Life is full of uphill and downhills so is running. Expect that in running downhill are nicer than real life.
Correct form to run uphill
Running uphill can improve overall running technique and develop strength if it performed the correct running form. You should not lean forward on your waist, as you close hip flexors and not left enough space to lift a leg. Of course, there will mild forward leaning but many runners lean too much. Feet should land more mid/forefoot and ankles and calves working more than normal running.
When moving the forward to drive phase you should extend the leg behind you to produce energy and activate glutes. If you lean forward you feel more unstable and straightening the leg coming more difficulty.
Correct form to run downhill
Here again, runners often lean too much backward, which slows you down, which is good as it prevents you from landing on your face, but too much is too much. Feet should land on your heel and feet should land below of your centre of mass.
Downhill increases your speed, which means you have increase cadence. You can modify your speed on your leaning if the hill is steep and you want to slow down, lean more backwards. You should always feel the control or you feel soon find yourself on the ground. If you suffer shin splits avoid downhills, as long as you are fully recovered.
Why hills are important?
Uphill and downhill running impact also running biomechanics, there are changes in joint kinematics and impact shock, strike pattern and reaction forces (Vernillo, G., et al.). Giving a different kind of stress to the body than flat running develops physical fitness.
Hills increase strength and power, running form, cardiovascular boost, oxygen uptake and endurance. Don’t forget the downhill, we often only do uphills and walk downhills back to down. Downhills increase the range of motion and foot speed and overall speed as well.
Dumke, C.L. and his colleagues (2010) find in their studies that muscle stiffness is significantly related to running economy at a speed that approximates endurance competition. When muscle stiffness increase, less muscle activation is required, so energy expenditure is spared. They used maximal isometric squat test and maximal countermovement jump to test muscle strength, but as we already stated that hill running increase muscle strength it’s in connection with running economy.
Hills also give a variance for your training, don’t skip them. If you have to avoid hills up to this point, add them to your training, start easily, short and gentle hills, do a couple repetitions. When you become more comfortable with hills and your strength level increases, add more reps and head longer hills.