Recording Muscle Length: Techniques For Accurate Measurement

Muscle length is a measure of a muscle's ability to lengthen and allow joints to move through their full range of motion. This is important for functional activities and rehabilitation professionals who need to assess and treat patients. There are several methods for measuring muscle length, including the use of a universal goniometer, an inclinometer, or linear forms of measurement such as a tape measure. In addition, there are more advanced technologies such as magnetomicrometry and ultrasound that can provide more accurate measurements. Measuring muscle length is fundamental to understanding the mechanics and energetics of locomotion and informing models of motor control. For individuals, tracking muscle growth over time can be done through visual inspection, body measurements, weightlifting progression, and body composition analysis.

Using a tape measure

Neck:

Measure at the smallest part, just above the Adam's apple, with your head erect and muscles relaxed. If you have a double chin, measure below it to avoid a slant.

Upper Arm, Flexed (Biceps):

Raise your arm to shoulder level and fully contract your biceps, ensuring the back of your hand faces the ceiling. Place the tape squarely around the biceps at its most prominent point, avoiding any slant.

Upper Arm, Straight (Triceps):

Hold your upper arm horizontally in line with the shoulder joint, keeping it relaxed. Place the tape around the largest part, usually just below where the deltoid joins the arm.

Forearm:

Keep your arm straight, wrist straight, and clench your fist firmly. Measure at the largest part of your forearm, just below the elbow.

Wrist:

Place the tape directly next to the base of your hand, between the bony knobs and the hand. Hold your hand open with the palm up, fingers straight, and in line with the forearm.

Chest:

For men, measure immediately under the armpits, ensuring the tape crosses the shoulder blades in the back and the nipples in the front. Keep your torso erect, breathe quietly, and relax your muscles. For women, take measurements above the level of the breasts in the front. For a contracted chest measurement, exhale all air and flatten your chest. For an expanded chest, inhale the largest volume of air and expand your chest muscles.

Waist:

Measure at the smallest part, usually just above the navel, with your body erect and natural. Avoid the temptation to make your waist smaller while measuring.

Hips:

Stand with your feet together and muscles relaxed. Measure at the broadest part of your hips, from side to side, and the deepest part of your buttocks from front to back.

Thigh:

Spread your feet about six inches apart and distribute your body weight evenly. Keep your thighs relaxed and measure at the largest part, usually in the crease just below the buttocks.

Knee:

Place the tape across the middle of your kneecap.

General Tips:

• Use a cloth tape measure, ensuring it is in gentle contact with the skin without being too loose or tight.
• Measure both sides of the body to accurately track progress and symmetry.
• Be consistent in your measurements, maintaining the same conditions and equipment each time.
• Record your measurements in a health journal or digital platform to track your progress over time.

Using a universal goniometer

The universal goniometer is the most widely used type of goniometer, which is the most common instrument for measuring a joint's range of motion. It comes in two forms: short-arm and long-arm. The short-arm goniometer is used for smaller joints like the wrist, elbow, or ankle, while the long-arm goniometer is more accurate for joints with long levers like the knee and hip joints.

To use a universal goniometer, first, familiarize yourself with the tool. A goniometer has two arms: one that is attached to the circle with the angle degrees on it, and a movable arm that does the measuring. The movable arm should be aligned with the moving limb, and you should then look at the goniometer to see the angle degree that the moving arm is pointing to. The centre of the goniometer, also called the fulcrum, should be placed on the fulcrum of the joint you are measuring. The centre of the goniometer should be aligned with the centre of the joint.

It is important to ensure the patient does not move their body while the joint is being moved, to ensure accurate measurement. The patient should be counselled in advance, and consent for examination is necessary. The examination must be conducted in broad daylight, with the joint undergoing evaluation and the surrounding area well exposed.

To measure the range of motion for a shoulder joint, for example, you would start by holding the arm straight down against the body. Then, move the arm slowly upwards, stretching as far as possible. Measure the angle using the goniometer. To measure the backward flexion of the shoulder, start with the arm down by the body and move it backward before measuring.

Using an inclinometer

An inclinometer is a device used to measure angles and is one of the three main tools used to assess muscle length, the others being the universal goniometer and linear forms of measurement such as a tape measure. It is commonly used in physiotherapy to measure the range of motion (ROM) of joints and is very similar to a goniometer. The ROM is the amount of movement that a joint can make. For example, a physiotherapist might use an inclinometer to measure the angle between the thigh and the shinbone to assess the alignment of the knee joint.

