Notes on Strength Testing, Strength Qualities, and Needs Analysis
Current testing modalities in resistance training and their limitations
Several approaches are commonly used to assess strength and performance: 1RM or 3RM tests for maximal strength; force plates enabling measures such as drop jumps and isometric mid-thigh pulls; wellness questionnaires (sleep, nutrition, training diary) to gauge recovery status; velocity-based training devices (e.g., Gym Aware, BarSense) to track movement velocity; VO2 max testing and timing gates for aerobic and sprint metrics. The lecturer notes that although there is a lot of information available from these tests, not all information is equally useful. The risk is information overload, with potentially hundreds of metrics per test; the challenge is deciding which metrics to keep, which to discard, and how to interpret them efficiently so that findings are actionable for athlete development and sport performance.
The needs-analysis framework and objective validity of tests
The discussion highlights a two-step, logic-driven approach: (1) perform an objective needs analysis to identify what the athlete must do in their sport, their current level and injury status, and (2) select assessments that capture information about these demands without overwhelming analysis routines. The aim is to extract measurements that are distinct across tests and representative of different strength domains. The process connects to foundational principles: test selection should be sport-specific, practically feasible, and interpretable, with the output clearly linked to performance goals. This aligns with the broader concept of ecological validity: the test should reflect real-world performance contexts and support decision-making about training emphasis.
Strength-quality taxonomy and the diagnostic framework
Two influential bodies of work guide the classification used in this course. The first approach segments strength into a spectrum of domains, including maximal strength and high-load speed strength (often described as power under heavier loads), low-load speed strength (power under light loads), rate of force development (RFD), reactive strength, and skill performance (the ability to execute movements effectively using the other qualities). The second framework (led by Australian researchers, with Lachlan James and Scott Telpe among others) emphasizes five distinct domains: fast strength, maximal isometric strength, explosive strength, slow strength, and reactive strength. The idea is that these domains have sufficiently low shared variance (low coefficient of variation across measures) to be considered distinct: for example, maximal isometric strength explains a portion of fast strength but not all of it, indicating meaningful independence between domains. The extent of shared variance is often summarized with R-squared values (R^2). For instance, maximal isometric strength explains about 40% of fast strength (R^2 ≈ 0.40), leaving about 60% unexplained by maximal strength and suggesting other contributing factors.
Quantitative relationships among strength qualities (shared variance and practical implications)
The analyses presented indicate varying degrees of overlap among the domains. For explosive strength, the shared variance with maximal strength is smaller at early time points (e.g., around 100 ms after initiation, R^2 ≈ 0.46), grows at later time points (e.g., 150 ms, R^2 ≈ 0.50), and becomes substantial at around 250 ms (R^2 ≈ 0.76). This pattern implies that very early explosive outputs (near 50–100 ms) are relatively distinct from maximal strength, while later outputs begin to blend with maximal strength. The practical takeaway is that different time windows on a force-time curve reflect different physical determinants and should be treated as separate, though related, constructs. Similar logic applies to other domains: fast strength, slow strength, and reactive strength all show varying degrees of independence from one another, justifying a multi-metric testing approach rather than collapsing everything into a single score.
Testing protocols by strength domain: overview and rationale
The lecture lays out how to test each domain, what the primary outcome should be, and how to interpret results in a way that informs training and performance.
Fast strength
What to test: Countermovement jump (CMJ) or squat jump (unloaded or light loads).
Key consideration: CMJ uses the stretch-shortening cycle (SSC) with an eccentric downward phase followed immediately by concentric propulsion, whereas a squat jump minimizes the eccentric portion.
Practical guidance: If you want to understand the contribution of the eccentric stretch, use CMJ; if you want a pure concentric output, use SJ. The force-time trace should be analyzed to identify appropriate metrics.
