limb-by-limb monitoring. Expected late-phase rehab progression: ~0.2 BW/week in unilateral peak force.5
- IMTP is a monitoring tool, not a clearance criterion. It must be combined with CMJ, single-leg hop testing, and isokinetic dynamometry for return-to-sport decisions.5
The IMTP earns its place in any applied sport science battery because it satisfies a rare combination of demands: high reliability, minimal fatigue, short testing time, and a force-time curve that correlates significantly with nearly every dimension of dynamic athletic performance. Used correctly — with standardized position, external push cues, best-trial scoring, and absolute impulse as the preferred early-phase metric — it is one of the most information-dense tests available to clinicians and performance staff.
Its limitations are also clear: RFD measures are unreliable, bilateral testing masks limb asymmetry in injured populations, and it cannot be used as a standalone return-to-sport criterion. Within a battery that includes CMJ, single-leg hop testing, and isokinetic dynamometry, the IMTP fills a specific role — maximal isometric force profiling and DSI-guided training prescription — that no other single test replicates as cleanly.
- Grgic J, Scapec B, Mikulic P, Pedisic Z. Test-retest reliability of isometric mid-thigh pull maximum strength assessment: a systematic review. Biol Sport. 2022;39(1):3-11.
- Giles G, Lutton G, Martin J. Scoping review of the isometric mid-thigh pull performance relationship to dynamic sport performance assessments. J Funct Morphol Kinesiol. 2022;7(4):114.
- Merrigan JJ, Stone JD, Hornsby WG, Hagen JA. Identifying reliable and relatable force-time metrics in athletes: considerations for the IMTP and CMJ. Sports. 2021;9(1):4.
- Lum D, Haff GG, Barbosa TM. The relationship between isometric force-time characteristics and dynamic performance: a systematic review. Sports. 2020;8(5):63.
- Stofberg JPJ, Aginsky K, van Aswegen M, Kramer M. Changes in IMTP peak force and symmetry across ACLR rehabilitation phases. Front Rehabil Sci. 2024;5:1418270.
- Bruno J, Montoro-Bombu R, Thapa R, Sarmento H. Reliability of IMTP for maximal strength testing in youth athletes: a systematic review. Int J Sports Sci Coach. 2025.
- Thomas CM, Dos'Santos T, Jones PA. A comparison of dynamic strength index between team-sport athletes. Sports. 2017;5(3):71.
- Thomas C, McMahon J, Comfort P, Jones PA, Dos'Santos T. Relationships between isometric force-time characteristics and dynamic performance. Sports. 2017;5(3):68.
- Comfort P, McMahon J, Lake JP, Ripley N, Triplett NT, Haff GG. Relative strength explains differences in multi-joint rapid force production between sexes. PLoS ONE. 2024;19(2):e0296877.
- Martin E, Beckham GK. Isometric mid-thigh pull performance in rugby players: a systematic literature review. J Funct Morphol Kinesiol. 2020;5(4):91.
- Keogh C, Collins DJ, Warrington G, Comyns T. Intra-trial reliability of IMTP testing on portable force plates. J Hum Kinet. 2020;71:241-252.
- Moeskops S, Oliver JL, Read PJ, et al. Within- and between-session reliability of the isometric midthigh pull in young female athletes. J Strength Cond Res. 2018;32(7):1892-1901.
- Wang H, Guo X, Shi Q, Zhang K, Shen Y. Concurrent validity of a portable force plate system for measuring IMTP. J Sports Sci. 2025.
- Montoro-Bombu R, Gomes B, Santos A, Rama L. Validity and reliability of a load cell sensor-based device for IMTP assessment. Sensors. 2023;23(13):5832.
- Lum D, James LP, Stutter LR, Talpey S. Reliability and validity of IMTP measures from a portable isometric dynamometer. Int J Strength Cond. 2025;5(1).
- Baena-Raya A, Diez-Fernandez DM, Garcia-Ramos A, et al. Concurrent validity and reliability of a functional electromechanical dynamometer for IMTP. Proc Inst Mech Eng P. 2021.
- Drake D, Wallace E, Kennedy R. The validity and responsiveness of isometric lower body multi-joint tests: a systematic review. Sports Med Open. 2017;3:23.
- Grover Z, McCormack J, Cooper J, Fisher J. Test-retest reliability of a single IMTP protocol for peak force and strength-endurance. PeerJ. 2024;12:e17951.
- Pojskic H, Schiller J, Pagels P, Ragnarsson T, Melin A. Are CMJ and IMTP reliable when performed after maximal CPET? Front Physiol. 2025;16:1663590.
- Palmer BL, van der Ploeg G, Bourdon P, Butler S, Crowther R. Evaluation of athlete monitoring tools across 10 weeks of elite youth basketball training. Sports. 2023;11(2):26.