Resistance Exercise

Muscle performance

  • Definition: Ability of muscle to do work, defined as:
      - Formula: Force ( \times ) Distance

  • Influences: Complex functional movement influenced by various body systems.

  • Key Elements:
      - Strength: The ability to exert force.
      - Power: The ability to exert force quickly.
      - Endurance: The ability to perform an activity over an extended period.

Resistance exercise

  • Definition: Dynamic or static muscle contraction resisted by an outside force either applied mechanically or manually.

Strength

  • Definition: Extent to which contractile elements of muscle can produce force.

  • Measurement: Greatest measurable force exerted by a muscle or muscle group to overcome resistance during a single maximum effort.

  • Functional Strength: Production of appropriate force to perform functional activities smoothly and in a coordinated manner.

Strength training

  • Definition: Systematic practice of using muscle forces to raise, lower, or control heavy external loads for a low number of repetitions over a short period.

  • Common Adaptation: Increase in maximum force-producing capacity of muscle.

Power

  • Relation: Related to strength and speed of movement.

  • Calculation: ( \text{Power} = \frac{\text{Force} \times \text{Distance}}{\text{Time}} )

  • Types of Activities:
      - Single bursts of high-intensity activity (e.g., lifting heavy luggage).
      - Repeated bursts of less intense activity (e.g., climbing stairs).

Power training

  • Goal: Achieve power by increasing the work a muscle performs during a specific time period or by reducing the time required to produce the work.

  • Example: Plyometric exercises – involve high intensity, such as jumping up and slowly lowering down.

Endurance

  • Definition: Ability to perform repetitive or sustained activities over a prolonged period.

  • Types:
      - Cardiopulmonary Endurance: Related to whole-body repetitive dynamic motor activities (e.g., running, cycling, swimming).
      - Muscle Endurance: Ability of a muscle to contract repeatedly against an external load, generate and sustain tension, and resist fatigue over time.

Endurance training

  • Definition: Systematic practice of using muscle force to raise, lower, or control a light external load for many repetitions over an extended time.

  • Adaptations: Muscles increase oxidative and metabolic capacities.

  • Benefits for Impaired Patients: Endurance training may be the most beneficial.

Benefits for resistance exercise

  • Enhanced muscle performance.

  • Increased strength of connective tissue.

  • Greater bone mineral density (began as exercise for osteoporosis patients).

  • Reduced risk of soft tissue injury.

  • Improvement in ability to heal and repair damaged soft tissue (remodeling).

  • Improvement in balance.

  • Enhanced physical performance.

  • Positive changes in body composition.

  • Feeling of well-being.

  • Improvement in perception of disability and quality of life (QOL).

Overload principle

  • Definition: To improve muscle performance, resistance loads must exceed the metabolic capacity of the muscle.
      - The muscle must be challenged to perform at a greater level than what it is accustomed to in order to see gains, grow, and strengthen.

  • Safety Considerations:
      - Load must be applied in context of the patient's underlying pathology, age, stage of tissue healing, patient response, and overall abilities.
      - If it's not going to challenge them, it is not going to change them!

Specific Adaptation Imposed Demands (SAID) Principle

  • Definition: The adaptive effects of training are highly specific to the training method employed.

  • Concept: Extension of Wolff’s law:
      - Strength training will increase strength.
      - Endurance training will increase endurance.

  • Exercise Specificity: When possible, exercises should mimic anticipated function. Task-specific practice should always be emphasized.

  • Overflow Training: Suggests a cross-training effect in non-trained muscle when the contralateral limb is exercised.

Detraining

  • Patient Consideration: Patients may want to maintain involvement in a maintenance program.

  • Decline of Effects: The effects of training can begin to decrease as early as 1-2 weeks following cessation of all exercises.

  • Advice for Patients: Encourage continuation of exercises even after perceived improvement or completion of therapy.

Factors that influence Tension Generation

  • Energy stores and blood supply.

  • Fatigue (both local and whole-body).

