Strength Training & Muscle Contractions

• Strength training can be classified according to different variables:
• Methods of work
• Istonic vs isokinetic
• Open vs closed-chain exercises
• The arc of motion
• Types of resistance

Types of Muscle Contraction

• Motor moment = resistant movement results in an isometric contraction
• Motor moment > resistant movement results in a concentric contraction
• Motor moment < resistant movement results in an eccentric contraction

Isometric Considerations

• Resistance is variable and accommodating
• Adaptive changes in the muscle occur when contractions are held for at least 6 seconds
• Strengthening of muscles is developed at a point in the ROM, not over the entire length of the muscle
• This type of resistance exercise can increase blood pressure
• Use cautiously with patients with a cardiac condition
• Monitor for potential Valsalva maneuver

Concentric vs Eccentric Considerations

• Maximum eccentric contraction produces more force than maximal concentric contraction
• Resistance training performed concentrically improves concentric muscle strength
• Eccentric training improves eccentric muscle strength (specificity of training)
• Eccentric contractions occur in a wide variety of functional activities, such as lowering the body against gravity, e.g., sitting down or descending stairs
• Eccentric contractions provide a source of shock absorption during closed-chain functional activities
• Eccentric contractions consume less oxygen and fewer energy stores than concentric contractions against similar loads

Isometric Advantages

• Static contraction allows muscle activity in cases where articular movement is forbidden, for example, plaster cast immobilization
• Allows muscle strengthening while preventing articular problems, for example in cases of painful articular friction
• Allows conservation of body image when movement is not allowed, and that is through activation of the neuromuscular image
• Allows the mobilization of muscle elements without any linear motion and consequently, it prevents the adherence of the tendon in its gain in cases of immobilization
• Allows maintaining cartilage trophicity through modification at the articular level

Isotonic Advantages

• Allows the recuperation of the range of motion
• Allows the maintenance and gain of body image by activation of the neuromuscular system
• Allows the maintenance and gain of spatial image, and that by increasing the afferents from capsules and articular ligaments

Isometric Disadvantages

• Static contraction cannot provoke gliding of the articular surface
• Does not allow the restoration of spatial image (image in relation to the displacement of segments in the environment) due to the absence of capsulo-ligamentary tension
• Does not allow for doing known tasks, thus execution is not easy

Isotonic Disadvantages

• Causes friction and axial compression on articular surfaces that might aggravate the pathological articular conditions

Isometric Application Modalities

• When the subject maintains the determined joint activity against gravity
• When the subject maintains an attitude, when performing a given task, against direct or indirect charge
• When the manual resistance of the therapist or the auto-resistance of the patient balances the motor moment
• When a muscle or group of muscles contracts against a fixed object
• When two antagonist muscles contract at the same time (co-contraction)

Isotonic Classifications

• Pure active
• Pure rhythmic
• Active-passive or active assisted: Supported active, Directed active
• Active in water: N.B.
• Active under traction: N.B.
• Active with stretching: supplementary contraction
• Active against resistance: N.B.

Types of Resistance

• Resistance can be manual or mechanical

Manual Resistance

• A type of active exercise in which another person provides resistance

Mechanical resistance

• A type of active exercise in which resistance is applied through the use of equipment or mechanical apparatus

Manual Resistance Advantages

• Useful in the early stages of an exercise program when the muscle is weak
• Therapist can judge the capability of the muscle to safely meet the demands of exercise
• Can be modified for a painful arc in the joint range of motion
• Safe resistance exercise when the joint movement needs to be carefully controlled and the resistance is mild to moderate
• Can be easily changed to include diagonal or functional patterns of movement (e.g. PNF) or appropriate facilitation techniques (e.g. quick stretch)

Mechanical Resistance Advantages

• The amount of resistance can be measured quantitatively and increased over time
• Can be used when the amount of resistance is greater than the therapist can apply manually

Manual Resistance Disadvantages

• The amount of resistance cannot be measured quantitatively
• The amount of resistance is limited by the strength of the therapist or caregiver
• It may be difficult to maintain the same resistance during the full joint range of motion and to consistently repeat the same resistance

Mechanical Resistance Disadvantages

• Not easily modified to exercise in diagonal or functional patterns
• It may not be safe if resistance needs to be carefully controlled or maintained at low levels

Arc of Motion

• Short arc exercise: Resistance exercise performed through a limited ROM, e.g., initial exercise post knee surgery (anterior cruciate repair), painful full range movement
• Full arc exercise: Resistance exercise performed through full ROM

