Strengthening principles

Question 1

Give factors that can limit muscle strength

Answer 1

Malnutrition, neuromuscular disease, immobility, disuse and ageing.

Question 2

What is the overall aim of a strengthening regime?

Answer 2

The overall aim of any strengthening regime is to increase muscle power and/or endurance. This occurs initially via neural adaptation and later through muscle fibre hypertrophy and other adaptations such as increased mitochondrial density.

Question 3

What type of exercise should muscle strengthening programmes be composed of?

Answer 3

Muscle strengthening predominantly consists of active resistance exercises. Exercises need to adhere to the principles of strengthening, be tailored to the individual patient, and be suitable for their current muscle strength (MRC grading).

Question 4

List the key principles of muscle strengthening

Answer 4

-Overload principle: Neuro-muscular adaptation occurs when the exercise volume (comprised of intensity and duration) exceeds its typical demands. Without overload, strengthening does not occur

-Work to fatigue: Fatigue is the reversible decline in the output of a muscle due to an accumulation of metabolic by-products. It is a marker that overload has occurred. Signs of fatigue include:
* Shaking / tremor
* Loss of quality / control of the movement
* Inability to work the muscle through full range

-Specificity: Improvements in muscle performance will correspond with the training regime. Therefore the type of training (power Vs endurance), the range of muscle trained, type of muscle contraction (concentric/eccentric/isometric) and the speed/tempo of the regime should replicate how the muscle needs to be used functionally by the patient.

-Progression: Strengthening regimes need to be progressed regularly

-Dimininishing returns: As muscle adapts to meet the demands of an exercise programme, the same regime becomes less challenging over time and therefore strength gains will reduce. This is known as the law of diminishing returns.

-Reversability: If a strengthening programme is not maintained (for example a patient does not comply with their home exercises), any gains in muscle strength will be lost.

Question 5

Which of the FITT principles are most important for strengtehining?

Answer 5

Setting the correct intensity of exercise is arguably the most important and the most difficult to achieve, especially in the patient population. Most research regarding intensity for strengthening regimes is based on healthy populations and follows a 1 rep max (1RM) formula. For a patient population, testing 1RM is frequently problematic, therefore working around the patient’s 10-12 rep maximum (an exercise which they can perform around 10 times before they reach limiting fatigue) is pragmatic and equates to around 70% of their 1RM.

Question 6

What frequency is required for strengthening programmes?

Answer 6

3 x weekly for MRC grades 4 to 5
Daily for MRC grades < 4

Question 7

What intensity is required for strengthening programmes?

Answer 7

60-80% 1RM
10 rep max (around 70% 1RM)

Question 8

What type of exercise is required for strengthening programmes?

Answer 8

Consider whether the muscle’s function is predominantly power or endurance. When strengthening very weak muscles, start with power, then build endurance. Include specificity principles

Question 9

Give the time suitable for strengthening programmes

Answer 9

3 sets of 8-12 repetitions
1 minute rest between sets (reduces cumulative fatigue)W

Question 10

What are the physical principles utilised in strengthening?

Answer 10

-Stops and starts
-Reduced momentum (slowed/varied speed)
-Resisted movement (against gravity, auto-resisted, free weights, theraband, body weight, water resistance)
-Increased friction

Question 11

Which physics law does ‘stops and starts’ follow?

Answer 11

Newton’s 1st Law
Increases muscle work required to re-start the movement.

Question 12

Which physical law does ‘reduced momentum’ follow?

Answer 12

Newton’s 2nd Law
By slowing and/or varying the speed, greater muscle force is required to elicit a change

Question 13

Which physical principle does ‘resisted movement’ follow

Answer 13

Increases the muscle force required to move the limb

Question 14

Which physical law does ‘increased friction’ follow?

Answer 14

Newton’s 3rd Law
Increases muscle work required to start or sustain the movement.

Question 15

After how many sets/reps should an exercise be progressed?

Answer 15

As a guide, once 3 sets of 12 reps can be performed with good form (no cheat movements), the exercise/s should be progressed.

Question 16

How can strengthening programmes be progressed?