  • Underlying pathology (e.g., adhesive capsulitis, rotator cuff tear, torn quadriceps).

  • Impairments (e.g., decreased range of motion, strength, balance).

  • The stage of healing (acute, subacute, chronic).

  • Patient's age and overall fitness level.

  • Psychological and cognitive factors.

Physiological Adaptations to Resistance Exercise

  • Neural Adaptations: Occur first, within 4 weeks, characterized by an increase in EMG activity with little or no hypertrophy yet. This includes increased motor learning and improved coordination.

  • Skeletal Muscle:
      - Hypertrophy: Occurs at approximately 6-8 weeks, with increased muscle size due to increased actin and myosin synthesis and decreased protein degradation.
      - Greatest Increases: Observed with eccentric training.

  • Vascular and Metabolic: Characterized by a reduction in capillary bed density and a decrease in mitochondrial density.

  • Connective Tissue: Increased tendon and ligament strength, thickening of connective tissue in muscle, and increased bone mineral density.

Determinants of Resistance Program

  • Key Factors:
      - Alignment
      - Stabilization
      - Intensity
      - Volume
      - Exercise order
      - Frequency
      - Rest interval
      - Duration (for both single sessions and over weeks)
      - Mode
      - Velocity
      - Periodization
      - Integration into functional activities.

Alignment and Stabilization

Alignment

  • Considerations: Fiber orientation, line of pull, specific action of the muscle.

  • Replicating Muscle Action: Patient must be positioned so that gravity provides resistance to the muscle being strengthened.

  • Example: Strengthening gluteus medius – sidelying position for maximum benefit.

Stabilization

  • Definition: Holding the body steady, essential for proper alignment and avoiding substitution or compensation.

  • Practices: Exercising on a firm surface;
      - External Stabilization: Provided by therapists, belts, straps, or gravity.
      - Internal Stabilization: Achieved through isometric contraction of adjacent muscle groups.

Exercise Intensity

  • Definition: The amount of external resistance imposed on contracting muscles during each repetition.

  • Common Terms: Also referred to as exercise load.

  • Types of Loads:
      - Submaximal vs. Maximal Loads:
        - Consider goals and expected outcomes, the cause and extent of muscle deficits, stage of healing, patient’s age, general health, and fitness level.
      - Resistance exercises causing pain indicate too much intensity.

Repetition Maximum (RM)

  • Definition: A method to determine appropriate exercise load.

  • 1-RM: Greatest amount of weight that can be moved with control through the full range of motion (ROM). Requires trial and error due to safety considerations.
      - Resource: See ( www.strengthlevel.com ) for estimates of 1-RM.

Training Zone

  • Definition: After determining 1-RM, amount of weight used for exercises is calculated as a percentage of the RM.
      - Start: Beginning of the program should begin with 30-40% RM.
      - Advanced Users: Highly trained individuals can use 70-80% RM.
      - Recommendation: Exercising at low to moderate percentages of RM is recommended for children and elderly patients.

Exercise Volume

  • Definition: Summation of total repetitions and sets.

  • Inverse Relationship: Between repetitions and volume.

Repetitions

  • Definition: Number of times the movement is performed consecutively.

  • Determining Factors: Depends on strength vs endurance needs.

Sets

  • Definition: Predetermined number of consecutive repetitions grouped together.

  • Common Practice: 2-4 sets is the most common recommendation with brief rest between sets.

Dosing Example

  • Novice: 60% 1-RM, 3 days per week, 4 sets of 8-12 reps.

  • Intermediate: 80% 1-RM, 2 days per week, 4 sets of 4-6 reps.

  • Advanced: 85% 1-RM, 2 days per week, 8 sets of 2-4 reps.

  • Duration: Specifications for how long should be determined.

Exercise Order

  • Significance: Sequence of exercises has a direct impact on fatigue and adaptive training effects.

