Muscle Strength Measurement PDF

**MEASUREMENT OF MUSCLE STREGTH AND JOINT RANGE** **Introduction** Muscle strength is the ability of a muscle or a group of muscles to exert force against resistance. It is a crucial component of physical fitness and overall health, playing a vital role in daily activities, sports, and rehabilitat...

**MEASUREMENT OF MUSCLE STREGTH AND JOINT RANGE** **Introduction** Muscle strength is the ability of a muscle or a group of muscles to exert force against resistance. It is a crucial component of physical fitness and overall health, playing a vital role in daily activities, sports, and rehabilitation processes**.** **Components of Muscle Strength** **F**orce Production: The maximum amount of force that a muscle or muscle group can generate during a single contraction. **E**ndurance: The ability to sustain muscle contractions or continue repetitive muscle activity over time. **M**uscle Power: The ability to exert force quickly, important for activities requiring rapid movements. **Factors Influencing Muscle Strength** **Muscle Size:** Larger muscles generally produce more force due to greater cross-sectional area. **Muscle Fiber Type:** **Type I Fibers (Slow-Twitch):** More endurance-oriented, less powerful but fatigue-resistant. **Type II Fibers (Fast-Twitch):** More powerful and better for strength and speed activities but fatigue faster. **Neuromuscular Coordination:** Efficient activation and coordination of muscle fibers and motor units enhance strength. **Age:** Muscle strength typically peaks in the late 20s to early 30s and declines with age due to sarcopenia (age-related muscle loss). **Gender:** Generally, men have greater absolute muscle strength than women due to higher muscle mass and testosterone levels. **Training and Conditioning:** Regular resistance training increases muscle strength by hypertrophy (muscle growth) and improved neuromuscular efficiency. **Nutrition:** Adequate protein and nutrient intake support muscle repair and growth. **Genetics:** Genetic factors influence muscle fiber composition, size, and overall strength potential. **Types of muscle contraction** 1. Isometric contraction: An isometric contraction is a static contraction with variable/accommodating resistance that does not result in changes in muscle length. There is no movement, and no external work is done by the muscle. Hence isometric exercises are exercises that keep the body in one position. An example of isometric contraction is arm wrestling while examples of isometric exercise include the plank and wall push. 2. Isotonic contraction: here, tension remains the same, but the muscle\'s length changes. Thisis to say that there is movement in isotonic contraction. There are two types of isotonic contractions: concentric and eccentric contractions. a. Concentric contractions involve shortening of the muscle, so the origin and insertion of the muscle move closer together. This occurs when a muscle lifts or moves a weight that is less than its maximum tetanic tension hence it shortens, movement and work is done. b. Eccentric contractions involve lengthening of the muscle as it gives in to an external force that is greater than the contractile force exerted by the muscle. The muscle does not length per say it just returns from its shortened position to its normal position. **MEASUREMENT OF MUSCLE STRENGTH** Muscle strength can be measured using the following methods: 1. **1 Repetition Maximum(1RM)**: This is the measurement of the greatest load (in kg) that can be fully moved (lifted, pushed, or pulled) once without failure or injury. This type of measurement is frequently used by athletic weight lifters. It can be predicted using the formular: 1RM = (0.033 x RTF x load) + load. Where RTF stands for repetitions to fatigue which stands for the maximum number of exercise repetitions one can make using a load that is less than the maximum amount you can move. Eg if a person can lift a 50 kg weight for nine repetitions before tiring significantly, their estimated 1RM is: 1RM = (0.033 x 9 x 50) + 50 = 14.85 + 50 = approximately 65 kg 2. **Manual Muscle Testing (MMT) :** This is used to test the degree of strength or weakness of an individual muscle or muscle group as the perform an action or movement against gravity or resistance. MMT relies on the strength of the clinician i.e the clinician must be stronger than the patient. Scales available for completing manual muscle testing include: a. Medical Research Council (MRC) Scale - also known as the Oxford Scale b. Daniels and Worthinghmans Manual Muscle Testing Scale c. Kendall Muscle Testing Scale Pinch grip dynamometer: This type of dynamometer is specifically designed to measure pinch strength in the fingers and thumb. It consists of two plates that are squeezed together by the patient's fingers, and the amount of force generated is measured and displayed on a gauge. Isokinetic Dynamometer: This type of dynamometer is used to measure muscle strength and function through a range of motion. An isokinetic dynamometer measures and controls the speed of joint movement during muscular contractions. It is commonly used in sport medicine and rehabilitation. The equipment works by applying resistance to the movement of the joint and controlling the speed of the movement. This allows for a more accurate measurement of muscle strength throughout the range of motion of a joint, and can be particularly useful in identifying muscular