Week 9 - The effects of Resistance training Flashcards
Muscular strength
maximal force that a muscle group can generate (1RM)
Muscular endurance
ability to make repeated contractions against a submaximal load
What does high-resistance training (6-10 reps till fatigue) result in?
strength increases
What does low-resistance training (35-40reps till fatigue) result in?
endurance increases
What does ageing result in?
- the loss of both muscle mass (termed sarcopenia) and strength
- atrophy type two fibers
- reduced number of both type I and II fibers (loss of motor neurons)
How does resistance training increase muscle strength?
by changes in both the nervous system and muscle fiber size/function
Neural adaptations are responsible for early gains in strength (first 8 weeks).
- This is supported by the fact that muscular strength increases in first two weeks of training without increases in muscle fiber size.
Adaptations within muscle fibers occur later. For example, increase in muscle fiber specific tension and increased muscle mass.
What are the neural adaptations that result in early gains in muscle strength?
- Increased neural drive
- Increase number of motor units recruited
- Increased firing rate of motor units
- Increased motor unit synchronization
- Improved neural transmission across neuromuscular junction
- Increased size of NmJ and vesicles containing ACh
Summarise the 4 resistance training-induced physiological adaptations.
1) NS: Increased neural drive + possible changes in ratio of agonist/antagonist activation which occurs rapidly after training (2-8 weeks).
2) Increased muscle fiber force production, specifically in type I fibers due to an increased calcium sensitivity which results in a greater number of cross-bridges bound to actin.
3) Hypertrophy (specifically in type II fibers) which increases muscle mass.
4) Muscle fiber type shift from type IIx to IIa fibres.
What is the dominant factor in resistance training-induced increases in muscle mass?
Hypertrophy - incr. cross-sectional area of muscle fibres
What is hypertrophy due to?
increased muscle proteins - actin and myosin
What transition occurs in fiber type due to resistance training?
type IIx to type IIa
What is the difference between hyperplasia and hypertrophy?
Hyperplasia is the increased number of fibers whereas hypertrophy is the increased cross-sectional area of muscle fibers.
Muscle growth occurs because protein synthesis exceeds rate of breakdown. But how long must synthesis exceed breakdown to achieve significant fibre growth?
3 or more weeks
What % increase in muscle protein synthesis do we see with 1-4 hours post-exercise?
50-150%
This increase in muscle protein synthesis is elevated up to 30 to 48h after training depending on training status.
What are the key factors that contribute to resistance training-induced increases in muscle protein synthesis?
- mRNA increases resulting in protein synthesis at the ribosome.
- Ribosomes increase in number and elevate muscle’s protein synthesis capacity.
- Activation of the protein kinase mTOR is THE KEY FACTOR accelerating protein synthesis following a bout of resistance training.