Representative metrics: Given a large set of potential variables (e.g., force at peak power, peak force, peak power, impulse, velocity measures, etc.), the data show that many metrics cluster and convey roughly the same information. The recommendation is to select a small, representative subset that captures distinct aspects of performance. For CMJ, common practical picks are peak force and rate of force development (RFD), or a timing metric (e.g., time to peak velocity). The aim is to summarize the explosive output with one or two interpretable metrics rather than dozens.
Interpretation: Early explosive outputs (e.g., around 100 ms) show substantial but not complete overlap with maximal strength; late outputs (e.g., around 250 ms) show higher overlap, indicating that the same lift may tap into both explosive and maximal strength components. Thus, measurement timing matters for interpretation and training emphasis.
Practical takeaway: In practice, use one clear metric (e.g., force at 100 ms or rate of force development) and, if needed, a second timing metric to convey how quickly the subject can generate force, to create a concise profile.
Explosive strength: time windows and metric choices
Time windows and shared variance: 50 ms (low shared variance and reliability issues due to measurement noise) → 100 ms (sweet spot with around R^2 ≈ 0.46 to maximal strength), 150 ms (≈ R^2 ≈ 0.50), 200–250 ms (R^2 grows to ≈ 0.6–0.76 with maximal strength). By ~250 ms, peak force tends to explain a large portion of the variance, sometimes enough that measuring additional variables yields diminishing returns.
Recommended metrics by window:
100 ms: force at a given time (e.g., F(100 ms)) is a reliable indicator of explosive strength with manageable reliability across days.
150–200 ms: impulse or rate of force development can be informative but should be used cautiously due to potential reliability concerns.
Overall: prefer a single clear metric such as force at a fixed time (e.g., 100 ms) or peak force, with a second metric only if you have a reliable protocol to capture it.
Practical implications: Explosive strength is faster than fast strength; it reflects the very early SSC mechanics and requires precise cueing and timing to capture consistently. The instructor emphasizes that correct interpretation hinges on using the appropriate time window and acknowledging that metrics beyond a certain point may begin to reflect maximal strength more than pure explosive capacity.
Maximal isometric strength
Test and setup: Isometric mid-thigh pull (IMTP) or isometric squat can be used; cues may involve a harness or a belt to unload the upper back and facilitate a strict push.
Criteria and interpretation: In the force trace, peak force is a primary indicator of maximum capability; the trace typically shows a rapid rise, plateau, then a drop. The peak force is considered the best direct indicator of true maximal strength.
Queuing and technique: The way tests are cued matters for the data: instruct athletes to push as hard and as fast as possible, or to ramp to a maximum over a set duration (e.g., “over 3 seconds, ramp to peak”). The cueing strategy affects rate of force development versus peak force and thus influences the interpretation of the test. The choice of cueing depends on whether you want to emphasize maximal strength or the quality of rapid force generation.
How to integrate with other measures: The maximal strength value often has ~40% shared variance with fast strength, indicating meaningful but partial overlap. The test is highly specific and can be paired with other measures (e.g., explosive strength and speed) to create a fuller profile.
Slow strength
Test and rationale: This domain is the traditional slow, grinding strength demonstrated in the main lift (often back squat or bench press) using 1RM or 3RM loads. Slow strength tests reflect the ability to sustain high force output under heavy loads, integrating technical skill and strength endurance.
Velocity considerations: Velocity-based training adds a layer by measuring the speed at which the bar moves at a given load. The velocity at 1RM/3RM can change even if the absolute 1RM does not, indicating adaptations that are not captured by a single maximal-lift score.
Practical implication: Slow strength is highly specific to the main lift and training should reflect that specificity. Gains in 1RM may occur alongside slower or faster bar speed, and these relationships can inform training prescription (e.g., velocity targets, autoregulation).
Reactive strength
Concept and context: Reactive strength reflects how well the neuromuscular system utilizes a rapid stretch-shortening cycle, particularly the fast SSC, in dynamic movements such as sprinting, jumping, and changing direction. It is distinct from the other domains and is often most relevant to explosive and sprint-oriented performance.