Open vs Closed-Chain Exercise Kinematics

• Open (distal segment moves freely):

• Open-chain exercise occurs when the distal segment (hand or foot) moves freely in space; e.g., when an arm lifts or lowers a handheld weight

• Independent joint movement; no predictable joint motion in adjacent joints

• Movement of body segments only distal to the moving joint

• Muscle activation occurs predominantly in the prime mover and is isolated to muscles of the moving joint

• Typically performed in non-weight-bearing positions

• Resistance is applied to the moving distal segment

• Use of external rotary loading

• External stabilization (manually or with equipment) is usually required

• Whatever the type of movement faced, the direction of recruitment of synergistic muscles in the open kinetic chain is always proximodistal

• Remember this when choosing chains to work weak muscles distally in an open kinetic chain

• Closed: (body moves over fixed distal segment)

• Closed-chain exercise occurs when the body moves over a fixed distal segment; e.g., stair climbing or squatting activities

• Interdependent joint movements; relatively predictable movement patterns in adjacent joints

• Movement of body segments may occur distal and/or proximal to the moving joint

• Muscle activation occurs in multiple muscle groups, both distal and proximal to the moving joint

• Typically, but not always, performed in weight-bearing positions

• Resistance is applied simultaneously to multiple moving segments

• Use of axial loading

• Internal stabilization by means of muscle action, joint compression, and congruency and postural control

• If weight bearing is not included, use OKC, not CKC

• Preparing the patient for functional weight bearing requires Closed Kinetic Chain → CKC

• CKC loads muscles, bones, joints, and noncontractile soft tissues such as ligaments, tendons, and joint capsules → mechanoreceptors are stimulated → joint stability, balance, coordination

Isotonic vs Isokinetic

• Resistance for isotonic is constant (free weights, classical weight machine, pulley system) or Variable (special machine)
• Resistance for isokinetic is accommodating and variable
• Muscle work can be reached by two complementary methods of work:
• Selective method → analytical techniques & global techniques
• Functional methods

Analytical Techniques

• The analytical techniques realize a precise work for a muscle or group of muscles having a generally common function
• The articular starting and end positions are specified in a way to put non-needed muscles in a position of no or least function
• The executed movement is simple, well-determined, and generally monoarticular
• Analytical techniques demand localized muscle contraction only at the level of weak muscles
• All modes of resistance are applicable for this type of work, but the manual resistance is the privileged instrument for better guide and dosage of contraction
• Note that the resistant moment must not cross a certain limit in order to eliminate any recruitment of other muscles

Global Techniques

• The global techniques realize fine movements through the intervention of muscles having different functions
• Depends on the muscles whose activity provokes that of others or reinforces their contractions
• The chosen muscle to provoke contraction is called GACHETTE
• The muscle that aim to work by contracting GACHETTE muscles is called CIBLE
• The executed movement is combined, helps restore activities of daily living, and is generally polyarticular
• The global technique seeks contraction of all muscles of the kinetic motor chain
• All modes of resistance are applicable for this type of work, but if the opposing resistance is manual, the PT can modulate their resistance in a sector more than another in the motor chain
• Consequently helps work the needed muscle in a defined muscle course

Types of Global Techniques

• Polyarticular movement: for example, triple flexion or extension of lower limbs
• Proprioceptive neuro-muscular facilitation (PNF): example, Kabat, Bobath, Brunnstrom, Temple Fay, Rood
• Equilibrium and stabilization: The reflexes of equilibration, balance, and stabilization provoke muscle contractions:
• Search for a fixed point in order to give for the motor moment a good efficiency
• Split a part of the body in order to conserve the line of gravity in the polygon of the base of support

Functional Methods

• Functional methods are opposite to selective methods in that they do not have as their objective the education of an isolated task or movement at the level of the arthroligamentous or musculotendinous system
• Restores to the patient its real functional capacities: precise, harmonious, economic, and adapted tasks

Fundamental Principles of Gymnic Therapeutic Exercises

• Mobilize body segments slowly, and that by reducing to a minimum the acceleration
• Allow the muscles to contract all the way through the range of motion
• Maintain the alignment of body segments, as any change in the alignment will change the angle of action of the muscles as well as the length of muscles, tendons, and ligaments
• Maintain balance of antagonist muscle groups; for example, if the exercise aims to strengthen the biceps, we must also conduct exercises to strengthen triceps
• Use one or several groups of exercises to improve and maintain the integrity of all structures and tissues in relation to the injured part i.e, the joints proximal and distal to the lesion site
• Develop alternative exercises to reduce the monotony of the exercise and ensure variability Maintain and develop aerobic capacity

