Tag Archives: trouble running laps

“How can anyone be so out of shape?” 

“Why don’t they  just try harder?” 

“Don’t they realize they’ll have to run more laps?”

Anyone who has ever ran laps in grade school gym class can probably recall stragglers.  Some were children with asthma or other health issues, but some consistently finished for no obvious reason.  For such children, it may very well have been the case that trying harder simply wasn’t an option.

When a child with no obvious physical infirmity is unable to meet basic physical fitness criteria, effort should be made to rule out McArdle’s disease, a rare and often undiagnosed muscle disorder marked by extreme exercise intolerance.

How McArdle’s Disease Makes it Difficult for Children to Run Laps

Also known as glycogen storage disease Type V or phosphorylase deficiency, McArdle’s disease is an inherited condition which impairs energy metabolism in skeletal muscle. During moderate to intense physical activity an enzyme called glycogen phosphorylase provides contracting muscles with the energy required to do work. In McArdle’s disease this enzyme either is either non-functioning or missing, and the result is premature exhaustion and failure which may be accompanied by cramp-like injuries to muscle tissue.

Screening Children for McArdle’s Disease: Simple Signs to Look For

Even with the wealth of information now available on the web, screening McArdle’s disease in children remains challenging. Undiagnosed individuals may have a healthy appearance and symptoms can easily be mistaken for laziness or behavioral problems.

For this reason, it is critical that the right people know exactly what to look for. Physical education instructors, teachers, school nurses and even other students can screen McArdle’s disease on the basis of one or more of the following criteria:

  • They seem abnormally out of shape despite a healthy appearance.  People with McArdle’s disease have trouble sustaining low- to moderate-impact activities such as climbing stairs or walking steep inclines, and consistently perform below average on standardized fitness evaluations.
  • They have trouble getting in shape.  Because their muscles do not metabolize energy normally people with McArdle’s fail to respond as expected to endurance exercise regimens.
  • They may experience cramping injuries accompanied by dark-colored urine.  As children reach adolescence, increased body weight, musculature and opportunity for competitive sports training may precipitate episodes of muscle failure and injury during activity. Telltale symptoms include painful cramp injuries called rhabdomyolysis, sometimes accompanied by myoglobinuria, a potentially life-threatening condition indicated by urine darkened by proteins entering the bloodstream from damaged muscle tissue.
  • They may avoid fitness evaluations or other physical activities. The conspicuous symptoms of McArdle’s disease can make children self-conscious and embarrassed, and the stigma of feeling different may lead them to avoid participating in physical activities altogether.


If you know of anyone who fits any of these criteria, please reach out to them and learn more about the challenges they face.  Children with undiagnosed McArdle’s disease may suffer from the perception that they are simply out of shape or lazy, so approach them with discretion but be patient and persist in asking the right questions.

Most importantly, always remember that diagnosis and treatment of McArdle’s disease should be left to qualified medical professionals.  Recent advances in medicine make conclusive diagnosis a matter of one or two clinic visits and a minor blood test.

Children and adolescents with McArdle’s disease can live active lives and be physically fit, provided challenges are undertaken safely and within the scope of the limitations of this disease.  Catching symptoms early gives children with this rare disease a better chance to feel normal.

For additional information about McArdle’s disease visit any of our homepage resources or the Muscular Dystrophy Assocation website.


Children with McArdle’s Disease are at significant disadvantage.  Children aren’t able to articulate themselves as well as adults and their symptoms are easily confused with being lazy or stubborn or simply uncooperative.  Children who are lagging behind because they are experiencing painful muscle failure from McArdle’s Disease may find their discomfort compounded by scolding or teasing from classmates or teachers. At some point, all children endure some form of teasing from friends or siblings or classmates.  However, those children more vulnerable to teasing for whatever reason – small stature, weight issues, appearance, or anything else – may be singled out, and excessive attention of this kind is unhealthy.

It is incumbent upon grade school physical education teachers, nurses, pediatricians and anyone else in a position of relevant authority to educate themselves on McArdle’s Disease and other conditions whose symptoms are easily mistaken for behavior issues or lack of cooperation.  Even the most observant teacher cannot tell simply by looking at a child whether or not their muscles work properly, and the way the symptoms of McArdle’s Disease manifest is deceptively similar to a simple lack of physical condition or laziness.

How to Know if a Child Has McArdle’s Disease

Here are some things you may observe:

  • Does the child complain of weariness on even moderately long walks?
  • Do smaller children complain of weariness and ask to be carried?
  • Do hills, stair cases, and other inclines elicit the responses above?
  • Does the child complain of “pain” in the legs in such incidents?
  • Does the child have difficulty performing even an average number of sit-ups or push-ups, even in a modified form?
  • Does the child have difficulty or otherwise avoid running laps in gym class?
  • Does the child demonstrate, in general, a lack of physical fitness that contradicts an otherwise healthy appearance, assuming they are not overweight?
  • Has the child ever complained of or demonstrated unusual muscle stiffness and cramping?
Any of these observations are worth investigating.  Again – children have only responsible adults as their advocates, and cannot reasonably be expected to know that something is wrong with them that they cannot help.  
The symptoms of McArdle’s Disease are subtle but specific.  Your attention and action can mean the difference between years of physical and emotional discomfort, and a more normal childhood.  If you are a physical education teacher who would like to know more about the disease, please contact us for information.