Tests and metrics: Reactive strength is most commonly assessed with drop jumps (DJ) and, in some protocols, counter movement jumps (CMJ) with a reactive-strength index (RSI). A common RSI is height divided by contact time: RSI = rac{H}{t_c}.
RSI and RSImod: RSImod (or MRSI) is calculated from a CMJ as height divided by time to take-off: RSI{mod} = rac{H}{t{takeoff}}. These metrics capture different aspects: DJ RSI emphasizes the very fast SSC (fast phase) while RSI_mod derives from a CMJ and tends to reflect a slower SSC component.
Interpretive nuance: The literature shows that RSI and RSImod measure related but distinct constructs. Correlations between RSI from a drop jump and RSImod from CMJ are moderate (e.g., R ≈ 0.5–0.7), and shared variance is limited (R^2 values around 0.2–0.5 depending on height and test). Importantly, a CMJ-based RSI_mod may be more sport-specific for activities with longer contact times, whereas DJ RSI targets the fastest SSC mechanics. Hence, practitioners may need to perform both tests or choose the test that best aligns with sport demands.
Test ranges and interpretation: The drop height affects RSI; there is an optimal height (often around 45–60 cm in the example) where RSI is maximized. Lower heights may underload the SSC; higher heights may exceed the athlete’s tolerance and reduce RSI. This underscores the need for event-specific testing and careful interpretation of RSI across heights.
Practical implication: RSI testing informs reactive-strength training, including plyometrics that emphasize rapid ground contact and high force in very short time windows. When using RSImod, be mindful that it captures a different aspect of reactive strength and may be more sensitive to slower SSC properties. In practice, some teams use RSI (DJ) to target fast SSC, and RSImod (CMJ-based) to reflect sport contexts with longer contact times. The approach you choose should be guided by needs analysis and sport specificity.
Practical testing framework: how to combine domains with a three-test approach
To cover all five strength domains efficiently, the curriculum proposes using three tests, typically:
A jump test (to capture fast and reactive strength components) – either CMJ or CMJ with DJ subset; the first metric should be height, velocity, or power, with a second metric capturing timing (e.g., time to peak velocity or contact time).
An IMTP or ISO strength test (for explosive strength and isometric/isolated explosive contributions) – first metric is force at a short latency (e.g., 50–100 ms), or RFD or impulse; a second metric could be a timing cue.
A main strength lift (slow strength) – e.g., back squat or bench press with a 1RM or 3RM; optionally include velocity data to gauge how bar speed changes as loads approach maximal effort.
The idea is to use a jump to capture fast and reactive qualities, an IMTP to capture explosive and isometric strength, and a main lift to capture slow strength. When combined, these three tests aim to span all five strength domains with three movements, ensuring practical feasibility while maintaining diagnostic breadth.
Training implications: mapping testing to training emphasis
Fast strength: often reflects performance in the early SSC; training should blend controlled heavy strength work (to build absolute force) with ballistic or plyometric work emphasizing the eccentric-to-concentric transition in a slow SSC context (to connect to fast outputs) and weightlifting derivatives for rapid force generation.
Explosive strength: focus on achieving rapid force production with a strong concentric component; cues emphasize fast initiation and short ground contact times. Training includes IMTP/ISO squat emphasis on rapid force development and early-time metrics, along with explosive movements that load the early phase of contraction.
Maximal isometric strength: prioritize true maximal force output with minimal eccentric involvement to avoid SSC contributions; CQ cues should promote maximum concentric drive without bouncy or pre-stretch effects.
Slow strength: target through main lifts at high loads with speed targets that may change across phases (velocity-based training can reveal when a lift’s speed changes as load increases), maintaining technique and gradual progression.
Reactive strength: emphasize rapid ground contact with low contact times using plyometrics that stress the fast SSC; adaptively select drills that reflect the sport’s preferred planes of motion (vertical vs lateral jumps) and include sport-specific context (e.g., directional plyometrics for changed direction agility).