Progression of Exercise

• A good and planned progression ensures the recovery of the injured body part to the highest possible level of function and with the shortest duration possible

Progression Techniques

• The change in the starting position
• The change in the base of support of the initial or starting position
• The change in the surface on which exercise is executed
• Increase the time to perform a given exercise
• The progression of resistance
• The change of the lever arm
• The Range of Motion
• The Change in the Starting Position affects the muscular function in performing a certain movement
• If the gravity is counterbalanced, the muscle work will be easier than if the gravity resists the movement
• For example, if the patient is lying on the floor, during abduction of the shoulders, the abductors work less than if the patient performs the same movement in a sitting position
• A wide base (standing position with lower limbs apart) ensures more stability than a narrow base of support, lower limbs joined together, or standing on toes
• Performing exercise on a stable surface (ground) is easier than exercise done on an unstable surface
• Measures can control the time of performance of each exercise or by counting repetitions
• The total duration must be increased gradually, for example, from 20 min to 30 min per day, then 45 min till reaching 1 hour
• Duration depends upon the needs of the patient and the style of life the patient wants to regain
• The PT must introduce the weights or resistance in appropriate exercises to offer resistance greater than the weight of the limb
• Without this increase, the exercises should be repeated by a non unacceptable number of repetitions to reach the desired momentary fatigue
• The resistance must be progressive according to the potential of the patient
• The muscle works more easily in the mean range of motion in which functional movements are performed
• Thus, weak muscles must be reeducated in this mean range, and progress for more difficult exercises towards the rest of the range
• A short lever arm is easier to mobilize than a long one
• In working back extensors in the prone position, start with the upper limbs along the trunk, and then to make the exercise heavier and more difficult, increase the lever arm by extending the two upper limbs
• Velocity can be reduced or increased according to desired progression
• Walking can be made more difficult by reducing the speed of walking which necessitates increased need for stability
• Throwing a ball against the wall seems more difficult if performed more rapidly, as it necessitates more coordination and the muscle action is more rapid
• The original exercise program must be written and progressed systematically each session according to patient ability
• Exercises can be progressed and changed according to the patient ability if the patient shows good understanding and performance

Application Modalities

• Group exercise is helpful in cases of light static disorders and is more dynamic and less monotone than individual exercise
• Individual Exercise is helpful in pathological cases and necessitates the presence of a qualified physical therapist

DeLorme and Watkins (Dynamic Method)

• HRE, the charge must be direct and progressively increased: 10RM
• 3 sets (10 repetitions/set)
• First set with 1/2 of 10 RM
• Second set with 3/4 of 10 RM
• Third set with 10RM
• Session is 5 minutes
• 4 sessions per week
• The 10RM is retested or recalculated each week

DOTTE (Dynamic Method)

• Direct Progressive Method
• RM
• 3 sets (10 repetitions/set)
• Charge must be direct and progressively increased:
• First set with 2/5 of 1RM
• Second set with 3/5 of 1 RM
• Third set with 4/5 of 1RM
• Session 5 minutes

Rocher (Dynamic Method)

• A charge is indirect and progressively increasing
• R: By dynamometer, ex: static contraction
• 2 sets (20/first set and 10/second set)

Mac Gover et Luscombe (Dynamic Method)

• Used the method of decreasing progressive resistance
• The protocol is similar to DeLorme and Watkins
• First set with 10RM
• Second set with3/4 of 10RM
• Third set with 1/2 of 10RM

Oxford Technique de Zinovieff (Dynamic Method)

• Used a method of progressively decreasing resistance
• 10 RM
• 10 sets (10 repetitions/set)
• 1st set with 10Rm
• 2nd set with 90% of 10RM
• 3rd set with 80% of 10RM
• 4th set with 70% of 10RM
• 10th set with 10% of 10RM
• 5 sessions per week

Macqueen (Dynamic Method)

• The charge used is direct and constant
• 10 RM
• 4 sets (10 repetitions/set)

Method of Troisier (Static Method)

• Troisier proposed the intermittent static exercise
• He seeks the maximal force of the patient in static mode and determines the imposed charge as follows:
• Evaluate the maximal measured force (MMF) by three trials separated by a one-minute rest to choose the highest value, then calculate the maximal theoretical force (MTF), by adding 25% to the (MMF)
• Thus, MTF=MMF+25% MMF
• Then calculate the imposed charge ( f) equal to 50% MTF;
• Thus f = MTF/2 = (MMF + 25% MMF)/2
• The session is composed of 50 repetitions
• Session 5 minutes of effective training (6 seconds followed by 6 seconds of rest)

