Whether it is high school cross country, a local half marathon, or an ultra-competitive international triathlon, a running athlete's will is always put to the test. Smart science says that to improve long distance running the simple answer is to run more often. While this is true to an extent, ignoring the strength and stamina in particular muscle groups will decrease efficiency and increase risk for injury.
More explosive sports, like football or baseball, require great power and strength from the hips and lower back to generate force and speed. Similarly, soccer players require good endurance from the hip muscles as well as the ability to cut side to side. For long distance runners, who don't need to move laterally or explosively jump, hip muscles are often overlooked. Unlike baseball, soccer, and football, where some strengthening will occur as a byproduct of playing those sports, if a long-distance runner doesn't specifically train their hip muscles, they will not improve simply by running more.
Running 20, 30, or even more than 40 miles a week puts a great deal of stress on the body. As the legs tire, correct biomechanics tend to break down. Weak hip muscles, particular the gluteal musculature, will cause the knee to improperly move inwards and rotate. This increases straining across the knee joint, causing the lower back to tighten and the foot to flatten. Weak hip muscles thus increase the risk of injury to the runner's ankles, knees, and back while making each step less efficient than the one before.
The most important strength and conditioning concept for runners is to train muscles more for stamina than for strength. Being able to lift 300 pounds on a squat bar may be great for a football player but may not offer the same benefit for a long distance runner. Ideally, the hip musculature will be trained to help a runner maintain good pelvic stability throughout their run. This means co-training the core to reduce improper tilting, thus reducing risk of injury and improving overall performance.
Key Exercises
1. Side-lying Plank with Hip Abduction
2. In-Line Lunges with Dumbbells
3. Single Leg Squat.
Remember, conditioning the hips for long-distance running depends greatly on the individual and volume of running. Completing exercises to "feel the burn" may be okay, but pushing through the pain is not wise. The purpose of building stamina with theses exercises is to increase overall endurance with running, not to make it difficult to walk the next day!
Links:
[1] https://mail.momsteam.com/node/5675
[2] https://mail.momsteam.com/team-experts/keith-j-cronin-dpt-cscs/strength-conditioning/single-leg-squats-crucial-exercise-athletic-success