Strength Training

Question 1

What is the relation between force and the cross sectional area of a muscle ?

Answer 1

The larger the cross sectional area of a muscle, the greater the force developed by the muscle.

Question 2

What are the two mechanisms allowing increase of muscle force ?

Answer 2

• hypertrophy
• hyperplasia

Question 3

What is the difference between hypertrophy and hyperplasia ?

Answer 3

Hypertrophy is the increase of the VOLUME of muscles fibers, whereas hyperplasia is the increase in NUMBER of muscle fibers

Question 4

Describe the physiology of hyperplasia

Answer 4

Fusion of muscle fibers with embryonnary cells or of embryonnary cells together
In untrained subjects : 1% of new fibers
In power lift : 3% of new fibers
In power lift + steroids : 8% of new fibers
Therefore hyperplasia is negligeable compared to hypertrophy

Question 5

Describe the physiology of hypertrophy

Answer 5

• mechanical stretch increase workload
• involvement of growth factor
• within the muscles : Kinases proteins will increase the transcription of proteins by ribosomes
• induction of embryonic / fetal genes
• increased synthesis of contractile proteins (myosin and actin)
• increase of cross bridges
• increase of growth factor production

Question 6

What are the metabolic factors involved in muscle hypertrophy response ?

Answer 6

Lactate
Pi
H+
Ca 2+
Hypoxia
Electrolytes

Question 7

What are the hypertrophy mechanisms mediated by exercised induced metabolic stress ?

Answer 7

• fibers’ recruitment
• myokin production
• hormonal release
• production of «ROS»
• cellular swelling

Question 8

When does protein synthesis start after strength training?

Answer 8

It starts early after strength training but hypertrophy can only be seen after 4 to 6 weeks of training.
Repetition of training is necessary for hypertrophy to happen.

Question 9

Describe the adaptation pattern in muscle fibers

Answer 9

Increase of fast and slow fibers size during 16 weeks of training in a similar manner
Decrease of fast and slow fibers size after training with a greater decrease in fast fibers

Question 10

Which type of training is the most efficient to reach hyperplasia ?

Answer 10

Eccentric training

Question 11

Describe the muscle adaptation in eccentric training

Answer 11

First decrease in force and then increase at greater level (50N)

Question 12

Describe the muscle adaptation in concentric training

Answer 12

Increase in force but quick plateau (30N)

Question 13

Describe the changes in pennation angle due to muscle hypertrophy

Answer 13

The pennation angle increases with muscle hypertrophy.
Fibers are more oblique in order to increase their volume.
But if pennation angle > 45° the force vector reduces. This means that the muscle gets bigger but doesn’t develop more strength

Question 14

Explain the relation between strength training and motor units

Answer 14

• greater number of MU is recruited
• MU have a greater discharge rate
• happens after 50 days of strength training
• the increase in muscle force is explained by the increase in discharge rate of the MU

Question 15

What is cross adaptation ?

Answer 15

Studies have showed that training one muscle group induces an increase of force in the contralateral leg.

Question 16

What factors contribute to the increase of muscle force ?

Answer 16

Both neural and muscular adaptations

Question 17

What is the H-reflex ?

Answer 17

Also called Hoffman’s reflex, it is the earliest response of a muscle to stimulation of large afferent fibers in the muscle nerve.

Question 18

What is the impact of strength training on the H-refelx ?

Answer 18

H- reflex increases after training.
- at supraspinal and spinal levels
- enhancing drive from descending pathways
- decrease in presynaptic inhibition
- recurrent inhibition
- reciprocal inhibition