Measuring What Matters: How to Use Hawkin TruStrength Metrics in Rehab and Performance

Force diagnostics don't need to be complex — but they do need to be accurate, relevant, and practical. 

That’s the driving philosophy behind the Hawkin TruStrength Metrics Playbook, a newly released E-book designed to help clinicians, coaches, and researchers better understand the key metrics captured by the TruStrength system — and how to apply them across the continuum of rehabilitation and performance. 

The Training Pyramid: A Progressive Model for Strength Qualities 

The TruStrength framework is underpinned by a training pyramid (Figure 1) that progresses from foundational to advanced neuromuscular qualities: 

1. Strength Endurance 
2. Maximal Strength 
3. Explosive Strength 

Figure 1

This sequence is deliberate and evidence-based, mapping closely to both rehabilitation stages and periodized training models. Here's how each tier is defined, measured, and applied using TruStrength. 

Definition: 
Strength endurance is the ability of the neuromuscular system to produce force without fatiguing. Typically, this type of assessment and training involves low force/ intensity loading and is ideally suited for early season or early-stage rehab. The aim is to increase the intensity and/or volume over time and provide a solid foundation for the other strength qualities. 

Best suited for: 

• Early-stage rehabilitation 
• Off-season or base training phases 

HTS Metrics: 

• Mean force 
• Impulse 

Example Application: 

Let’s say you have an athlete recovering from ACL reconstruction and you have them perform an isometric knee extension at 100 N for 20 seconds. Over time, the goal may be to maintain the same force for longer durations (e.g., 30 seconds), or increase the mean force to 110 N over the same 20 second duration.  

Definition: 
Maximal strength is the highest amount of force produced during a movement or isometric action. Typically, this type of assessment and training involves high force loading and is ideally suited for mid-stage rehab. After you have built a solid foundation of strength endurance during early-stage rehab, you want to focus on increasing the force output of your client/athlete.  

Best suited for: 

• Mid-stage rehabilitation 

• Pre-season strength building 
• Monitoring readiness 

HTS Metrics: 

• Peak force (N) 

• Relative peak force (N/kg) 

Example Application: 

Tracking isometric strength may be a safe and time efficient way to monitor your athlete’s strength pre-season and during season, for example, you may have your field sport athlete perform an isometric mid-thigh pull (IMTP) and they produce a peak force of 1800 N. After a strength-focused training block, this increases to 2000 N. This way of tracking maximal strength is time efficient, portable and safe for the athlete.  

Definition: 
Explosive strength refers to how quickly your athlete or client can produce force during a given movement or isometric task. This type of assessment is ideally suited for late-stage and return-to-play (RTP) rehabilitation. After you have built a solid foundation of strength endurance during early-stage rehab and built up your maximal force production during mid-stage rehab, you want to focus on increasing the explosiveness of your client/athlete. 

Best suited for: 

• Late-stage rehabilitation 

• RTP decision-making 
• In-season performance monitoring 

HTS Metrics: 

• Peak rate of force development (RFD) 

• Explosive Strength Index (ESI) 
• Time to peak force (TTPF) 

Example Application: 

Let’s say you have an athlete who is nearing the end of their rehabilitation and wants to get cleared to RTP after a hamstring strain. Pre-injury, the athlete was producing peak forces of 500 N and peak RFD of 1540 N·s −1. In their RTP assessment, they are now producing peak forces of 495 N and peak RFD of 1000 N·s −1. Despite restored peak force, their peak RFD is still ~42% lower than their peak RFD numbers pre-injury, suggesting their neuromuscular system can produce high force, but not rapidly express it, which may influence your decision to clear them for RTP.  

Simplicity with Depth: Fewer Metrics, Greater Meaning 

The TruStrength system is designed to emphasize clarity and consistency by focusing on a small number of core metrics. This approach supports a better signal-to-noise ratio in your assessments, enabling users to concentrate on metrics that are both reliable and relevant across rehabilitation and performance settings. 

Key metrics include: 

• Peak force to assess maximal strength capacity 

• Mean force and impulse to evaluate strength endurance 
• Peak RFD, TTPF and ESI for explosive output 

These metrics are sampled at 1200 Hz, allowing for precise force-time analysis. By maintaining a focused set of outputs, TruStrength supports deeper insight into neuromuscular function and facilitates consistent tracking over time. 

Download the Full E-book 

The TruStrength Metrics Playbook is your comprehensive guide to measuring and applying strength data using the Hawkin TruStrength system.