There are two types of inclinometers: manual and digital. Manual inclinometers, sometimes referred to as "bubble inclinometers", have a fluid-filled face in a circle. The fluid is a combination of coloured and clear fluid, and the fluid interface moves with gravity. The movement of the interface is used to read the measurement off a rotating 360-degree face dial. Manual inclinometers are relatively inexpensive (around $50 each) and do not require batteries, but they can be difficult to read due to the small print face. Digital inclinometers, on the other hand, are electronic gravity sensors that can standardise a zero-measuring reference with the click of a button. They are approximately the size of a pocket watch and are typically connected by an electronic cord. One end, the "master", is placed at the top of the spine, while the other, the "slave", is placed at the lower segment of the spine. Digital inclinometers are easy to use and automatically calculate the true angle, but they can be expensive, often ranging into the hundreds of dollars.

When using an inclinometer, it is important to first prepare the patient and the environment. The patient should be comfortably positioned, either sitting or lying down, depending on the joint being assessed. Any clothing or obstructions that may interfere with the measurement process should be cleared. The patient should also be familiarised with the procedure to ensure cooperation and relaxation during the assessment. The specific joint or joints to be assessed should then be identified. Common joints for ROM measurement include the shoulder, elbow, wrist, hip, knee, and ankle. The inclinometer is then positioned either directly on the joint's axis of rotation or on adjacent body segments, depending on the joint's anatomy and the measurement technique being employed.

To perform the ROM measurement, the patient is instructed to move the joint through its full range of motion while keeping the inclinometer aligned and stationary. Smooth, controlled movements are encouraged to prevent compensatory motions or muscle guarding. As the patient moves the joint, the corresponding angle displayed on the inclinometer is read and recorded at various points throughout the ROM. Any limitations, pain, or discomfort experienced by the patient during the assessment should be noted. This process may need to be repeated for each plane of motion relevant to the joint being assessed, including flexion/extension, abduction/adduction, internal/external rotation, and circumduction. Once the ROM measurements have been obtained, they are interpreted in the context of the patient's clinical presentation, functional goals, and treatment plan.

Using an InBody device

InBody devices provide precise measurements of body composition, including muscle mass, body fat, and water levels. They use advanced bioelectrical impedance technology, which involves sending a low-level electrical current through the body to measure resistance. This method is highly precise as resistance varies based on the composition of body tissues.

To prepare for an InBody test, it is important to avoid food and physical activity beforehand, as these can affect hydration levels and muscle mass readings. Consistency in testing conditions, such as the time of day and hydration levels, is crucial for accurate results. It is also important to use the same method and device for progress tracking, as different devices may use different technologies and algorithms for measuring muscle mass.

InBody devices are available in gyms and healthcare settings, and can also be purchased for home use. They are trusted by healthcare providers, fitness professionals, and researchers worldwide for their accuracy and precision. The detailed data provided by InBody scans can guide personalized health, fitness, and nutrition plans, helping individuals to optimize their efforts and make informed decisions for better health and wellness.

In addition to tracking muscle growth, InBody devices can also be used to monitor muscle mass loss, which can be important for individuals experiencing muscle wasting due to certain medical conditions or treatments. By providing insights into muscle mass, body fat, and water distribution, InBody devices can help identify areas for improvement and inform dietary and exercise choices.

Measuring the bicep

To measure your bicep, you will need a flexible tape measure, ideally a tailor's tape measure. If you do not have one, you can use a string or a ribbon and then measure it with a ruler. You can also wear a thin shirt or t-shirt if you prefer, as long as it does not add bulk to the measurement. However, for the most accurate results, it is recommended to measure directly on the skin.

Stand up straight with your arms relaxed at your sides. If you are measuring yourself, let your arm hang down beside your body and keep your muscles relaxed. Wrap the tape measure about three to four inches below your armpit, which is generally the widest part of your bicep. Ensure that the tape is flat against your skin and not twisted, and do not pull or stretch it too tightly. Take several measurements for accuracy, rounding up to the nearest half-inch.

For consistency, it is important to measure both biceps and to do so at the same time of day under consistent conditions. This will allow you to compare your arms and figure out if one side needs more work.

Frequently asked questions