Soft Tissue Injuries & Muscle Pains that Prevent Athletic Play

Soft Tissue Injuries that Red Light Therapy Helps Heal

As I set out to explain how red light therapy helps athletes heal, I realized that I had forgotten the difference between a strain and a sprain. I researched and explained types of athletic injuries, and causes of delayed onset muscle soreness, below.

Soft tissue injuries involve ligaments, tendons, muscles and bursa:

  • Ligaments attach bones to one another
  • Ligaments get sprained
  • Tendons attach muscles to bones
  • Tendons get inflamed and strained
  • Muscles power the body to move
  • Muscles get strained and bruised (they get “contusions”)
  • Bursa cushion joints
  • Bursa get inflamed

Delayed onset muscle soreness has at least six causes, including:

  • lactic acid buildup
  • connective tissue damage
  • inflammation
  • muscle damage
  • muscle spasm
  • enzyme efflux (flowing out)

To see how red light therapy helps with soft tissue injury and DOMs, see my articles:

The Soft Tissue Injuries that Bench Athletes

Sudden trauma and repeated misuse cause athletic soft tissue injuries.

Soccer player lying on green field, holding his head in his hands
Soccer players with soft tissue injuries healed faster with red light therapy

Sudden trauma includes body blows, twists and falls. These cause sprains, strains and bruises.

Repeated trauma is a re-injury through use before healing. This causes tendinitis and bursitis.

Sprained Ligaments

Ligaments are soft tissue connecting the ends of bones to one another.

Sprains are acute trauma injuries in ligaments.

A sprain is tearing of a ligament.

Sprains typically occur in ankles, wrists and knees.

Soccer player kicking ball with referee behind him
Ligament damage heals faster with red light therapy

Sprained ligament symptoms include pain, swelling, bruising, and inflammation.

Strained Muscles and Tendons

Tendons attach muscles to bones.

Strains are acute trauma injuries in muscles and in tendons.

Strains are common in hamstrings, hands, and elbows.

Man in bike shorts holding a red inflamed knee
Red light therapy helps athletes play longer before exhaustion causes injuries.

A strain is a muscle or tendon injury from a blow, twist, fall, or misuse.

Overstretching and tearing are common causes of strains.

Strain symptoms include weakness, inflammation, muscle spasms, swelling, pain, and cramping.


Contusions are acute trauma muscle fiber injuries.

A contusion is also called a bruise.

Muscles bruise when hit with hard blows or are jammed against hard surfaces.


Tendinitis is an overuse injury to the tendon or the tendon’s covering (the sheath).

Small stresses cause injuries that do not heal before the small stresses aggravate the tendon again.

The result is swelling and pain.

Tendinitis is common in the elbow, shoulder, knees, forearms, and ankles.


Bursitis is an overuse injury of the bursa sacs that cushion elbows, knees, hips, and heels.

The small stresses that cause tendinitis can cause bursitis as well.

Bursitis symptoms include swelling and pain.

Sprains, Strains and Other Soft-Tissue InjuriesOpens in a new tab.

Soft-Tissue InjuriesOpens in a new tab.

Sprains, Strains & Soft-Tissue InjuriesOpens in a new tab.

Delayed Onset Muscle Soreness (DOMS) that Interferes with Play

Physical therapist pulling on leg of patient sitting across from him
Red light therapy shortens delayed onset muscle damage soreness

Delayed onset muscle soreness is muscle pain occurring 24 to 72 hours after exercise.

Onset is correlated with new and/or intense exercise activity.

DOMS is caused by any mixture ore these conditions[1]:

  • lactic acid buildup
  • connective tissue damage
  • inflammation
  • muscle damage
  • muscle spasm
  • enzyme efflux (flowing out)

[1] Cheung K, Hume P, Maxwell L. Delayed onset muscle soreness : treatment strategies and performance factors. Sports Med. 2003;33(2):145-64. doi: 10.2165/00007256-200333020-00005Opens in a new tab.

Lactic Acid Buildup that Causes DOMS

Lactic acid production is the result of energy demand with insufficient oxygen to make adenosine triphosphate (ATP).

Women tennis player holding sore elbow
Red light therapy helps wtih tennis elbow soft tissue injuries

The muscles demand energy to move, but the lack of oxygen prevents its production.

Pyruvate converts to lactic acid in anaerobic conditions.

Connective Tissue Damage That Causes DOMS

DOMS can be caused by connective tissue damage.

Connective tissue consists of collagen fibers, reticular fibers, and elastin fibers[2].

Exercise damages the fibers, causing delayed onset muscle pain.

Collagen fibers are supportive and resist pulling tension.

Reticular fibers support tissues with a different matrix but in a manner similar to collagen fibers.

Elastin fibers rebound after stretching.

Damage to the connective tissue breaks down the body’s ability to support muscles and organs.

[2] Kamrani P, Marston G, Jan A. Anatomy, Connective Tissue. [Updated 2022 Jan 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

Inflammation that Causes DOMS

Men running on indoor track
Athletes pre-conditioning with red light therapy have fewer injuries

Inflammation is a natural immune response that gathers white blood cells at an injury. Acute inflammation is healthy, but chronic inflammation is not.

Chronic inflammation damages soft tissue, resulting in pain and decreased functionality.

Chronic inflammation is associated with diabetes, obesity, depression, and cardiovascular disease[3].

[3] Pahwa R, Goyal A, Jialal I. Chronic Inflammation. [Updated 2022 Jun 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

Muscle Damage that Causes Doms

Exercise-induced muscle damage causes loss of function, reduced strength, and reduced range of motion.

Muscle damage occurs when the muscle is pushed beyond its aerobic capacity[4].

Muscle damage triggers an influx of proteins that might be the source of muscle damage (and delayed onset muscle soreness) pain.

[4] Exercise Induced Muscle DamageOpens in a new tab.

Muscle Spasms That Cause DOMS

High intensity exercise and muscle overuse are two of the many causes of muscle spasms[5].

A muscle spasm is a constricted tightening of the muscle into a cramp, and can be very painful.

[5] Muscle SpasmsOpens in a new tab.

Enzyme Efflux that Causes DOMS

Man on soccer field holding shin while pressing forehead into field turf
Red light therapy reduces the pain of soft tissue injury.

The Enzyme Efflux theory of DOMS is that micro traumas in the muscle cause a calcium buildup that inhibits cellular energy production.

This leads to protein breakdown and an accumulation of prostaglandins, histamines, and potassium.

The lack of energy and buildup of unwanted material causes the muscle soreness.

Caroline Bogart

I research the bloody hell out of everything that interests me, then translate it into blog posts to solidify my knowledge and share the information.

More athletic injury therapy info