It's an activity he loves, but the senior admits, being on the field is grueling.
"It's not a sport for everybody. I mean, it's definitely tough to be as competitive and aggressive as you need to be so, it's exhausting."
Demanding sports are shedding light on the risk of sudden cardiac death.
It's something staff at Advocate BroMenn Medical Center are taking action to prevent.
"The risk is increased three to four time if you're participating in athletics. Especially football and basketball," explained cardiologist James McCriskin.
McCriskin is working to detect heart conditions in students.
A new cardiac screening program called "Advocate for Young Hearts" is letting medical staff do that.
"I probably wouldn't have gotten a test done if we didn't have this here at the school," said Kjeldgaard.
Nurses are doing free EKGs and echocardiograms at Central Catholic High School.
They're looking for irregular rhythms, which can be caused by an electrical defects in the heart.
"The ventricle of the heart should be squeezing to squeeze the blood to the rest of your body. When it's fibrillating it's just quivering," explained McCriskin.
"I have to re-do the test. Again, I think I had something, it was different with the heartbeat," said Kjeldgaard.
But by finding issues now, and treating them, staff say future tragedies can be avoided.
"Central Catholic has been hit by a number of their students who graduated and had sudden cardiac arrest in their early 20's and when you look at that information, they may have been picked up on a screen of an EKG," McCriskin explained.
Lucky for Kjeldgaard, his second test came back clean.
Which gives him peace of mind that his life, just like his heart, will keep ticking along.
Advocate for Young Hearts plans to test students in the tri-county area.
Nearly 400 students were screened at Central Catholic High School Friday.