Do resistance training for running improvement. Focus on leg exercises that strengthen weak or injury prone areas of the body. Squats, lunges and step-ups help with strengthening the quads, hamstring and muscles around the hip. This will prevent injuries and help you run faster and longer.
The arms help counterbalance your legs, keep the torso more stable and provide propulsion while running, especially up-hill and at faster speeds. Look at sprinters, they have big shoulders to drive their arms for extra acceleration. Do shoulder raises and bicep curls to improve arm carriage.
The core including the abdominals and back help keep an erect upright posture. Most runners are too hunched over especially when becoming tired. Doing back extensions and crunches will help maintain an efficient posture for longer. These muscles also help you breathe easier while running.
Do lunges as a running warm up as well as part of your strength training routine. Lunges are the best exercise for runners. It replicates the running stride and works the same muscles very closely. Use it as a dynamic stretch to warm up before your run to help warm up the legs. 20-30 lunges will achieve this.
Running up hills is a poor man strength workout. You don’t need any fancy equipment just a big hill or some steps. Do interval training. Run up the hill then walk or jog back down. Repeat. You build up the muscular endurance of the thighs and calves this way, as well as improving cardiovascular fitness.
Prevent injuries by stretching everyday. A functional muscle is one that is long and strong. If any muscle group is tight it will most likely become injured. Focus on these tight areas especially. For most people this includes the hamstrings and calves. As well as stretching use a foam roller to roll over on your problems areas. Every runner should use a foam roller to massage any tight niggly areas to increase functionality. I recommend using a heat pack on problems areas, rubbing on an anti-inflammatory gel then using the foam roller to massage out knots.
Do specific training for your event. 10km or shorter is more anaerobic so you should be focusing on shorter, faster and more powerful training. In the gym do less reps and more weight. Marathons are more aerobic so exercises should be longer and based on endurance and strength. Have less breaks in-between intervals or sets to replicate the consistent intensity of a marathon.
Feet and lower limb strength is important for longer events. Wobble board exercises will strength the ankle joint and increase balance. While calf raises will prevent muscle cramping while running. The feet take a real pounding while running so do exercises to strengthen the arches. Picking up marbles with your feet are a fun way to accomplish this.