Method de Hettinger et Muller (Static Method)

• Proposed the use of isometric contractions to prevent muscle atrophy
• The contraction must use at least 50% of the maximum of muscle force
• The session is composed of 3 contractions
• Each contraction lasts 6 seconds
• 1 session per day, and 5 sessions per week

Circuit Weight Training

• A sequence of exercises for total-body conditioning
• A rest period of usually 30 seconds to 1 minute is taken between each exercise
• Exercises can be done with free weights or weight training machines

Plyometric Training or Stretch-Shortening Activity

• An isotonic exercise that combines speed, strength, and functional activities and is used in later stages of rehabilitation to achieve a high level of performance
• Example: jumping off of a platform, then up onto the platform at a rapid pace to improve vertical jumping abilities

Brief Repetitive Isometric Exercise

• Occurs with up to 20 maximum contractions held for 5 to 6 seconds and performed daily
• A 20-second rest after each contraction is recommended to prevent increases in blood pressure
• Strength gains occur in 6 weeks

Goals and Indications for Resistance Exercise

• Increase strength as a muscle group that lifts, lowers, or controls heavy loads for a relatively low number of repetitions
• Increase muscular endurance by performing low-intensity repetitive exercise over a prolonged period of time
• Improve muscular performance related to strength and speed of movement

Precautions: Local Muscle Fatigue

• Resulted from repeated dynamic or static contractions over a period of time
• Caused by:
• Depleted energy stores
• Insufficient oxygen
• Build-up of lactic acid
• Characterized by:
• A decline in peak torque
• Increased muscle pain with occasional spasms
• Decreased AROM

General Muscle Fatigue

• Affects the whole body after prolonged activities such as walking or jogging
• Caused by:
• Low blood sugar
• Decreased glycogen stores in muscle and liver
• Depletion of potassium

Fatigue

• May be linked to specific clinical diseases:
• Multiple sclerosis
• Cardiac disease
• Peripheral vascular dysfunction
• Pulmonary diseases
• These patients fatigue more rapidly and require longer rest periods
• Overwork will result in temporary or permanent loss of strength

Fatigue in Normal Individuals

• Vigorous resistance training and fatigue causes discomfort however, overtraining and muscle weakness don't usually occur

Fatigue in Patients

• Patients with lower motor neuron disease e.g., post-polio syndrome undergoing vigorous resistance training results in deterioration of strength
• Overwork can be avoided with slow progression of the exercise intensity, duration and progression

Osteoporosis

• Prolonged immobilization, bed rest, and the inability to bear weight on an extremity can cause a nutritional or hormonal factor
• Makes the bone unable to withstand normal stresses and highly susceptible to pathological fracture

Acute Muscle Soreness

• Decreased blood flow and reduced oxygen
• Accumulation of H+
• Lactic acid and potassium
• Tissue edema
• Disappears within minutes or hours after exercise

Delayed Onset Muscle Soreness

• Caused by eccentric muscle contraction
• Muscle and connective tissue damage
• Inflammation (macrophages, white blood cells)
• Increased chemical mediators (bradykinin)
• Can begin 12 to 24 hours after a strenuous bout of exercise
• Peaks 24 to 48 hours after exercise
• Muscle tenderness and stiffness can last up to 5 to 7 days
• May be due to edema (accumulation of fluid) inside the muscle compartment

Armstrong's Sequence of Events in DOMS

• Structural damage → impaired calcium availability → accumulation of irritants → increased microphage activity

DOMS and Performance

• DOMS causes a reduction in the force-generating capacity of muscles
• Maximal force-generating capacity returns after days or weeks
• Muscle glycogen synthesis is impaired
• Stretch after exercise
• Ice after exercise
• Cool down after exercise (to prevent acute muscle soreness
• Gradual progression of exercise (to prevent DOMS) by controlling
• Resistance
• Repetitions
• Sets
• Rest between exercise bouts
• TENS, ultrasound, nutritional supplements, or acupuncture can help
• Solution: prevent occurrence through gradual adaptation to exercise
• Pre-conditioning of muscle: chronic yoga
• Gradual habituation to eccentric contractions

Inflammation

• Resistance exercises can increase swelling and cause damage to muscles or joints

Pain

• Severe joint or muscle pain during exercise or for more than 24 hours after exercise requires an elimination or reduction of the exercise