Muscle strengthening

Why is adequate strength important

• Muscles provide support for joints (rationale = without adequate muscle support, there is a greater wear & teat in joints)

• Optimum function (rationale = Adequate muscle strength allows the body to keep up with the demands of life. These demands depend on age, occupation and gender)

Indications for muscle strengthening exercise

• Extended periods of immobilisation causing muscle atrophy

• After an injury, patient needs to regain adequate muscle strength to prevent re-injury

• Presence of debilitating diseases

• Effects of postural dysfunction

Muscle strength definition

• Ability of contractile tissue to produce tension and a resultant force based on the placed on that muscle.

• The greatest measurable force exerted by a muscle to overcome resistance during a single maximum effort

Factors affecting muscle strength

• Physiological strength: depends on factors such as muscle size, the cross-sectional area of the muscle and its responses to training.

• Neurological strength of impulse: how weak or how strong the signal is that tells the muscle to contract.

• Mechanical strength: refers to a muscle’s pulling force and the way those forces can be changed using bones and joints as levers

Cardiovascular endurance

The capacity to maintain strenuous activity of multiple muscle groups for prolonged periods of time. In other words, this is aerobic activity that requires the cardiovascular system (heart, lungs, blood vessels) to work together to supply oxygen to your muscles during prolonged physical activity

Muscle work (Isotonic contractions)

• Isotonic contraction = e performed with joint motion whereby the muscle length change

• Concentric contraction = type of muscle contraction in which the muscles shorten while generating force

• Eccentric contraction = The elongation of a muscle while the muscle is still generating force where resistance is greater than force generated, and the muscle lengthen

Isokinetic contraction

When muscle contracts and shortens at a constant rate of speed, despite possible changes in external resistance.

e.g. leg work riding a stationary bike

Dynamometry (isokinetic dynamometry)

• provide accommodating resistance (adjusts resistance according to force exerted by person being tested)

• maximum muscle contraction throughout ROM

• equipment expensive; setup sometimes time- consuming

• Handheld dynamometry = measure maximum force exerted by muscle manually

One repetition maximum (1RM)

A 1RM = maximal load with which a task (movement) can be performed defined as “the greatest load (in kg) that can be fully moved (lifted, pushed or pulled) once, without failure or injury.

• RTF = max number of reps with load less than max, before patient fails to perform properly OR slows done

• Formula

  • 1RM = (0.33 x RTF x load in Kg) + load in Kg

Components of muscle performance

1. Muscle strength

2. Muscle power

3. Muscle endurance

• Muscle power = The maximum force that a muscle or muscle group can generate in a minimum time.

• Power = force x distance / time

  • Therefore to increase power you can:

    • Increase force (heavier weights), increase distance, decrease time (perform movement faster)

Muscle endurance + endurance definitions

• Endurance = The ability to perform low-intensity, repetitive or sustained activities over a prolonged period of time

• Muscle endurance = The ability of a muscle to sustain an isometric contraction or continued (concentric, eccentric) isotonic contraction

muscle endurance conventions:

• increased no. of reps

• low resistance

• prolonged period of time

Clinical application of muscle strengthening

Questions to ask before providing a strengthening intervention

1. What is the patients’ baseline muscle strength for the muscle or muscles affected?

2. What should the muscles strength be to assist the patient reach their previous functional ability?

3. What strengthening intervention should be done, to assist the patient to achieve their previous level of function optimally?

Precautions in pre-strengthening intervention

• severely impaired sensation

• coordination difficulty

• balance difficulty

• decreased cognition

• choose appropriate resistance/weight modalities

• no breath holding (avoid the valsalva manoeuvre)

• be aware of patients medication (some drugs can weaken muscles and tendons, making them more prone to injury)

• stop if patient experiences dramatic increase in pain, dizziness or unusual shortness of breath

Contraindications in pre-strengthening intervention

• in post-surgical conditions — determine the contraindication with the surgeon

• acute inflammation (especially inflammatory neuromuscular diseases)

• pain (if pain in isotonic (concentric or eccentric) then try isometric → if pain during isometric, try again but if pain persists then stop exercise and assess reason for pain

During the strengthening intervention

Observations: muscle fatigue

• discomfort

• pain

• muscle cramp

• visible tremor in contracting muscle

• inability to complete full movement

• compensation of the primary movement with other muscle groups

Procedure in the consultation room

• Explain the purpose of the muscle strengthening exercise/programme to the patient and its ultimate intent help to improve their strength to ultimately improve joint mobility and functional ability.