Answer 16

• Use different types of muscle contraction (concentric => eccentric)
• Strengthen the whole muscle range (Mid => inner => outer)
• Lengthen the lever (e.g. bent arm => straight arm for shoulder flexors)
• Add functional exercise (specificity)
• Vary speed – include ballistic (e.g. jumping) exercises if MRC grade 4+
• Increase resistance (heavier weight, progress theraband, use body weight)

Remember to strengthen within the MRC grade that the patient presents with. If the exercises are too easy for the MRC grade, they will be ineffective (no overload). If the exercises are too difficult for the MRC grade i) there is a risk that the exercise may be unsafe and ii) the muscle will not have been strengthened through range (i.e. the inner & outer range would remain significantly weaker).

Question 17

Which therapeutic principles can be followed to increase engagement with exercises?

Answer 17

• Use of targets (especially to work through range)
• Motivation (use of voice) & correction if required
• Competition (with self or others)
• Variety of exercise & individual approach (consider patient age & interests)
• Instruction & demonstration
• Explanation of potential benefits

Question 18

List the practical considerations when carrying out a strengthening programme?

Answer 18

• Patients should be appropriately undressed to allow the Physiotherapist to visualise the affected muscle group (need to see signs of fatigue).
• Consider the optimal starting position for each exercise from both patient comfort and exercise effectiveness perspectives
• Include a localised light warm-up for the body area that is being treated e.g. wrist circling for 1-2 minutes prior to wrist extensor strengthening
• Use any available equipment to improve efficacy and to add interest for the patient
• Always give the patient at least 2 exercises that are suitable for home use with clear instructions for frequency, reps and sets

Question 19

How is muscle strength tested?

Answer 19

There are a variety of ways to assess the strength of skeletal muscle including the use of isokinetic machines, handheld dynamometry and manual muscle testing.
Due to the benefits of being simple, cheap and a practical way of assessing muscle strength with limited requirement for equipment, the Medical Research Council (MRC) grading scale is widely used in medical and physiotherapeutic practice.

Question 20

Define MRC grade 0

Answer 20

No contraction of the muscle
Despite the patient co-operating with the instruction, there is no visible or palpable muscle contraction.

Question 21

Describe MRC grade 1

Answer 21

Flicker of contraction
Some muscle contraction is seen and/or palpated but patient is unable to move through full available range even with gravity counterbalanced

Question 22

Describe MRC grade 2

Answer 22

Can move through full available range with gravity counterbalanced
PROM should be equal to AROM with gravity counterbalanced

Question 23

Describe MRC grade 3

Answer 23

Can move through the full available range against gravity and with a hold
PROM should be equal to AROM against gravity

Question 24

Describe MRC grade 4

Answer 24

Can move through the full available range against a minimal resistance.
Using a measured resistance e.g. a light hand/ankle weight, can quantify this more reliably

Question 25

Describe MRC grade 5

Answer 25

Can move through the full available range against a maximal resistance.
Maximal resistance can be provided by a heavy hand/ankle weight, the therapist or the patient’s own body weight.
Grade 5 can also be defined as “normal function” which includes work as an agonist, antagonist, synergist, fixator, eccentrically, concentrically for short burst and sustained activity.

Question 26

Describe the MRC testing procedure

Answer 26

• Unclothe the part adequately to allow palpation and observation of the muscle to be tested. Give clear explanations to the patient and if necessary demonstrate the required movements.
• Test unaffected side first. You can assume this will be grade 5, therefore test for grade 5 only.
• For the affected side, check the available range by passive movement
• Then, starting from grade 0, progressively test the affected side. Stop progressing through the grades if the patient cannot achieve the next grading. Record the highest grade achieved /5 (e.g. 3/5)

Question 27

Describe how to test for grade 0-2

Answer 27

• Position the patient to eliminate the effect of gravity on the movement. You will need to support the limb either manually or using a re-ed board.
• Check for a contraction visually and by palpation of the muscle belly
• Use the mid-range (strongest) to assess for grade 1 contraction
• For grade 2, check that the movement can be completed through full available range.

