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Muscle Soreness Pt. 1: Why Do My Muscles Get Sore?

Updated: Oct 16, 2022

by Melanie Brohm, B.Sc., RMT

It doesn’t matter if it is day 1 or day 1000+ with Yvonne’s Fitness....

It doesn’t matter if it is Zumba, Strong Nation, Yoga, Zumba Toning, Zumba Gold, Zumba Kids or doing a combination of everything while soaking up the sun on the Zumba Yoga Mexico Trip....

We all get this at one point or another.... muscle soreness.

Muscle soreness is a side effect of the stress put on the muscles with any form of exercise. To generalize, there are two types of muscles soreness – delayed onset muscle soreness (DOMS) and acute strain. Before we distinguish between the two types of muscle soreness, let’s examine what happens to the muscle itself by asking a few questions.

What is the difference between toned, tight, and taut muscles? (

Muscles and group of muscles work in pairs and are controlled by the nervous system to allow for movement around a specific joint. Picture a pulley system – as one side increases in length (stretch or relax) the opposite side will decrease in length (shorten or contract – the back arrow in the diagram).

When a muscle is toned, the length-tension relationship is balanced. The muscles work efficiently with respect to strength, flexibility and respond well to the nervous system. The muscles return to their normal resting length.

When a muscle is tight, the length-tension relationship is not balanced. There is more “tension” in the muscle. The two ends of the muscle are closer together – even at rest. This occurs in muscles that are in a shortened position for a long period of time. You see this in people with rounded shoulders and forward head posture – the chest, front of the neck, shoulder and even arm muscles adapt over time to this shortened position – and can even change the shape of the bones of the joints. These short and tight muscles cannot stretch or return to normal anatomical length – even with the nervous system trying to scream relax!!

When a muscle is taut, the length-tension relationship is not balanced either! There is more “length” in the muscle. The two ends of the muscle are pulled further apart – even at rest. Picture stretching an elastic to its limit. That is what is happening to a taut muscle – BUT it is always trying to return to a normal length-tension. So, the resistance you feel against stretching the elastic further apart is the constant contraction happening in the muscle from the nervous system trying to scream shorten!! The same person with the rounded shoulders and forward head posture – the upper and mid-back, rotator cuff and back of the neck muscles are lengthened, overstretched and tired.

MYTH – You can lengthen a muscle. You cannot permanently change the anatomical length of the muscle. With stretching, you reduce the body’s protective response or stretch reflex. The stretch reflex is the body’s protective reflex from potential injury from an overstretch – called an acute strain with muscle fibers or an acute sprain with ligaments. When you feel an increase in flexibility or range of motion – it is the return to the normal anatomical length limits of the muscle – remember the length-tension relationship?

What are the steps of a muscle contracting? (

To keep it simple, there are three steps to a muscle contraction. The nervous system sends a message to the muscles that starts a chemical reaction. The chemical reaction leads to the muscle fibres to collectively shorten – this is the muscle contraction. When the nervous system stops sending the message, the chemical reaction changes, and those muscle fibres collectively return to their original position – this is the muscle relaxing or returning to its previous length.

What is muscle soreness?

Muscle soreness comes from the stress placed on the muscles. This can come from minor inflammation that occurs with repetitive muscle contractions. It also comes from micro tearing of the individual muscle fibres when a load is added – using body weight, toning sticks, resistance bands or water, etc. Muscle soreness is typically a sign that you are getting stronger. As those muscle fibres heal, they become larger and stronger than before. This is how the body can build strength, endurance and flexibility. Muscle soreness usually occurs when there is a new challenge to the body – starting a new program, adding a new exercise, decreasing rest time between sets or increasing the intensity through speed, repetitions or weight lifted. Muscle soreness can occur in any muscle but is usually felt in the larger muscle groups – and depends on the type of workout. This is why your programs is always changing through Yvonne’s Fitness!

Acute Injury vs Delayed Onset Muscle Soreness (DOMS)?

Muscle soreness usually starts the next day. Why? It is still being researched. The theory is that the normal inflammation process that occurs hides this soreness. This is also a key distinguishing factor between muscle soreness and injury.

With an acute injury – a muscle strain grade 2 or 3 – there is a sudden onset, sharp pain when the injury occurs, possible muscle spasms, swelling, muscle weakness and limited motion. This can occur when using poor body mechanics, tripping, falling or not listening to the body’s warning signs. Depending on the severity, one should seek medical guidance for treatment. There is controversy over the initial treatment of RICE (rest, ice, compression and elevation) vs METH (movement, elevation, taping/traction, heat) ( Healing time can take 6-8 weeks.

Delayed Onset Muscle Soreness (DOMS) – considered in some textbooks a grade 1 muscle strain - is an annoying soreness that can start between 12-24 hours after activity. It lasts between 24-72 hours with the peak of discomfort 48 hours after activity. There is little to no pain at rest. Normal strength and normal range of motion with some mild discomfort. You can still exercise with DOMS but modify accordingly. In weight training programs there is a changing focus on the muscles worked – leg vs back vs arms. We see this in all of Yvonne’s Fitness programs with modification options, slow progressions and changing quadrants. DOMS is a complicated topic and is still being researched.

What about Lactic Acid?

MYTH – Lactic acid was thought to be the cause of muscle soreness, fatigue and reduced performance due to the build up in the muscle tissues when oxygen was low – like during exercise.

You hear about lactic acid in the lactic acid cycle – also known as the Cori cycle or glucose-lactate cycle. It is a metabolic pathway where lactate, produced by anaerobic (no/low oxygen) glycolysis (breakdown of sugars) in muscles, travels to the liver and converted to glucose, then returns to the muscle to be used again. (

This Cori cycle is important in that it helps our bodies produce the additional energy needed by muscles when we exercise.

This blog is the first in a 3-part series about Muscle Soreness. Stay tuned for parts 2 & 3!

*Melanie Brohm B.Sc., RMT of Brohm Therapeutic Massage is a highly-educated Registered Massage Therapist, and also a long-time Zumba/Yoga participant at Yvonne's Fitness. If you would like to learn more about what she does, or find out about her services, you can find her online here.

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1 Comment

Cathy Enns
Cathy Enns
Oct 13, 2022

Great Article😉

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