The Physiology of Resistance/Strength Training Flashcards
Define Muscular strength
Maximal force that a muscle group can generate (1-RM)
Define Muscular endurance
Ability to make repeated contractions against a submaximal load
Strength training - how many reps till fatigue in high-resistance and low-resistance training?
*High-resistance training (that is 6 to 10 reps till fatigue).
- Results in strength increases.
* Low-resistance training (that is 35 to 40 reps till fatigue).
- Results in increases in endurance
What does ageing result in?
A loss of muscle mass and strength
- loss of muscle mass (sarcopenia)
- atrophy type 2 fibres
- reduced number of both type 1 and 2 muscle fibres
- Resistance training promotes hypertrophy/strength gains in older individuals but lower than young individuals.
What is responsible for early gains in strength, and what is this evidenced by?
Neural adaptations - as evidenced by:
- muscular strength increases in first 2 weeks of training without increase in muscle fibre size
- phenomenon of “cross-education” - training of one limb results in increases of strength in UT limb
What adaptations within the muscle fibre occur later on…?
- increased muscle fibre specific tension
- increased muscle mass
What adaptations are included in the early gains related to changes in nervous system?
- Increased Neural Drive (measured via EMG).
- Increased number motor units recruited.
- Increased firing rate of motor units.
- Increased motor unit synchronization.
- Improved neural transmission across neuromuscular junction.
What is the mechanism responsible for training-induced increase in specific tension in type 1 fibres?
Appears to be linked to increased calcium sensitivity - results in greater number of cross-bridges bound to actin
Define hyperplasia
Increased number of fibres
Define Hypertrophy
Increased CSA of muscle fibres
- likely dominant factor in resistance training-induced increases in muscle mass.
- due to actin and myosin
- evidence of resistance training-induced transition from type IIx to IIa (but not type II to type I)
Protein synthesis must exceed breakdown for ? weeks or more to achieve significant fibre growth
3 weeks or more
What are the key factors which contribute to resistance training-induced increases in MPS (signalling events)?
- mRNA increases resulting in PS at ribosome
- Ribosomes increase in number and elevate muscle’s PS capacity
- Activation of the protein kinase mTOR is the KEY FACTOR ACCELERATING PROTEIN PS following bout of resistance training
What 2 signalling molecules stimulate mTOR activation?
Phosphatidic acid (PA) & Ras homolog enriched in brain (Rheb)
Time course of molecular responses to resistance training - What are the post-exercise molecular responses ?
Secs - increased Rheb and PA
Mins - increased mTOR activation
Hours - increased PS
What other hormones are linked to mTOR activation
IGF-1 and GH
What effect does resistance training have on satellite cells?
- RT activates satellite cells to divide and fuse with adjacent muscle fibres to increase myonuclei.
- RT-induced increases in myonuclei results in a constant ratio between number of myonuclei and size of muscle fibre
- Addition of new myonuclei to fibres is likely required to support increased PS in larger muscle fibres
What effect does age have on RT induced satellite cell activation?
Resistance training-induced satellite cell
activation is blunted in older individuals
Approx ?% of the differences in muscle mass between individuals is due to genetic variation?
80%
Is the rate of strength loss faster or slower than in endurance training, following the cessation of exercise?
Slower
Recovery of dynamic strength loss can occur rapidly (within ? weeks) with retraining.
6 weeks
Muscle memory is the rapid recovery during retraining, after prolonged periods of inactivity. What is muscle memory due to?
resistance training-induced increases in myonuclei in the trained fibres that are not lost during detraining. Maintaining myonuclei provides advantage in rapid protein synthesis upon retraining
20-30 days of muscle inactivity can results in ?% reduction in muscle fibre size.
20-30% reduction.
- Conservation of muscle mass is dependent upon balance between protein synthesis and rates of protein degradation
What is the key mechanism responsible for inactivity-induced muscle atrophy?
Increased radical production promotes muscle atrophy during prolonged inactivity by depressing protein synthesis and increasing degradation.
Studies conclude that concurrent strength & endurance training impairs strength gains compared to strength training alone. What are the potential mechanisms for this?
Neural factors (impaired MU recruitment)
Overtraining
Depressed PS (endurance training cell signalling can interfere with PS) - via inhibition of mTOR by AMPK activation.