Question 28

Describe how to test for grade 3

Answer 28

• Position the patient to allow the movement to occur against gravity
• Check that movement can be completed through full range
• Isolate the movement to prevent any trick movements

Question 29

Describe how to test for a grade 4

Answer 29

• Test as for grade 3 but with an added small resistance
• For upper limb testing suggest ≤0.5kg hand weight
• For lower limb testing suggest ≤1kg ankle weight

Question 30

How to test for a grade 5?

Answer 30

• Test as for grade 4 but with maximal resistance
• The resistance may be applied by a heavy hand/ankle weight or the therapist – you will need to position yourself at a mechanical advantage and ensure you can resist the movement evenly throughout range.
• If the muscle group allows for it, the patient’s own body weight may be used as a maximal resistance
• Consider whether the muscle can work effectively as an agonist, antagonist, synergist, fixator, eccentrically, concentrically for short burst and sustained activity.

Question 31

Describe the composition of muscle fibres

Answer 31

Myofilaments
Myofibrils
Muscle fibres
Muscle fibre bundle
Muscle

Question 32

Describe normal muscle

Answer 32

Normal muscle displays a large variance in fibre type distribution, not only between muscles but also between individuals, particularly the genders

Question 33

Describe slow twitch muscle fibres

Answer 33

Type 1
High concentration of myoglobin enabling aerobic energy metabolsim

Question 34

Describe fast twitch muscle fibres

Answer 34

Type II
Low concnetrtaion of myoglobin enabling anaerobic enegry metabolism

Question 35

Describe the properties of type I muscle fibres

Answer 35

-slow oxidative
-slow and small motor unit
-slow conduction rate
-high resistance to fatigue
(aerobic resp, endurance based exercise)

Question 36

Describe the properties of type IIa fibres

Answer 36

-fast oxidative glycolytic
-fast fatigue resistant and medium sized motor unit
-fast conduction rate
-high resistance to fatigue
(medium speed/strength/endurance)

Question 37

Describe the properties of type IIb

Answer 37

-fast oxidative glycolytic
-fast fatigue resistant and medium sized motor unit
-fast conduction rate
-low resistance to fatigue
(good for strength/speed)

Fast twitch in power based muscles that require fast contractions, e.g. rectus femoris and levator palperbrae superloris.

Question 38

Compare the proportion of fibres in sprinters and long distance runners

Answer 38

Sprinters require a higher proportion of fast fibres, whereas long-distance runners require a higher proportion of slow twitch fibres.

Question 39

What does muscle strength correlate to?

Answer 39

Muscle strength directly correlates with the cross-sectional area of the muscle and is also governed by synchronisation of motor unit recruitment.

Question 40

Define ‘atrophy’

Answer 40

Decrease in muscle fibre size resulting from a lack of stimulation.

Decreased rate of protein synthesis, increased rate of protein degredation

Question 41

Give reasons for potential muscle weakness

Answer 41

-Lack of use
-Neurological disruption
-Bed rest
-Splinting
-Non-weight bearing
-Pathology
-Aging
-Malnutrition

Question 42

Describe the relative atrophy of type 1 and 2 fibres

Answer 42

Type 1fibres atrophy to a greater extent than type 2
Deep regions of oxidative slow twitch atrophy more
Largest muscles tend to atrophy the most irrespective of fibre type

Question 43

How is atrophy prevented?

Answer 43

Increased muscle tension/effort
Increased loading
Resisted exercise
…all increase protein synthesis.

Question 44

Describe muscle hypertrophy

Answer 44

• Muscle increases in size and strength
• Increase in cross sectional area of the muscle fibres
• Increase in the connective tissue
• Alteration of fibre type
• Alteration in metabolic capacity of the muscle
• Alteration in myosin heavy-chain isoforms
• Increase capillary density, myoglobin content, enzyme activity of mitochondrial and oxidative power

Question 45

Define muscle ‘strength’

Answer 45

Strength is the ability of a muscle (or group of muscles) to produce tension and a resulting force in one maximal effort, either dynamically or statically, in relation to the demands placed upon it.

Question 46

Describe the physiological processes involved in strengthening

Answer 46

• Increased actin and myosin filaments
• Causes thickening of myofibrils
• Causes increased myocytes and sacromeres
• Increased mitochondria so more efficient use of ATP, glycogen and phosphocreatine
• Increased vascularisation of muscles, increased supply of oxygen, carbon dioxide and waste moves out

Question 47

Define ‘power’

Answer 47

Power is the achievement of work in a given time period. Determined by the strength of contraction and distance moved in a specified time.

