Strength Training: Introduction to Concepts

Strength Training: Introduction

• Strength training is synonymous with resistance training
• It involves muscles working against a load (weight or resistance)
• Examples of resistance include body weight, free weights, weight machines, and resistance bands
• Strength training is an anaerobic exercise, where energy production occurs without oxygen

Strength: Basic Concepts

• Strength is the ability of a muscle or muscle group to exert force against a load
• During strength exercise, force is generated by muscles
• The amount of resistance/weight applied to a movement determines the strength needed

Neuromuscular Capacity

• Neuromuscular capacity involves the ability to initiate, accelerate, decelerate, halt, and change the direction of a load within or outside the organism

Muscle Contraction

• Strength is produced through muscular contractions
• An action potential causes the muscle to either shorten, lengthen, or maintain its position in response to the load
• Three types of muscle contractions are concentric, eccentric and isometric

Muscular Contraction Production

• An action potential travels from neurons to the muscle fiber
• Acetylcholine (Ach) releases, depolarising the muscle fiber
• Calcium influx allows myosin heads to bind to actin and pull towards the M line
• This process creates muscular contraction

Local Factors Affecting Muscle Contraction

• Number of recruited motor units, and recruitment co-ordination
• Size of muscle (primarily fibre diameter) and connective tissue quality
• Muscle fibre type
• Muscle fibre orientation
• Contraction type
• Sarcomere length at initiation
• Fatigue: central and peripheral

Muscle Types and Properties

• Type I (red): slow oxidative, small diameter, aerobic, slow contraction, low strength, high aerobic capacity, low anaerobic capacity, high myoglobin, mitochondria and capillaries
• Type IIA: fast oxidative glycolytic, intermediate diameter, aerobic and glycolytic, quick contraction, high strength, mid aerobic capacity, low anaerobic capacity, mid myoglobin, mitochondria and capillaries
• Type IIB/X (white): fast glycolytic, large diameter, ATP-PC and glycolytic, quick contraction, high strength, low aerobic capacity, high anaerobic capacity, low myoglobin, mitochondria and capillaries

Muscle Contraction: Fatigue

• Central fatigue is a decrease in voluntary activation due to less frequency of motor neurons and decreased stimulus from the cortex
• Factors affecting central fatigue include sleep deprivation, task fatigue, anxiety, stress and serotonin increase, dopamine decrease
• Peripheral fatigue is reduced contractile strength of muscle fibers due to impaired cross-bridge action and metabolite accumulation
• Factors such as metabolite accumulation, ATP synthesis reduction, pyruvate and hydrogen increase, glycogen depletion and acidosis are linked to peripheral fatigue.

Motor Unit Recruitment Coordination

• Synchronized recruitment of motor units is essential to execute a muscle contraction
• Coordination between antagonists, agonists, and synergists is crucial for efficient and effective action
• Intramuscular coordination describes cooperation between different parts of the same muscle; intermuscular coordination occurs between different muscles.

Strength Exercise: Definitions

• Rep Max (RM): The maximum weight a person can lift with a given number of repetitions (e.g., 1RM, 5RM).
• Rate of Perceived Exertion (RPE): A measure of a person's exertion level.
• Repetitions in reserve (RIR): Remaining repetitions a person thinks they can do before failure.
• Character of Effort: Relationship between effort and movement velocity.

Strength: Definitions (continued)

• Maximum strength: The ability to produce the greatest force possible in a single action
• Muscular endurance: Ability of a muscle or muscle group to repeatedly contract against a resistance for a prolonged period of time.
• Muscle power: Ability to produce force in the shortest possible time
• Explosive strength: Maximum force a muscle can apply in a single contraction
• Reactive strength: Ability in changing an eccentric contraction to a concentric contraction during movement
• Hypertrophy: Enlargement of an organ due to an increase in cell size (e.g., muscle fiber).

