Effect of Exercise and Training on the Muscular System

Why Exercise Changes Your Muscles

Exercise produces numerous physical, emotional, psychological and functional enhancements that extend beyond improved aesthetics (appearance) or performance.

As a trainer with years of hands-on experience in the gym, I’ve seen these changes play out repeatedly. From microscopic changes inside muscle cells to visible increases in strength, endurance, and coordination, training drives adaptation throughout the body.

In this article I will discuss how exercise affects the muscular system, and provide guidance for people to train creatively and maximize their long-term fitness success.

How the Muscular System Responds to Exercise

Understanding the Structure of Muscles:

Muscles are composed of many bundles of long, thin fibers. These long thin fibers contain inside of them many myofibrils, which are composed of the proteins that allow the muscle to contract (actin, myosin). When you contract your muscle (e.g., lift something up), the sliding of these two proteins against one another generates force.

Exercise challenges this system. Cause the muscles to respond by repairing damage to them, getting stronger, and working more efficiently to meet future demands.

Cellular Adaptations: The Foundation of Muscle Growth

The Role of Satellite Cells

One of the most significant adaptations occurs at the cellular level. Satellite cells, specialized stem cells found in the vicinity of muscle fibers, are crucial for muscle growth and repair. When muscle fibers experience low levels of controlled damage through resistance training, they will activate the satellite cells located nearby. The satellite cells will provide additional nuclei to the muscle fibers, promoting protein synthesis and aiding in the long-term growth of the muscle fiber. This process is necessary for both muscle recovery and hypertrophy.

Without proper training stimulus, these cells remain mostly inactive. With consistent training, they become key drivers of muscle remodelling and regeneration.

Hormonal and Molecular Responses to Training

Hormones & Exercise

If you want to build muscle, recover, and use energy efficiently during exercise, you need to understand how your body interacts with hormones when you work out.

There are several hormones involved in this process, including:    

• Growth Hormone (GH): Supports tissue repair and fat metabolism
• Testosterone: Enhances protein synthesis and strength development
• IGF-1: Stimulates muscle cell growth and repair
• Cortisol: Regulates energy availability but can impair recovery if chronically elevated

Short, intense resistance sessions tend to increase anabolism hormones, while long endurance sessions shift metabolic and stress-related hormones. Balance and recovery determine whether these responses support or hinder muscle adaptation.

Resistance Training and the Muscular System

Muscle Hypertrophy and Strength Development

The most effective means to achieve Maximum Physical Size through Resistance Training has been found to have three major factors affect Hypertrophy:

• Mechanical tension
• Training volume
•  Progressive overload

Progressive overload is the cornerstone of strength training. This means gradually increasing weight, repetitions, or total workload over time. When muscles are repeatedly challenged beyond their current capacity, they adapt by growing stronger and, often, larger.

Through modifying various variables including the length of time between repetitions, the tempo of lifting and the proximity to muscular failure will further maximize the results received from Resistance Training.

Endurance Training and Muscle Adaptations

Mitochondria and Fatigue Resistance

Endurance training affects muscles differently than resistance work. Instead of increasing fiber size, it enhances mitochondrial density, capillary networks, and oxidative enzymes.

These adaptations improve:

• Oxygen delivery
• Energy efficiency
•  Fatigue resistance

As a result, muscles can perform for longer periods without exhaustion. Endurance training is especially beneficial for cardiovascular health and metabolic function.

Mixing Endurance and Strength Training

Properly combining resistance and endurance training is vital. These two styles of training activate 2 different pathways. Too much volume of endurance training will impede strength development. When done correctly though they work together to enhance overall athletic performance and health for a long period of time.

Practical Training Guidelines for Muscle Adaptation

Warm-Up and Preparation

• Perform 5–10 minutes of dynamic movement
  
• Focus on mobility and muscle activation
  
• Prepare joints and connective tissue for loading
  

Resistance Training Recommendations

• Sets: 3–6 per exercise
  
• Reps: 4–12 depending on strength or hypertrophy goals
  
• Frequency: 2–4 sessions per muscle group per week
  
• Progression: Increase load by 2–10% or add 1–2 reps when possible
  

Endurance Training Recommendations

• Duration: 20–60 minutes per session
  
• Intensity: Steady-state or interval-based
  

Frequency: 2–5 sessions per week depending on goals

Recovery: Where Muscle Growth Actually Happens

Importance of Sleep and Rest

Training creates the stimulus, but recovery produces results. During rest, the body repairs muscle tissue, restores energy stores, and regulates hormones.

Inadequate recovery leads to stalled progress and increased injury risk. Sleep, rest days, and load management are essential components of any effective program.

Nutrition and Muscle Health

Protein and Energy Intake

Protein provides the building blocks for muscle repair and growth. Most individuals aiming to build muscle benefit from 1.6–2.2 grams of protein per kilogram of body weight per day. Individual needs vary, so consulting a qualified nutrition professional is recommended.

Adequate carbohydrates support training intensity, while healthy fats contribute to hormonal balance and overall health.

Exercise, Aging, and the Muscular System

Muscle mass naturally declines with age, a condition known as sarcopenia. However, regular resistance training significantly slows this process.

Older adults respond well to strength training but often require:

• Longer recovery periods
  
• Gradual progression
  
• Greater emphasis on mobility and joint health
  

Consistent exercise improves strength, balance, independence, and quality of life across all age groups.

Injury Prevention and Coaching Cues

To protect the muscular system:

• Start with manageable loads
  
• Use full, controlled ranges of motion
  
• Stop training if pain is sharp or persistent
  
• Track progress and recovery markers
  
• Periodize training to avoid plateaus
  

Good form and patience prevent most training-related injuries.

Final Thoughts: Train With Purpose

Exercise reshapes the muscular system at every level—from muscle fibers and hormones to strength, stamina, and long-term health. The science aligns with what experienced trainers observe daily: smart, consistent training works.

Small, intentional steps taken over time outperform extreme, inconsistent efforts. Train with focus, recover well, and let adaptation do its job. When applied correctly, exercise is one of the most powerful tools available for improving muscle function, physical performance, and overall well-being.