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Adaptations to Resistance Training (AKA Lifting, Weight Training)

Written by: Cassidy Ryan, MA

Whether you are a seasoned athlete or new to lifting, there is a lot of information out there regarding adaptations that occur from weight training. We are going to try to answer the following questions:

  • What changes to my body when I lift?

  • How long does it take to see changes?

  • Why am I sore?


What Changes to My Body? Strength Training Adaptations:

Often times we think of muscles getting bigger. This is coined with the term Hypertrophy.

The PUMP feeling is Transient Hypertrophy. This is increased muscle size from fluid accumulation in the muscle. It only lasts for a short period of time.

Chronic Hypertrophy is what we think of when muscle size increases from long-term training. There are two theories leading to this, with the first being thought of as the primary contributor.

  1. Fiber Hypertrophy: increases in the existing individual muscle fibers.

  2. Fiber Hyperplasia: increasing the number of muscle fibers via splitting.

How Long Does It Take? Neural Adaptations & Strength Gains:

According to literature, "it appears neural factors make their greatest contribution during the first 8 to 10 weeks of training. Hypertrophy contributes little during the initial weeks of training but progressively increases its contribution, become the major contributor after 10 weeks of training" (Wilmore et al., 2008, p.210).

See the timeline below for strength gains with NEW athletes.

The reason for massive gains in new athletes early on is because their body learns to move more effectively to produce more force. Within 3-6 months, one can see improvement from 25% to 100%, sometimes even more, from their initial strength.

*NOTE: Strength can be maintained for at least up to 12 weeks with reduced training frequency. BUT muscle atrophy (decreasing in size) begins quickly. So, rather than stopping training alltogether during busy times of life try and cut back on training days first.

What Is and What Causes Muscle Soreness:

Needing to 'get the lactic acid' out of your legs is not what causes muscle soreness.

  • Lactic acid levels return to normal within an hour post-exercise. This is why people prioritize cooldowns. When you move, you get your blood flowing to flush out exercise byproducts.

Delayed-Onset Muscle Soreness or DOMS is the pain we feel a day or two after.

  • 'The damage and repair process involves calcium ions, lysosomes, connective tissue, free radicals, energy sources, inflammatory reactions and intracellular and myofibrillar proteins. But the precise cause of skeletal muscle damage and the mechanisms of repair are not well understood" (Wilmore et al., 2008, p. 215).

  • AKA there are a lot of things that can cause muscle soreness!

  • Overall it is important to prioritize the following:

  • Gradual introduction to exercise if you are new. This prevents overtraining.

  • Focus on quality sleep.

  • Allow your body to recover. Rest days are important.

  • Fuel your body properly.


Wilmore, J. H., Costill, D. L., Kenney, W. L. (2008). Adaptations to resistance training. Physiology of sport and exercise (pp. 202-219). Human Kinetics.

Joyner, M. J. (2016, July 21). Debunking the myths about lactic acid, fatigue and recovery. Sport Illustrated.


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