Force/Velocity Relationship

• Eccentric contraction increases when force increases, concentric contraction velocity decreases when force increases, isometric contraction velocity equals 0
• This principle is shown graphically by a curve that represents force and velocity related

Power: Force and Velocity Relationship

• Power is the rate at which work is done (force x velocity)
• Peak power occurs at submaximal speed and load
• Power can be a determining factor in sporting performance and independence of the elderly who want to complete their daily activities

Explosive Strength and Rate of Force Development

• Time taken to reach required force is an important factor in explosive strength.
• The rate of force development is linked to muscle fibre type, neural drive and the stretch shortening cycle.

Adaptation in Response to Strength Exercise

• Changes in response to training program
• Factors which influence adaptation are frequency, intensity, time, type, and volume. If load lowered, adaptation may reverse to match requirements
• The body adapts by increasing capacity beyond initial level through repair and rebuilding processes, leading to enhanced strength and performance.
• Detraining: Reverse of adaptations due to training program reduction

Adaptation specific to Strength Training

• Muscle fiber adaptation to type IIa/type IIx
• Increased glycogen and PC reserves
• Increased enzyme activity for ATP synthesis
• Optimized motor unit and intermuscular coordination
• Efficient force transfer through connective tissue adaptation

Factors Affecting Adaptation: Frequency

• Training frequency must be optimized to allow for recovery while also pushing the body to maintain or advance performance
• Frequency can affect adaptation

Factors Affecting Adaptation: Intensity

• Intensity of exercise should be gradually increased, starting with very low intensity, with regard for individual circumstances
• High intensity for max strength; lower intensity for higher numbers of repetitions
• There are several methods for monitoring intensity including RPE and RIR

Factors Affecting Adaptation: Time

• Training time must be individualized based on goals, objectives, and time constraints
• The number of repetitions and sets should depend on the specific objectives to be met
• Speed of execution will depend on objectives

Factors Affecting Adaptation: Type/Muscle Group Selection

• Selecting the specific type of exercise to achieve particular adaptation results
• Concentric, eccentric, and isometric exercise must be considered.

Factors Affecting Adaptation: Volume

• The number of exercise sessions depends on the type of adaptation that is needed.
• Max strength usually requires fewer sets and reps, lower intensity, but greater strength for a shorter duration, while endurance requires higher numbers of sets, reps and lower intensity exercises over a prolonged period of time,

Factors Affecting Adaptation: Progression

• Overload is key to adaptation. Gradually increasing frequency, intensity, time, type or volume over a programmed period can lead to adaptation progression.
• Periodization is used to design training blocks to focus on specific qualities.

Strength Exercise: Prescribing in presence of MSK-related pain

• Exercise prescription must be tailored to the individual and their specific needs in terms of pain tolerance, experience, and condition.
• Pain should be a factored in and monitored to ensure it does not exceed the patient's ability to exercise without compromising their performance

Assessing Strength Exercise

• Functional: e.g., sit to stand, relevant to everyday tasks including functional independence
• Classification: e.g., Oxford Muscle Power—quick, inexpensive but does not truly quantify
• Quantifying: e.g., grip strength dynamometer—precise and reliable testing
• Common factors of strength assessment include warm-up and progressive sets to create a safe and appropriate experience.
• Direct and indirect approaches to measure max strength. Indirect assessments are estimations
• Grip strength: an important measure for multiple outcomes including hip fracture outcomes, and level of dependence.

Assessing Strength: Power

• Tests commonly combine power, reactive strength, and explosiveness
• Examples of assessments include long jump, vertical jump, hop distance, x3 hop distance, 6-m hope time, drop jump

Assessing Strength: Movement Analysis

• Assessment of movement quantity (reps, distance/time, fatigue)
• Measurement of movement quality, including identifying and addressing any limiting factors
• Movement analysis aids development of strength exercise programs that are focused and precise

Force-Velocity Profiling

• Used for performance testing in sports that require explosiveness, such as sprinting, high jump, or shot put.
• An athlete's force-velocity curve is obtained by measuring the force a person produces against various velocities
• This curve defines if the athlete is force or velocity dominant, which can be used to customise strength training programs

Assessing Strength: Muscular Endurance

• Assessing how long a contraction can be maintained or the amount of repetitions required before onset of failure
• Assessments include timed/time limit/rhythm assessments, with regard to age and sex.
• Examples include single leg raise 1/s (timed) and wall sit (timed)