• Expose the limb to be strengthened, patient suitably undressed. Patient also suitably draped as necessary.

• Choose a stable starting position.

• Demonstrate and explain the movement that the patient needs perform.

• Stabilise appropriately and correct trick movements –ensure that the patient engages the correct muscle group!

Principles of strengthening in the consultation room

• patient must be in a stable starting position with focus on muscle to be strengthened

• smooth and rhythmical movements (avoiding compensatory movements)

• Muscle must be strengthened for all types of muscle work: isometric, concentric and eccentric

• with weak muscles → start strengthening in mid-range, then inner range, then progress to outer range and full range

• Strength training must be done progressively in sensible increments

Progressive strengthening of single muscle or muscle group

• Improving muscle activation from a grade 1 → grade 2

  • e.g. isometric contractions or free active exercise in a gravity eliminated position or progress

  adding appropriate resistance

• Improving muscle activation from a grade 2 → grade 3

  • e.g. free active exercise in a gravity eliminated position, progress adding appropriate resistance then free active exercise in an against gravity position.

• Improving muscle activation from a grade 3 → grade 4

  • e.g. active exercise against gravity, adding appropriate and gradual resistance

• Improving muscle activation from a grade 4 → grade

  • e.g. active exercise against gravity, adding appropriate and gradual resistance

Muscle work training principles

Isometric, concentric and eccentric

• Isometric = Duration: hold for 1-5 seconds, allows peak tension to develop. Joint angle: Strength only gained at or close to the training angle therefore resistance into the range is recommended

• Concentric = Performing the physiological action that occurs in relation to the concentric contraction of the muscle e.g. flexion; extension etc

• Eccentric = When strengthening a muscle eccentrically, the patient performs the concentric movement and then instruct the patient to return to the starting position “slowly” during the eccentric contraction

Methods to alter resistance

1. Change starting position and therefore effects of gravity

2. increasing training volume (number of repetitions and sets)

3. increase load

4. increasing the lever arm length of the affected extremity or body part

5. Alter the range of muscle work (mid-range then inner range then outer range)

   Rationale: Muscles generate the most force when they are at an optimal length — not too stretched and not too contracted. This typically occurs in the middle of the range of motion.

6. speed

Muscle strengthening modalities — the next 10 slides are different types of modalities

A muscle strengthening modality = equipment or bodyweight used to either provide resistance (add load) to a physiological action to promote tensile strength or the ability for a muscle OR group of muscles to produce force

• Pendular exercises

  • used for patients who are very weak but can produce a palpable muscle contraction (e.g. grade1)

  • Horizontal plane circular movement, vertical and horizontal movement.

  • Sway of body assists muscle in moving the limb in a pendular motion.

• Rehabilitation board

  • Used to support a limb for exercises in the horizontal plane.

  • Gradient use:

    • Incline → increases resistance (harder, against gravity).

    • Decline → decreases resistance (gravity assists movement).

      Advantages:

    • Resistance can be adjusted by tilting the board.

    • Useful for bedridden patients.

    • Promotes independence (patient can move without therapist holding limb).

    Disadvantages:

    • Not suitable for all limb movements.

    • Risk of skin friction/pressure → board must be padded.

    • Patient may still need help with positioning and stabilising the board.

• Manual resistance

  • May be used when no other weights are available e.g. when working with a patient who is confined to a hospital bed or when you have no access to weighted equipment.

  • Advantages:

    • You can adjust the resistance through range (increase/decrease or keep it constant)

      Disadvantages:

    • Patient cannot perform exercises which utilises manual resistance independently for home program unless a family member/caregiver can be trained to assist.

