The human body is a living, breathing science experiment. Our bodies are designed to adapt to our environment and survive. Although we no longer need to hunt wild animals in the forest to feed our families or build pyramids with our bare hands, the human body is an amazing organism designed to effectively adapt to an ever changing environment. For these reasons, weight training programs remain effective in changing the physical makeup of the body.
As human beings, we want to look and feel our best. When it comes to physical activity and exercise, resistance training has been recognized for how it can effectively change the human body. Not everyone who participates in a cardiovascular workout program is looking to lose weight or change the way their body looks. Some may want to improve cardiovascular function (i.e. someone who is at risk for heart attack or stroke), prepare for a half marathon or simply increase energy and vitality. On the other hand, the majority of people who participate in a weight training program are looking to:
- Increase muscle size
- Increase muscle density (and tone)
- Increase the body’s metabolism (and lose weight)
A very small portion of people who weight train at the local gym are training to increase functional strength (i.e. manual laborer, competitive athlete, etc.). In today’s article you will learn about the science of resistance exercise and how weight training can change the physical makeup of the body (primarily muscle growth and development).
Muscle Growth & Development
When muscles undergo intense exercise, damage occurs to the muscle fibers. This is referred to as “muscle injury”. When this happens the body responds by starting the process to repair and replace damaged muscle fibers. Much like our skin will produce a scar after a severe cut, damaged muscle fibers have the ability to increase in size and strength after being exposed to intense exercise.
Satellite cells, the active cells involved in skeletal muscle repair, play a key role in the development of new components found within the muscle cells. As satellite cells multiply through this process:
- Some remain outside the muscle cell
- Some repair damaged muscle fibers within the muscle cell
- Some form new muscle protein strands within the muscle cell
In the end, satellite cells are the catalyst to promote growth of the muscle cells after a bout of intense exercise. Muscle growth (aka. muscle hypertrophy) can occur in one of two ways:
- Sarcomere hypertrophy
- Sarcoplasmic hypertrophy
Sarcomere hypertrophy (aka. functional hypertrophy) involves the growth of contractile proteins within the muscle cells (aka. myofibrils). Contractile proteins (actin and myosin) are the structural components found within myofibrils that physically contract and shorten muscle fibers. Satellite cells play a role in building more contractile proteins in the muscle cells.
Sarcoplasmic hypertrophy (aka. non-functional hypertrophy) involves increases in non-contractile cell components of a muscle fiber including:
- Sarcoplasmic reticulum – matrix that surrounds each myofibril and provides calcium needed for muscle contraction to occur.
- Sarcoplasmic – the fluid that fills the space in between myofibrils.
- Energy stores – primarily glycogen and creatine phosphate.
Muscle Repair & Recovery
After an intense workout, muscles experience cellular damage. Damaged tissues need to fully repair to prevent chronic damage or injury that can occur with subsequent workouts. It is important to give the muscle time to heal because fully repaired muscles are able to perform optimally when they are challenged again.
The recovery time for muscles varies because it is dependent on:
- Weight training experience
- Intensity of the workout
- Genetic factors
Muscles begin the repair process immediately after damage occurs following an intense workout. Within 24 hours the muscles reach the peak of the repair and renewal process. Approximately 36 hours after the workout the process is essentially complete. More experienced weight trainers may recover in as few as 30 hours whereas novice weight trainers may take up to 48 hours to recover fully.
In order to get the best results from your weight training workouts and the physical adaptations you are looking to achieve it is important to schedule your workout programs to include adequate rest and recovery.
Next Steps …
In “Workout Programs for Dummies – Muscle Development (Part III)” you will learn about key weight training principles to better understand program design for both exercise and recovery.