Strength Exercise: Designing an Exercise Programme

• Understanding the patient's situation/perceived problem is fundamental
• Considerations include patient objectives, assessment of relevant contributing factors (physical conditions), and individualized program design.
• Re-evaluation is important, and assessments must be adapted to match the individual

Programme: Patient Assessment and Objectives

• Short-term and long-term objectives
• Previous experiences with strength training
• Motivators
• Beliefs about strength training- the importance of understanding patient experiences and beliefs towards strength training
• Barriers and Co-morbidities; which will influence the design of the strength exercise program

Programme: FITT-VP Prescription

• Frequency: How often?
• Intensity: How hard?
• Time: How long?
• Type: What exercises are done, and which muscle groups are targeted
• Volume: Total number of sets and repetitions
• Progression: When and how is the program progressed to create progressive exercise programming?

Programme: Frequency

• 2-3 weekly sessions, with regard to allowing a 48-hour break between sessions for recovery
• Sessions focused on global or separate muscle group work
• Frequency impacts adaptation

Programme: Intensity

• 1RM to ensure strength gains.
• Start with values close to 50% of 1RM; ideal values between 50% and 85% RM
• Respect rest time between sets.
• RPE (Rate of Perceived Exertion) is useful for individual monitoring of intensity; and can be used alongside RIR (repetitions in reserve)

Programme: Time

• Individualised exercise time and duration—with consideration to objectives, time availability and motivation
• The speed of execution will depend on objectives (e.g. endurance vs maximal strength)
• Use of metronomes or rhythms to facilitate control

Programme: Type

• Patient objectives determine training type: for example; in strength vs endurance
• Adapt the training program to maintain an appropriate form

Programme: Volume

• Volume refers to the number of workouts or sets performed
• Number of sets should be individualized
• Max Strength: higher intensity, low reps
• Muscular endurance: lower intensity, high reps

Programme: Progression

• Overload leads to adaptation.
• Increasing load (frequency, intensity and time) gradually leads to improved outcomes and adaptation.
• Periodization should be incorporated with appropriate rest and recovery periods.

Strength Exercise: Prescribing in presence of MSK-related pain

• Tailoring prescription to the patient's capabilities and pain thresholds
• Consider recovery time to prevent injury.
• Important to address psychological and social factors to reduce patient fear and support a successful program
• Type and intensity of exercise must be carefully considered, adjusted and monitored to improve outcomes through patient education and management of the conditions

Strength Exercises in presence of MSK-related pain: Recommendations

• Individualised programs for each patient
• A combination of aerobic, strength, and flexibility exercises
• Gradual progression to build confidence
• Continuous monitoring and adjusting prescription

Strength Exercises for Pain

• VAS (visual analogue scale) and RPE (Rate of Perceived Exertion) scales are important in assessing pain and the effectiveness of exercises.
• Values should be appropriate to individual pain tolerance

Strength Exercise: Blood Flow Restriction Training

• Low loads are used to exercise—with occlusion pressure as a percentage of arterial occlusion pressure (AOP)
• A hypoxic environment is created in the exercising limb
• Lower pressures may be more comfortable and effective

Blood Flow Restriction Training: Objectives, Indications, and Precautions

• Objective: Muscle hypertrophy, increased muscle strength, improved function/performance.
• Indications: Effective for conditions like ACL reconstruction, knee osteoarthritis, and sarcopenia
• Precautions: Crucial for individualized occlusion pressure, with low pressures often more effective.

Blood Flow Restriction Training: Effectiveness

• Improves muscle size, vascular function, and physical function.
• Does not exacerbate pain in conditions like knee osteoarthritis
• Less effective than heavy load training, but a viable alternative when heavy loads are not feasible.

STRENGTH EXERCISE: Clinical Case 1

• Woman with a 3-month history of shoulder pain exacerbated by tennis
• Case history of pain and the appropriate strength and endurance assessments for the patient condition should be incorporated and monitored.

STRENGTH EXERCISE: Clinical Case 2

• Male with patellar tendinopathy, pain exacerbated by standing and skiing
• Case history of pain and the appropriate strength and endurance assessments for the patient condition should be incorporated and monitored.