imbalances or weaknesses in athletes or individuals recovering from injury. Isokinetic dynamometers are typically computerized and can provide real-time feedback to both the clinician and the patient, allowing for adjustments to be made during the exercise session. They are also customizable to the specific needs of the patient or athlete, and can be used for a wide range of exercises and movements, including upper and lower body exercises, as well as rotational and multidirectional movements. **4.Functional Tests:** Sit-to-Stand Test: Measures lower body strength by counting how many times a person can stand from a seated position within a set time. Timed Up and Go (TUG) Test: Assesses functional mobility and lower body strength by timing how quickly a person can rise from a chair, walk a short distance, turn, and return to the chair. MEASUREMENT OF JOINT RANGE OF MOTION(ROM) Joint range of motion the capability of a joint to go through its complete spectrum of movements. It can be passive , active -assisted / assisted active or active. Passive range of motion(PROM): is the ROM that is achieved when an outside force (such as a therapist or a Continuous passive motion (CPM) machine) exclusively causes movement of a joint and is usually the maximum range of motion that a joint can move. Usually performed when the patient is unable or not permitted to move the body part. Active-assisted range of motion (AAROM): is when the joint receives partial assistance from an outside force. Usually performed when the patient needs assistance with movement from an external force because of weakness, pain, or changes in muscle tone. Active range of motion (AROM): is the ROM that can be achieved when opposing muscles contract and relax, resulting in joint movement. For example, the active range of motion to allow the elbow to bend requires the biceps to contract while the triceps muscle relaxes. Active range of motion is usually less than passive range of motion.\[4\] Usually performed by the patient independently and when the patient is able to voluntarily contract, control, and coordinate a movement. Goniometry is the most common method of measuring joint range with the aid of an instrument called Goniometer. It refers to the measurement of angles, which in rehabilitation settings is the measurement of angles in each plane at the body\'s joints.  The goniometer has 3 parts: the stationary arm, the fulcrum and the movement arm. **End-feel** End feel is the quality of tissue resistance to motion at the end of PROM. It is the barrier to movement that the clinician feels when slight over-pressure is applied at the end of the joint motion that prevents further movement. There are 2 types of end feel : 1) normal end feel 2) Abnormal end feel. [Normal end feel]: An end feel is considered normal when the structures that limit movement are from the normal anatomy of the body. *Types of normal end feel* 1. Soft end feel: this is caused by soft tissue approximation. It occurs when two soft tissue masses meet one another, limiting further movement. The quality of resistance is soft, and this gradually increases as the soft tissue is compressed between body parts. An example is knee flexion where the soft end feel is caused by contact between the soft tissue of the posterior leg and posterior thigh. 2. Firm end feel: this end feel can be : a) muscular b) ligamentous 0r c)Capsular. 3. Hard end feel: this is caused by bone on bone and occurs when the approximation of two bones stops the ROM. Quality of the resistance felt is very hard and abrupt, with further motion impossible. Example is seen in elbow extension where there is contact between the olecranon process of the ulna and the olecranon fossa of the humerus. [Abnormal end feel]: End-feel is considered abnormal when structures other than normal anatomy stop joint movement. *Types of abnormal end feel* 1. Empty: here there is no real end-feel with no mechanical limitation to the end of the range. No resistance is felt. Pain typically prevents the body part from moving through the available ROM. Examples are Fracture, Abscess, Bursitis, Acute joint inflammation. 2. Soft: this occurs sooner or later in the ROM than is usual or in a joint that normally has a firm or hard end feel. Feels boggy (mushy with a soft quality to it). Examples Soft tissue oedema, Synovitis 3. Firm: Occurs sooner or later in the ROM than is usual or in a joint that normally has a soft or hard end feel. Examples are seen in Increased muscle tone such as hypertonia or spasticity, Connective tissue shortening. 4. Hard: Occurs sooner or later in the ROM than is usual or in a joint that normally has a soft or firm end feel. A bony grating or bony block is felt. This can be seen in fracture, Osteoarthritis, Chondromalacia, Myositis ossificans, loose bodies in joint. 5. Springy : here, a rebound is seen or felt during movement. It can be felt in Internal derangement or torn meniscus. 6. Spasm: this is an involuntary muscle contraction that prevents normal ROM. It is often accompanied by pain - more indicative of an acute or severe lesion. Where no pain is present, it may be an increase in muscle tone secondary to central nervous system involvement. Spasms are felt in acute protective spasm, acute arthritis, fracture, lesion of the central nervous system. 7. Loose: this is movement beyond expected anatomical limits and is often felt in extreme hypermobility, ankle instability, shoulder instability etc.