NFL Hall-of-Famer Jerry Rice says hill running is the most effective workout to build stamina, speed, and leg muscles

• Jerry Rice was known as one of the fittest NFL players during his career from 1985-2004.
• A workout Rice used to stay in shape was "hill running" which involves long-distance up-hill runs.

Jerry Rice was known as one of the NFL's biggest workout warriors of the 80s and 90s. The Hall-of-Fame wide receiver's commitment to fitness helped him stay in the league for two decades from 1985-2005 and play at a high level into his 40s.

As a wide receiver, he depended on his speed, and built his reputation on maintaining that speed on long routes late in games when other players started to fatigue.

One workout Rice said he swore by to keep in shape was hill running, which involves running up hill for up to two and a half miles. For the last 800 meters, he would bolt up the steepest slope he could find. The workout is known to help build endurance, lower-body strength, and can increase a person's maximum running speed.

Rice said he and his San Francisco 49ers teammates did hill running three times a week during the offseason, and kept track of their times so they could try to improve each session.

"It gave me that endurance that I needed in the fourth quarter of a ball game," Rice told Insider. "Towards the end I wanted to be at my best so that's the way I trained. That last 800 meters is when I really pushed myself. "

Hill running can improve speed and build muscle

Rice said he learned to do hill running from his teammate and former 49ers running back Roger Craig. Rice said he then passed it onto other players that came after him like Barry Sanders and Terrell Owens, who have both joined Rice in the Hall of Fame.

Regular distance running on a flat surface is one of the best forms of cardio exercises and can help build up endurance, burn calories, and promote good heart health.

While normal running doesn't do much in the way of helping to build muscle, hill running adds resistance to running to make it a lower-body workout too.

The incline specifically builds strength in the calves, quads, hamstrings, and glutes, hip flexors and Achilles' tendons.

The muscles used in hill running are also the same used for sprinting.

One study by Dr. Derek Ferley, director of sports science research and sports performance training at the Avera Sports Institute, found that subjects who trained by running on an incline improved their maximum speed versus subjects who ran on a flat surface. They. were also able to run at their maximum speed for longer distances.