Rate of force development (RFD) is an inherently variable index and no matter the device or laboratory set-up, it is imperative to have a stable measurement environment and a familiarised participant. Producing explosive muscle contractions can require a bit of training for some.
Then you need to consider the device - does it have a high enough sampling (SF) frequency to give you accurate data? Here you’re looking for a minimum SF of 500Hz (See question below: What is the best sampling frequency?)

Absolutely! Well-conducted HHD tests with standardised and repeatable positions and protocols are a fantastic way to objectively track muscle performance over time - or between limbs.

Measurement error refers to the variability of a measurement. The greater the error, or variability the less confident we can be about the score representing the person’s true value, and the less we can rely on it to help make data-informed decisions. Error comes from technical and biological sources and it is important that the assessor addresses these sources of error.

 (See this blog and this research article on measurement error)

This is a really important question when we’re assessing individuals and trying to discern intra-individual change or difference - which represents most applications in clinical and coaching practice. When assessing individual performance it is wise to obtain a number of maximal trials and take the average (versus reporting the single max value). This dilutes measurement error and gets closer to real / true value. Take an average of 3 trials as a good starting point. 


The ‘hand-held’ part of HHD is the main limitation to this assessment method because it adds another source of variability, or error. For this reason, the most reliable way to use a HHD is to externally fixate the device, securing it to an immovable structure to create a stable and consistent testing setup.

 (See this blog on measurement error)

Whilst it’s often cited that isokinetics is the gold-standard of muscle testing, this is untrue. There are no data to support the claim isokinetic testing is superior to isometric testing. Data from well-conducted isometric tests can be just as useful as data procured from isokinetic tests. Isokinetic tests involve assessing a person’s strength throughout a pre-defined range of movement at a set movement speed, as such it is a dynamic test. HHD testing involves assessing a person’s isometric strength and as such it is a static test.

You generally get what you pay for - quality typically doesn’t come cheap. That being said the HHD market is very competitive now and that is driving prices down. Check out the comparison tool to cross-check the technical specifications against price.

Sampling frequency is important in the assessment of muscle force production, especially for events that occur quickly. It is important to obtain enough data points to accurately calculate each index of performance. For peak force, which can occur within 300ms from force onset in fast contractions, a sampling frequency of 100Hz is likely adequate to capture the peak. Slower sampling frequencies can also offer useful data, however, the absolute peak response many be missed. 

For rate of force development (RFD) and the assessment of small epochs of the force-time curve we need a great deal more data points to accurately calculate true performance. Sampling frequency for RFD should be a minimum of 500Hz, ideally 1000Hz / >.

Sampling frequency refers to the number of data points of a signal collected per second and it is measured in Hertz (Hz). 1Hz is one sample per second, 100 Hz is 100 samples per second. Sampling frequency is important in the assessment of muscle force production, especially for events that occur quickly, like rate of force development (RFD).

Both devices have the same load capacity (138kg), are certified medical devices and have immediate on screen display of data. The Lafayette has a slower sampling frequency (40Hz vs 100 Hz) and (outside of this site) is slightly more expensive compared to the MicroFet2.

It depends on what you mean by accurate and how you’re using the HHD.  Most dynamometers report very similar reliability and calibration data. For example a reliability ICC inter-rater value of 0.8 shows good reliability of test measures between people conducting the same test, however, this is more likely determined by the experimental set-up than the device itself. 

The calibration data show how accurately the HHD measures force when a standardised series of known loads is applied - often from a laboratory-based machine. These results indicate the range in which the device performs most reliably and the size of any measurement error.

If you’re interested in measuring RFD accurately, then you need to consider the sampling frequency (see sampling frequency question)

HHD measures isometric muscle force, the highest value of which is called peak force - commonly referred to as muscle strength. Data is usually reported in Newtons (N) or in kilograms of force (kg).