Question 48

Define ‘endurance’

Answer 48

Endurance is the ability to contract repeatedly or to sustain tension over a prolonged period of time

Question 49

Give the principles of increasing muscle strength, power and endurance

Answer 49

Overload  Specificity  Individuality  Motivation  Learning  Diminishing returns  Reversibility

Question 50

Describe progressive overload

Answer 50

In order to strengthen muscle, it must be taxed to the point of fatigue.
Intensity needs to be 60% of the Maximum Voluntary Contraction (MVC)
Some regimes were designed to objectively chart progress, some targeting power gains, other endurance.
Whichever is selected, it must be performed regularly, with the resistance being increased to maintain overload.
Resistance can be offered by: dead weights +/- body weight, pulley weights, springs & theraband.

Question 51

Describe the optimal intensity of strengthening exercises

Answer 51

American college of sports medicine ◦ 8-12 RM
Optimum frequency 3 times a week – minimum twice a week
Normally start slowly with low intensity of exercise
UL 30 -40% of 1RM, LL 50 -60% of 1RM once able to complete a set of 12 increase by 5%
Progression of weight every 1-2 weeks or if elderly 2-4 weeks

Question 52

Describe the principle of specificity

Answer 52

Different types of exercise produce different effects, therefore the regime must be specific to the requirements of the individual, either sports specific or functional needs. Training does not transfer between types of contraction, range of contraction, types of muscle fibre and therefore activities.
Eccentric muscle contraction appears to be effective and efficient increasing muscle strength. If movement is not possible due to pathology isometric exercises will improve isometric strength and enhance isotonic strength when movement is allowed. Speed of isotonic contractions can effect strength changes. The speed the muscle needs to contract for a specific functional task is the ideal speed of the exercise.

Question 53

Describe the principle of reversibility

Answer 53

Unless muscle is constantly used, strength gains will be lost. Even highly trained athletes lose the effects of years of exercise. Use it or lose it.

Question 54

Describe the principle of individuality

Answer 54

Each individual responds differently to exercises due to differences in muscle, metabolism, endocrine, genetics etc.

Question 55

Describe the principle of motivation

Answer 55

Physical and mental motivation is required to ensure patient compliance with treatment

Question 56

Describe the principle of learning

Answer 56

Enough time to both learn and understand the exercise

Question 57

Describe the principle of diminising returns

Answer 57

Exercise regime produces greater strength improvement in those with poor fitness/strength than healthy.

Question 58

Describe the factors behind muscle strength

Answer 58

Type of contraction
Frequency of firing of motor units
Psychological factros
Angle of pull
CSA of muscle
Age and fitness
Length/tension relationship
Neural factors
Length of lever arm
Strength and stiffness of connective tissues
Speed of contraction
Genetics
Number of motor units activated

Question 59

Describe the oxford scale for measuring grading muscle strength

Answer 59

0 = no contraction
1 = flicker (either observed or palpated)
2 = full range of movement with gravity counterbalanced
3 = full range of movement against gravity and with a hold
4 = full range of movement against gravity with a minimal resistance
5 = full range of movement against a maximal resistance

Question 60

How is strength measured?

Answer 60

Circumferential measurement is an indicator of atrophy, but due to the length of time required to re-establish muscle mass, is not a good indicator of strength gains.
Dynamometers, either isokinetic (Cybex, Biotex) or hand held.

Question 61

Describe newtons 1st law

Answer 61

‘Every object will remain at rest or with uniform velocity unless acted upon by an unbalanced force.’ Inertia = reluctance of a body to change what it is doing.
The greater the mass, the greater the inertia. Grade 1& 2 muscles may have insufficient strength to overcome inertia.

Question 62

Describe newtons second law

Answer 62

‘When a force acts on a body, the change in motion experienced by the body takes place in the direction of the force, is proportional to the size of the force and for the duration the force acts”.
Gravity and change of momentum affect both laws 1 and 2 so can be used in strengthening exercises.