Transfer to sport and context: training programs should reflect the athlete’s sport demands (CGS sports vs team sports). Tests should inform which domain to prioritize for a given athlete, guided by needs analysis, sport-specific performance factors, and evidence linking domains to meaningful performance outcomes (e.g., sprint speed, jump height, tackle effectiveness).
Needs analysis and decision-making for test selection in practice
The lecturer emphasizes several decision criteria for testing in practice:
Sport and position: event-specific demands (e.g., track vs basketball vs football) dictate which strength qualities matter most; some tests are more informative in certain contexts than others. For many team sports, multiple factors influence performance beyond pure strength.
Athlete level: professional, amateur, or developing athletes require different degrees of testing granularity; highly trained athletes may need more precise, sport-specific metrics, while beginners may benefit from simpler measures.
Training-responsive metrics: choose metrics that not only reflect current performance but can track meaningful changes with training and guide program adjustments.
Correlations with wins/losses: consider which metrics show stronger associations with actual performance outcomes in the sport (e.g., sprint speed with certain team-sport outcomes, bench-specific associations with physical contests in football).
Practicality and feasibility: minimize time and analysis burden; prefer metrics that can be computed easily from a standard test setup and interpreted without complex calculations.
Multimodal approach: because different strength domains contribute to performance in different ways, it is often necessary to perform more than one test or to use a multi-metric framework (e.g., CMJ for reactive and fast strength plus IMTP for explosive strength, plus a main lift for slow strength).
Case-by-case decisions: adapt testing to the athlete’s needs; for example, an athlete with strong baseline in most domains but weak reactive strength may benefit from targeted plyometrics and RSI-focused testing, whereas a different player might require emphasis on maximal or explosive strength depending on sport demands.
Summary of key practical takeaways for exam-ready understanding
Ecological validity and simplicity are critical: select a few representative metrics that explain performance and are feasible to analyze in practice.
Five-strength-domain framework (fast strength, maximal isometric strength, explosive strength, slow strength, reactive strength) captures distinct, partially independent facets of strength; to justify multiple tests, note nonzero shared variance values (e.g., maximal strength explains about 40% of fast strength; explosive strength shows time-dependent shared variance with maximal strength ranging from ≈0.46 at 100 ms to ≈0.76 at 250 ms).
Time windows matter: early outputs (e.g., 50–100 ms) capture explosive characteristics with lower overlap with maximal strength; later windows (150–250 ms) show increasing overlap, guiding metric selection.
Practical metric selection rules: for CMJ-based fast strength, pick one primary metric (e.g., force at 100 ms or peak force) plus a simple timing metric; for explosive strength, a reliable 50–100 ms metric (e.g., force at a fixed time) often provides a robust, interpretable indicator; for RSI-based reactive strength, RSI = height / contact time or RSI_mod = height / time to take off; and be mindful of test-tasks’ specificities and sport relevance.
RSI vs RSI_mod reflect different SSC regimes (fast vs slower components); outcomes should be interpreted in the context of sport demands and testing practicality; consider employing both if sport specificity warrants.
Three-test framework (jump, IMTP/ISO strength, main lift) can cover fast, explosive, and slow strength domains while remaining feasible; this aligns with a practical needs-analysis-driven approach to performance assessment.
Training integration: align training modalities with targeted strength domains, using heavy slow lifts for slow strength, weightlifting derivatives and dynamic effort for explosive/fast strength, plyometrics for reactive strength, and sport-specific drills to translate gains into performance.
Strategic decisions should balance causality and correlation: tests should inform training choices, while recognizing that performance is multifactorial and influenced by technique, conditioning, strategy, and sport context.
The overall aim is to deliver ecologically valid, interpretable insights that guide targeted training, justify testing choices in the needs analysis, and support decision-making that improves athlete performance across their sport context.