  • Recommendations: Large muscle groups should be trained before small muscle groups. Multi-joint exercises should be performed before single joint exercises. Higher intensity exercises should be performed before lower intensity exercises.

Exercise Frequency

  • Definition: Number of exercise sessions per day or week.

  • Determinants:
      - Intensity
      - Volume
      - Patient goals
      - General health
      - Previous participation in resistance programs
      - Response to training

  • Considerations: Eccentric exercises should be performed less frequently due to increased recovery time (DOMS).

  • Practice Duration: Initially, exercise programs are short and can be performed daily or multiple times a day. As intensity and volume increase, frequency typically decreases.
      - Generally, 2-3 times/week is recommended.
      - A rest interval of at least 48 hours for major muscle groups trained is advised (e.g., quads and hamstrings).

Exercise Duration

  • Definition: Total number of weeks or months a resistance program is carried out.

  • Variation: Depending on muscle deficits, some patients may require 1-2 months of resistance training to return to function; others may require continuous resistance training for life.

  • Significant Changes: Typically require at least 6-12 weeks of resistance training to manifest.

Rest Interval

  • Purpose: Allows muscles to recover.

  • Dependent Factors: Tied to the intensity and volume of exercise.

  • Recommendations:
      - For moderate-intensity exercises, a 2–3-minute rest period after each set is recommended.
      - Shorter breaks for lower intensity exercises; longer breaks for higher intensity.
      - Active recovery is more effective than passive recovery for neutralizing effects of muscle fatigue (e.g., training opposite limb or low-intensity cardio).
      - 48-hour rest intervals between sessions for major muscle groups are recommended.

Mode of Exercise

  • Definition: Refers to the form of exercise, the type of muscle contraction, and the manner in which the exercise is performed.

  • Types of Exercise:
      - Dynamic vs static
      - Isometric vs isotonic
      - Concentric vs eccentric
      - Weight bearing vs non-weight bearing
      - Goals can be strength, power, or endurance focused.
      - Types of resistance include manual vs mechanical and body weight vs external resistance.
      - Aerobic vs anaerobic considerations.
      - Short arc vs full arc (partial ROM vs full ROM).

Velocity of Exercise

  • Definition: Velocity of contraction impacts the tension produced by muscles, affecting strength and power.

  • Training Recommendations:
      - Training with free weights should be performed at slow to medium velocities.
      - Functional activities may require higher velocities.
      - Integrate plyometric training when safe.

Periodization and Variation of Training

  • Definition: Periodization was developed for highly trained athletes.

  • Goal: To progress training programs, prevent overtraining and burnout, and optimize performance during competition.

  • Methodology: Breaks the training calendar into cycles or phases, lasting weeks or months.

  • Variability: Varies in terms of exercise intensity, volume, frequency, and rest.

  • Evidence of Efficacy: Limited support is available for periodization efficacy in non-athlete populations.

Types of Resistance Exercise

  • Manual Resistance: Provided by a therapist; useful for early stages of rehabilitation.

  • Mechanical Resistance: Involves using equipment such as weights, thera-bands, machines, etc.

Isometric Exercise

  • Definition: Muscle contraction occurs without a change in length or visible joint movement.

  • Method:
      - Repetitive isometric contractions (20 repetitions of 6 seconds each) held with maximal effort have been shown to increase isometric strength.
      - Functional activities require stabilization (isometric hold) of one body segment while another moves.

  • Postural Muscles: Provide stability for balance and functional movements.

  • Sources of Resistance for Isometrics:
      - Holding against an applied manual force.
      - Holding a weight in a particular position.
      - Maintaining a position against body weight.
      - Pushing or pulling an immovable object.

  • Types of Isometrics:
      - Muscle-setting exercises.
      - Stabilization exercises.
      - Multiple-angle isometrics.

  • Precaution: Avoid the Valsalva maneuver (holding breath to build intra-abdominal pressure). Encourage patients to talk during the exercise to avoid this maneuver.

Concentric and Eccentric Exercise:

  • Concentric exercises involve muscle shortening as it contracts, which occurs during activities like lifting weights.

