One of the most widely used methods of assessing muscle strength is Manual Muscle Testing, which gives a physiotherapist a general understanding of how weak a patient’s muscle is. But what it fails to do, is to provide a clinician with a numeric quantification with which the muscle thrusts. Although being a standard clinical evaluation tool, its reliability and validity are highly questionable. The limitations of MMT arise from the nature of the procedure used as the tester must provide external resistance, which may vary considerably between testers. MMT also comes with a complicated procedure and it takes an experienced clinician to correctly assign the exact grade to a muscle. This method of assessment also annihilates the possibility of measuring a patient’s accurate prognosis as it is impossible for a human therapist to precisely determine the amount of force generated by a muscle. Let’s say a clinician is testing a twenty-five-year-old amateur boxer and a sixty-year-old man for muscle strength. Let’s say the tester gives a grade of 5/5 for the boxer because of his fantastic strength, and also 5/5 for the sixty-year-old man because his strength appears normal for his age. Then, the ability to distinguish between the two becomes lost.
The gold standard for measuring muscle strength is through the use of a device called an Isokinetic Dynamometer (IKD).
It was invented in 1969 and is the most accurate and the most valid tool invented to date, however, its feasibility has been and always will be low. For decades, physiotherapists have been seeking a tool that helps them measure muscle strength accurately. In order to overcome the limitations of MMT and IKDs, machines called Hand-Held-Dynamometers (HHD) have been developed in order to assist physiotherapists to measure muscle strength objectively. These machines are generally small, portable, and accurate devices that provide a numerical quantification of muscle force. This tool allows a physiotherapist to assess without the usage of a complicated procedure and also eliminates the need for an experienced clinician. Furthermore, clinicians tend to assess muscle strength using a single trial, which saves a lot of time. It also provides consistency, and accuracy unmatched by manual methods.
Various studies have been conducted to prove its reliability and validity. A study conducted by Lan Le and Jessica Jensen concentrated on intratester reliability and validity. Intratester reliabilities of peak torque and work are excellent in both elbow and knee measurements with the HHD. Similar studies conducted by Cadogan et al, in 2011 show a good to excellent reliability of the HHD in practice.
Another study conducted by Timothy Stark et al correlated Hand Held Dynamometry to Isokinetic Dynamometry, which as mentioned earlier is the Gold Standard when it comes to muscle strength quantification. Their objective was to examine the current evidence regarding the reliability and validity of hand-held dynamometry for the assessment of muscle strength in the clinical setting. They reviewed 19 studies whose objective was the same, correlating HHD and IKD. All studies showed a positive Pearson’s correlation coefficient, (r>0) which means a positive correlation exists between the two. They concluded that considering hand-held dynamometry’s ease of use, portability, cost, and compact size, compared with isokinetic devices this instrument can be regarded as a reliable and valid instrument for muscle strength assessment in a clinical setting.
Now, let us dive into a couple of areas where hand-held dynamometry can be used!
Sports
Sports injuries are commonly caused due to overuse of anatomical structures or are a result of high-velocity thrusts against certain structures like ligaments and tendons. In the field of sports medicine, hand-held dynamometry is gaining considerable interest over isokinetic testing, since the equipment is not expensive and easy to use on the field or training area of the athlete.
With the help of HHDs, the prognosis of various sports injuries like ACL tears, PCL tears, and muscle strains can be precisely documented. Sports rehabilitation can be a tedious and time taking process, especially if the injury sustained was severe. For a person to return to sports, a specific protocol tailor-made for the individual must be done. One of the most important aspects for return to sports is pain-free muscle exertion. This can be measured quite easily through the use of an HHD.
Muscle Imbalance and Postural Dysfunction
When one side of the opposing muscles is stronger than the other, you have a muscle imbalance. Without correction, it can lead to postural instability which in turn causes low back pain and knee ailments. With the help of HHDs, the exact amount of imbalance can be measured and a strengthening protocol for the weaker muscles can be implemented. A few common imbalances include – The Quadriceps-Hamstring imbalance, The Chest-Back imbalance, and the Right-Left imbalance. The treatment for these conditions can be supplemented by the use of HHDs.
General Clinical Setting
People suffer from multiple musculoskeletal conditions that hamper their muscle strength every day. A few of them include frozen shoulder, tendonitis, tendinosis, and sprains. Sever diseases that require hospital admission, such as stroke, also cause generalized muscle weakness. With the help of normative values, it becomes easy for a therapist to identify his goals of treatment.
These are age-specific and gender-specific values obtained through extensive research and study. These values provide large amounts of credibility to the use of HHD as it tells us what is normal or in the range of normal. Clinicians can use the HHDs to their advantage and formulate treatment protocols effectively by comparing the patient’s strength to that of what is normal.
HHDs are growing in popularity and rightfully so! These portable and efficient machines provide therapists with everything they need clinically when it comes to muscle strength. These tiny, technology-filled devices are slowly but gradually changing the field of physiotherapy through the ideology of data drive.
References:
https://www.researchgate.net/publication/51124614
https://www.hindawi.com/journals/bmri/2019/8194537/
https://pubmed.ncbi.nlm.nih.gov/22424705/
https://pubmed.ncbi.nlm.nih.gov/30377716/
http://insportscenters.com/common-muscular-imbalances-and-how-to-correct-them/
