Vitamin C

One thousand milligrams of vitamin C, split into two 500 mg doses per day, can help battle chronic fatigue and increase your leg muscles’ endurance. This may be in part to the vitamin’s effects on adrenaline and cortisol in your muscles, as well as its anti-inflammatory effects. In a 2001 study published in the International Journal of Sports Medicine, researchers noted that vitamin C supplementation in ultramarathon runners helped increase the presence of anti-inflammatory substances in the runners, as well as reduced stress hormones — all factors that may lead to faster recuperation and increased energy.

Vitamin B12

Vitamin B12 helps with the conversion process of fat and protein into energy. Thus, it’s often used by athletes to increase energy levels, enhance performance and build endurance. The U.S. Office of Dietary Supplements warns that a deficiency in this vitamin — the average adult needs 2.4 mcg a day — can directly lead to weakness and fatigue, both in your legs and the rest of your body.

Vitamin D

When you turn your face up toward the golden sun, you get not only a dose of warmth, but also a boost of vitamin D. For runners, vitamin D can help reduce muscle pain and can also help battle chronic fatigue, reports Men’s Fitness magazine. Other benefits for your leg muscles: it may help reduce inflammation — perfect after a strenuous leg workout — and boosts immunity. Additionally, a 2009 study in the Medicine & Science in Sports & Exercise medical journal notes that vitamin D improves general athletic performance by increasing the number and size of muscle fibers in your legs and elsewhere. The average adult needs 600 IU of this vitamin daily.

Pantothenic Acid

Pantothenic acid, also known as vitamin B5, is critical for your energy production in your legs and the rest of your body. For this reason, it’s been used to treat everything from fatigue to muscle cramps. Many runners and athletes don’t get enough B vitamins in general; aim for 5 to 10 mg of vitamin B5 a day.