Multiple times a week, I get asked, “Which handheld dynamometer (HHD) do you like?” If you’re looking for a simple guide to compare all the different devices on the market, you can view one here. However, my answer is always: “It depends on your setup.”Most handheld dynamometers are nearly the same in regard to specifications, so it really depends on which tests you want to do and what fixation sites you have at your disposal, says @MuyVienDPT. Click To Tweet
Most devices are nearly the same in regard to specifications, so it really depends on which tests you want to do and what fixation sites you have at your disposal. This article will give you confidence in your final device of choice because you have made all the considerations to use an HHD reliably for good data.
What Is a Handheld Dynamometer and Why Is the Market Expanding?
Dynamometers are force gauges that measure the amount of force pushed into or pulled against the device (figure 1). The device then shows the amount of force produced on its screen, or via an app if it is a Bluetooth-based device. HHDs specifically fit in your hands and are portable, hence the name. Compared to popular, research-grade isokinetic dynamometers found in labs, such as the HUMAC Norm and Biodex, they are cheaper and portable. However, they may not be as accurate or reliable and may have lower load capacities (table 1).1–5
Different types of muscle strength tests can be performed with an HHD. A “make” test means the dynamometer is held still by the test proctor or an external fixation (figure 2), and the tester pushes into the device as hard as possible. A “break” test is when the tester holds their limb as still as possible as the test proctor directs a force to overcome the tester’s resistance. This type of test often results in larger values since it biases a muscle group’s eccentric capability.
In the past, HHDs were only found in labs and clinical settings; however, their rapid growth into the performance world may be due to two main reasons.
- Over the past decade, you have likely attended some kind of educational session called “Bridging the Gap Between Rehab and Performance.” Such sessions have enhanced communications between rehab and performance departments. Performance coaches now understand what should be measured in the rehab space (table 2), and manufacturers are taking notice. For example, Vald Performance, a company well-known in the performance space for its force plates and hamstring measurement device, just recently released its version of a push-and-pull HHD.
- Another reason the market has been exploding is that, despite evidence supporting objective measures, rehab professionals have been shown not using objective methods to measure strength. For example, 56% of physical therapists use a subjective “feel” for quad strength measurement when they clear their athletes for return to sport.11 These daunting statistics have been popularized, and rehab professionals now see the need to purchase devices to ensure the safety of their athletes.
Both professions have found a need to measure isolated strength. Although specific decisions often lean on one discipline over another depending on an athlete’s recovery timeline (i.e., physicians giving final clearance for an athlete returning to sport), the act of data collection is not exclusive to any profession.
Hopefully, you see the exciting uses and opportunities for handheld dynamometers. Now we will focus on considerations for making a purchase.
Determine Your Process Before You Make Your Purchase
Data is only applicable to decision-making if it is valid and reliable. As previously shown in table 1, fixation greatly influences whether your HHD data is reliable and valid. For this reason, your purchasing decision should be largely about how you plan to fixate your device as you design quick and efficient methods to test your athletes. Often assumed to be easy, fixation is actually the largest problem users have (figure 3), as they end up purchasing devices before they fully account for what tests they want to perform and how they will perform them. They buy the devices and then realize their environment does not have proper objects to fixate to, nor do they have good attachments for their devices.Your purchasing decision should be largely about how you plan to fixate your handheld dynamometer as you design quick and efficient methods to test your athletes, says @MuyVienDPT. Click To Tweet
Companies such as Vald (Force Frame) and Kangatech (KT360) have developed dynamometers attached to frames, which can be excellent options as long as you understand they are not capable of “break” tests and are relatively bulky compared to their handheld counterparts. For one reason or another, many professionals prefer the portability of HHDs. Therefore table 3 has different fixation considerations you should have when purchasing an HHD, even including which tables are in your environment (figure 4).
Excellent fixation is key during testing, but certain circumstances call for non-fixated methods. Say, for example, you have a team of 30 athletes that you would like to test for hip strength. That’s 30 athletes, two hips each, three trials each limb, and 3–5 seconds each trial… You get it; it’s a lot of time.
I would feel comfortable without belt or wall fixation because the evidence shows good intrarater reliability, and I would be the one administering these tests over time anyway. I would caution myself in comparing my peak force norms to those in the research or from colleagues since the evidence suggests strength and sex influence testing scores.16 The data I would then use is symmetry and muscle group ratios since all of my data has a steady degree of systematic error (constant and stable error). I can even still use the absolute values if I compare them within my own database over the years if I was still the one taking them each year.
This example is just one of many scenarios emphasizing the need to consider your testing process before purchasing a device. There are many other considerations you may have to make (table 4) to determine which HHD is right for you.
Finally! You planned out all the different ways you will test isolated muscle strength and decided on your purchase. Now comes a whole different process consideration: what is the quickest way to test muscle regions that requires the least amount of position changing between you and the athlete?Performance coaches now understand what should be measured in the rehab space, and manufacturers are taking notice, says @MuyVienDPT. Click To Tweet
I will largely save this for another article—in the meantime, see figure 5, which will help accelerate your testing methods with your new dynamometer. Learning curves are expected with any new technology, and you will surely refine the process as you use your HHD more. Just be glad you approached technology correctly by determining your needs and process before the purchase.
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