Human life seems fragile at times – people have been killed by seemingly innocuous objects, like bales of hay, lava lamps, beach umbrellas, and cans of whipped cream.

But many people have tested the boundaries of human ability and resilience – some intentional, some accidental – and lived to tell their stories.

You likely have heard that generally speaking, humans can survive three minutes without air, three days without water, and three weeks without food (the "rule of threes").

Actual limits to human survival have not been established for obvious reasons – it isn't exactly ethical to test how long people can survive without sleep, water, air, or food.

However, we can learn from people who HAVE survived incredible events and lived to talk about them.

Humans are capable of fascinating, incredible accomplishments.

Humans are capable of astounding feats, including some that seem to defy everything we know about the body. Consider the following documented athletic achievements:

Sprinter Usain Bolt is currently the world's fastest human, with a top speed clocking in at 27.8 miles per hour.

Freediver Herbert Nitsch descended 702 feet into the waters of Greece – a holder of 33 world records, he can hold his breath for more than 9 minutes.

Aleix Segura Vendrell held his breath for 24 min 3.45 seconds, setting a world record (and beating the previous record, which he also set).

Strongman Zydrunas Savickas has squatted and deadlifted 955 pounds and 903 pounds, respectively.

Annette Fredskov, who has multiple sclerosis, ran 26 miles a day – every day – for a year. On the last day, she ran 52 miles.

Rock climber Alex Honnold scaled the nearly 3,000-foot vertical rock formation known as El Capitan in Yosemite State Park without using ropes or other safety gear.

Dean Karnazes ran 350 miles straight – which took 80 hours and 44 minutes – without stopping to sleep or eat.

"Iceman" Wim Hof ran a half marathon above the Arctic Circle on his bare feet and stood in a container while covered with ice cubes for more than 112 minutes.

At age 64, Diana Nyad swam 110 miles (between Cuba and Florida) in 52 hours, 54 minutes, 18.6 seconds.

Athletes aren't the only people who have done impressive things.

Every once in a while, you hear about a person who has done something that seems to defy all odds.

Here is a compilation of incredible human accomplishments and tales of survival.

Firefighter Chris Hickman lifted an SUV 12 inches off the ground in 2008, allowing other rescuers to pull a pinned woman to safety.

Roy Sullivan, a park ranger in Virginia, was struck by lightning seven times – the most on record.

The heaviest human ever was Jon Brower Minnoch, who weighed an estimated 1,400 pounds.

Juliane Koepcke survived an ordeal that some call a "double miracle":

On Christmas Eve, 1971, an airplane departing from Lima, Peru, was struck by lightning and broke apart midair. The accident killed every person on board, with the exception of one…a teenage girl named Juliane Koepcke. It was a miracle that she survived the plane crash, but she still needed a second miracle to help her survive alone in the dangerous Amazon rainforest. She got it. After eleven days in the rainforest and overcoming terrible conditions, Koepcke was rescued. Most people never encounter one miracle in their lifetime, but in the span of a week and a half in 1971, Koepcke experienced two miraculous survivals. (source)

Harrison Okene was the sole survivor of the Jacson-4, a tugboat that overturned after being battered by heavy swells off the coast of Nigeria in 2013. Eleven other crew members died as the vessel sank 100 feet down. Okene survived for 60 hours in a 4 square foot air bubble. Here is the incredible footage of Okene's rescue (watch closely beginning at the 5-minute mark – you will see the Okene reach out to grab the rescue diver's hand).

What are the extreme limits the human body can handle?

While science and medicine have done their best to tell us how much our bodies can handle, there are people who have experienced events that seem to challenge those parameters.

Some intriguing examples involve body temperature.