Adaptations to resistance training Flashcards
What changes do we observe in performance as a result of resistance training?
People who perform resistance exercises:
• Can lift more weight
(increased strength)
• Can lift more weight for a greater duration or number of times (repetitions)
(increased endurance)
• Can lift more weight in a shorter period of time
(increased power)
Changes in performance are dependent on the design of the exercise (what parameters and what variables)
What changes do we observe in body composition* as a result of resistance training?
People who perform resistance exercises:
– Have increased muscle tone
– Have increased muscle size
*this refers to changes in skeletal muscle only. There are other mechanisms responsible for changes in body composition; reduced % body fat and increased bone mass for example
Changes in body composition are dependent on the design of the exercise (what parameters and what variables)
Those changes in performance and body composition are the result of 3 broad categories of ADAPTATIONS:
1) Adaptations in the Nervous System (Neural)
2) Adaptations in the Skeletal Muscle System
3) Adaptations in the Osseoligamentous System
NERVOUS SYSTEM CHANGES
What is neural adaptation?
Improved performance due to:
– Increased motor unit recruitment
– Decreased autogenic inhibition
• Inhibitorymechanismstoprevent generation of levels of force that could cause structural damage
– Coordination of agonist, synergist and antagonist muscle
another NS change is decrease fall risk
NERVOUS SYSTEM CHANGES
What evidence supports neural adaptation?
Changes in performance (strength) are seen before changes in skeletal (significant diff. seen at 6 weeks)
muscle composition
– Small insignificant increase in fibre hypertrophy but significant gains in strength after 2 weeks of resistance training
– Increase in EMG in first 4 weeks of training
– Increasing contribution of hypertrophy after 4-6 weeks of training
Strength gains in muscles that have not been trained
– Significant strength gains in opposite untrained arm
– Improvements with imagined training
SKELETAL MUSCLE CHANGES – STRENGTH TRAINING ADAPTATIONS
What is hypertrophy?
Increase in size of existing muscle fibres
– Net increase in muscle protein synthesis
– Greater number of actin and myosin filaments
What evidence supports hypertrophy?
Increased strength associated with increased fibre size after 12-week training program
• 25% increase in biceps 1 RM
• 13% increase in muscle fibre area with no increase in fibre number on MRI (i.e. no hyperplasia)
• Increased number of capillaries per fibre (increase in oxygen and fuel to muscles)
SKELETAL MUSCLE CHANGES – STRENGTH TRAINING ADAPTATIONS
What is hyperplasia?
Increase in absolute number of muscle fibres
• Arguments
– Fibre splits into daughter cells
• Someevidenceinanimal studies but human studies are limited
– Change in fibre types
• Evidenceofadaptationbetween Type IIA and IIB with strength training, but not conversion between Type I and Type II
What evidence supports hyperplasia?
Fibre type changes occur early in strength training after 2-4 weeks of training (6-12 reps to failure x 3 sets 2x/week)
• Increase in maximal dynamic strength
• Decrease in Type IIB fibres
• Non-significant trend of increased Type IIA fibres
• Reverse occurred with detraining
Other changes in skeletal muscle structure
- Decrease in or no change in capillary bed density
* Decrease in mitochondrial density (density not absolute no.) and volume
PHYSIOLOGICAL CHANGES – ENDURANCE TRAINING ADAPTATIONS
Key differences
• Increase in capillary bed density
• Increased size and number of mitochondria
– Improved ability to generate ATP by oxidative phosphorylation
• Minimal or no muscle fibre hypertrophy
• No change in lean body mass
OSSEOLIGAMENTOUS AND OTHER CHANGES
What other changes occur?
• Increased bone mineral density • Increased connective tissue, tendon and ligament strength • Altered body composition – Increase lean body mass – Decrease % body fat
OSSEOLIGAMENTOUS AND OTHER CHANGES
Bone mineral density
Men and women aged 60-83 years participated in control, high-intensity (HI) or low-intensity (LI) resistance exercise program
– LI-50%of1-RMx13reps
– HI- 80%of1-RMx8reps
– Both groups - 1 set of 12 exercises 3d/week x 24 weeks
– Both groups - ↑ 1 RM strength for each exercise
– Both groups - evidence of ↑ bone turnover (osteoblasts and osteoclasts)
– HI - ↑ bone mineral density of the femoral neck
OSSEOLIGAMENTOUS AND OTHER CHANGES
Connective tissue strength
Tissue strength increases to support the increase muscle size and strength
• Increased thickness of connective tissue surrounding muscle
• Increased tendon strength at musculotendinous junction
• Increased ligament strength at bone
type I fibers
Resistance to fatigue: high Capillary density: high Energy System: aerobic diameter: small twitch rate: slow maximum muscle-shortening velocity: slow