    Convention:

    • To supply smaller amount of resistance (weaker patient): shorten the lever arm and apply resistance closer to patient’s joint.

    • To supply greater amount of resistance (stronger patient): lengthen the lever arm and apply resistance further away from patient’s joint.

• Free weights (dumb bells)

  • Resistance can be increased progressively by increasing the size of the load.

  • Advantages = To substitute use of conventional dumb bells, household items such as food cans or water bottles can be used.

  • Disadvantages = Only feasible for upper limb strengthening (free weights are tricky to pick up with your feet!)

• Body weight

  • Good to use when patient has at least a grade 3-4

  • Advantages = no physiotherapist needed

  • Disadvantages = requires full weight bearing of patient

• Cuff weights

• Exercise ball — Most exercises prescribed with an exercise ball require an ability for the patient to be able to weight bear through the upper or lower extremities

• TheraBand — cheap, versatile, and portable tools for resistance training, but they lack precision in measuring load.

• Pulleys

• Hydrotherapy

• Group exercise classes

Overtraining + DOMS + muscle strain

• Overtraining is characterized by a long-term increase of training (exercise) demand without adequate rest or recovery time.

• Delayed onset muscle soreness

  • Any type of activity that places unaccustomed loads (loads which one is not used to) on muscle may lead to delayed onset muscle soreness (DOMS).

  • Delayed soreness typically begins to develop 12-24 hours after the exercise has been performed.

• Muscle strain

  • Muscle strains occur when muscle fibres are unable to cope with the demands placed on

    them.

  • It is a contraction-induced injury in which muscle fibres tear due to extensive mechanical

    stress.

  • Muscle strains can occur when resistance or load is increased premature.

Record keeping

• used for legal obligation, database for comparison and effectiveness of strengthening exercises

• record includes:

  • muscle activated, starting position, exercise description, modality for exercise, volume (no. of reps), frequency (no. of exercise sessions per day/week) and duration

Principles of strengthening weak muscles

• Overload = An increased load or resistance should be applied to muscles to improve muscle performance.

Sub-principles of overload

• To maintain muscle strength do not change load.

• To increase muscle strength progressively increase: load & volume (reps, sets, frequency)

Muscle strength

The greatest measureable force exerted by a muscle to overcome resistance during a single maximum effort

strength training convention

• high load/resistance and a low no. of reps

• not dependant on a time factor

Principled of strengthening weak muscles: Overload

• Overload = increased load or resistance should be applied to muscles to improve muscle performance

Specific adaptation to imposed demands (SAID)

• exercises should be task-specific to prompt the necessary adaptations encouraging motor learning

• e.g. from crutches → walking —- you should do exercises that mimic the gait cycle

Reversibility

• Principle states that activity must continue at the same level to keep the same level of adaptation in muscle tissue. as activity declines, the muscle adaptations will regress.

• loss in muscle performance starts within 1-2 weeks without training

• ‘use it or lose it’

to maintain muscle performance:

• principles to increase strength or endurance must be used

• priority = find ways to carry over training induced improvements into patient’s daily life to prevent reversibility

Types of exercise

• Open kinetic chain exercise

  • movement when distal segment moves freely in a non-weight bearing position. limb movement occur distal to moving joint due to contraction of muscles that cross the joint

  • e.g. biceps or hamstrings curl

• Closed kinetic chain exercise

  • movement of the proximal body segment on a fixed distal segment. the extremity exercised remains in constant contact with the immobile surface, usually the ground

  • e.g. push ups or squats

  • distal segment remains fixed in place

  • promotes co-activation of muscle groups and dynamic stabilisation as well as improved proprioception, balance and neuromuscular control

• Resisted exercise

  • exercise whereby muscles contract against an external force

    • benefits = improved mobility, decreased joint stress, reduced risk of soft tissue injury, increased strength of connective tissues (e.g. tendons)

    • aesthetic and physiological benefits of resisted exercise = enhanced feelings of wellbeing and improved perception of disability