Why am I Sore After Exercise?

Published July 18, 2022

By: John Kirscht Jr., PTA

If you are a regular at the gym, or just started an exercise routine, it is common to experience muscle soreness following participation in strenuous activity. Soreness or discomfort after a strenuous or new strength event is very common.  Understanding muscle soreness as a natural outcome following physical activity, how to mitigate it, and what is normal all help drive a safer and more successful exercise program.

Normal post exercise pain not related to injury is muscle soreness, that can be attributed to the strain and mild damage to the sarcomere (contractile element of muscle tissue). This degeneration and breakdown of the sarcomere initiates the body’s inflammation response and is supported by the surrounding connective tissue. The inflammatory cells stimulate pain receptors which are associated with two stages of discomfort: Acute Muscle Soreness (AMS), or Delayed Onset Muscle Soreness (DOMS).

muscle soreness after working out

Acute Muscle Soreness

Acute Muscle Soreness, or AMS is pain felt in muscles immediately afterwards or up to 24 hours following exercise. The pain can occur within a minute of a muscle contracting, and usually dissipates within two to three minutes, or up to several hours after relaxing the targeted muscle group. There are two common causes of AMS, one being the build up the accumulation chemical end products of exercise lactic acid, and the other being muscle fatigue, where the muscle struggles to contract. When you work out, the body uses oxygen to break down glucose (sugar) for energy. During intense exercise, enough oxygen may not be readily available to complete the process, so a by product called lactate is made. The body can break down lactate without using oxygen, but this lactate, or lactic acid can build up in our blood stream faster than we burn it off.  Lactic acid and other waste product build up creating a shift in the PH in the muscle tissue.  The accumulation is associated with symptoms such as a burning sensation in the affected muscle group, cramps, and weakness.  These symptoms are very commonly benign and are safe when treated correctly.

Delayed Onset Muscle Soreness

The repair of the sarcomeres and surrounding connective tissue leads to delayed onset muscle soreness (DOMS) which occurs anywhere between 24 to 72 hours following physical activity. DOMS is believed to be caused by eccentric, or lengthening exercise of the muscle while it is under tension.  The stress of this mechanic causes small scale microtrauma to the muscle fibers. This microtrauma is a positive response and necessary event to hypertrophy and adaptation.  As a basic rule, the body adapts to both stresses applied and not applied to the body. This microtrauma and associated biomarkers are simple level indicators to the body that it was not effective in meeting the force demands of the tasks the individual requested from it.  The body recognizes its own short comings and then during the reparative stage it encourages hypertrophy of the tissue, and other bio-adaptations to improve its capabilities in future events.  There are of course thresholds to how extreme we should push the body, and how much damage it can safely handle, recover from, and adapt from.  DOMS at low levels is safe, at higher levels the muscle breakdown can result in negative health events such as rhabdomyolysis, tendonitis, moderate level muscle strains, and more! Delayed onset muscle soreness can be mitigated or prevented by gradually growing into an exercise program.

How to reduce soreness?

To help relieve muscle soreness, try take a global approach to your gym routine. Alternate target muscle groups during different days of the week and allow target muscle groups to rest while working out different parts of the body (leg day vs. chest day, for example). Additionally, gentle stretching, rest, as well as modalities such as ice and hot packs can help alleviate muscle soreness. The aches and pains should be minor and are indications that your body is adapting to the exercise regimen.  

While it is not possible to completely prevent muscle soreness after exercise, the best way to reduce the severity of symptoms is to build up slowly to any exercise routines. This cautious approach will allow the muscles time to adapt to the changes they are experiencing. If you are experiencing pain or soreness after a workout or injury, trust the experts at CAO. We offer 60 convenient locations across Maryland, DC, and Virginia with over 400 providers to help get you back on the road to recovery. Schedule an appointment with CAO.