  • Eccentric exercises involve muscle lengthening while under tension, typically occurring during activities like lowering weights.

  • Definition: Both types are dynamic and used in functional, daily activities.

  • Load Control: Greater loads can be controlled with eccentric exercise; it's easier to lower a heavy weight than to lift it.

  • Strength Gains: Gains in muscle strength and mass are greater with max-effort eccentric training than concentric.

  • Metabolic Efficiency: Eccentric muscle contractions are metabolically more efficient and generate less fatigue than concentric contractions.

  • Patient Consideration: It may be easier for weak patients to lower limbs than to raise them.

  • DOMS: Following unaccustomed, high-intensity eccentric exercises, there is greater incidence of delayed onset muscle soreness (DOMS).

  • Cross-Training Effect: Both types have a cross-training (overflow) effect on contralateral muscles.

Constant and Variable Resistance

Constant External Resistance

  • Description: Involves free weights, cuff weights, weight machines, or pulley systems.

  • Consideration: The contracting muscle is challenged maximally at only one point in the range of motion due to the length-tension relationship.

  • Impact: Major component of rehabilitation and fitness programs with documented gains in muscle performance.

Variable Resistance

  • Description: Specifically designed resistance equipment varies the level of resistance throughout the range of motion.

  • Examples: Gym equipment such as Cybex and Nautilus machines, therabands.

Open and Closed Chain Exercise

  • Open Chain Exercise: Involves the movement of a distal segment (e.g., arms or legs) while the other end is free, which allows for greater isolation of specific muscle groups.

  • Closed Chain Exercise: Involves the movement of a distal segment while the other end is fixed or in contact with a surface, promoting joint stability and functional strength.

Open Chain Exercise

  • Characteristics:
      - Distal segment moves in space.
      - Independent joint movement.
      - Muscle activation primarily in prime mover only.
      - Non-weight bearing (NWB).
      - Resistance applied to a moving segment.
      - External stabilization often required.

Closed Chain Exercise

  • Characteristics:
      - Distal segment remains fixed.
      - Interdependent joint movement.
      - Multiple muscle groups activated.
      - Weight bearing (WB).
      - Resistance applied to multiple moving segments.
      - Internal stabilization achieved through postural control.

Closed Chain Exercises

  • Benefits:
      - Provide more joint approximation through weight-bearing.
      - Stimulate co-contraction of agonist and antagonist muscles, using more muscle groups simultaneously.
      - Greater proprioceptive and kinesthetic feedback.
      - Improve balance and postural control.

Precautions for Resistance Training

  • Concerns:
      - Valsalva maneuver (may cause increased blood pressure).
      - Hints to Avoid Valsalva: Do not hold breath, exhale during motions, ask the patient to count.
      - Substitute motions or compensation.
      - Overtraining and fatigue (both acute and delayed muscle soreness).
      - Gradually increase intensity, warm up and cool down adequately, stretch before and after exercises.
      - Risks of pathological fractures (especially with osteoporosis).

Contraindications to Resistance Exercise

  • Contraindications:
      - Pain (acute).
      - Inflammation.
      - Severe cardiopulmonary disease.

Proprioceptive Neuromuscular Facilitation

  • Technique: Proprioceptive Neuromuscular Facilitation (PNF) can be applied to develop muscular strength and endurance.

  • Goals: Facilitate stability, mobility, neuromuscular control, and coordinated movements through diagonal patterns (D1 and D2) for both upper and lower extremities.

Equipment for Resistance Exercise

Equipment Types

  • Free Weights

  • Theraband

  • Simple Pulley Systems

  • Variable Resistance Units

  • Body Weight Exercises
      - Incorporates ( 7 \text{ Daily Moves} ) - Refer to free application ( www.7dailymoves.com )

  • Physio Balls and Medicine Balls

  • Body Blade

  • Slide Boards

  • Aerobic Machines (e.g., StairMaster)