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Most walking races are on the flat or something pretty close to it, so why do we do training on hills? 3 reasons :
To encourage a strong walking action. For people who don’t do resistance training, the fact that you have to use a walking action to push your bodyweight uphill is resistance training in itself. It will result in improved strength in the muscles that propel you along, and this can be translated into faster speed and better resilience to injury.
For people who DO do resistance training, in the gym or wherever, often strength gained in the gym does not directly translate into walking speed. If you do squats, for example, each ‘push’ in the exercise will take between half a second and a second depending on the weight. In race walking, your foot is on the ground and your leg is working for about a third of a second, or less, each time – a much shorter period – so squats do not directly train the fast, powerful response that your muscles need in the athletic movement. Hill work provides a way for your gym-gained strength to be made useful in walking.
Aerobic capacity – the ability of your lungs, heart and blood vessels to deliver oxygen to the working muscles. Any runner knows that going uphill is the surest way of getting themselves to breathe deeply and get their heart rate up to its maximum. Runners can also run hard on the flat to train at close to their maximum heart rates, but this is more difficult for race walkers – the need to keep a legal technique and the buildup of lactate make it difficult to get to and stay at the speeds that work your heart and lungs the hardest.
Working on hills, however, allows you to do this.
Technique. Going uphill requires you to have the ability to straighten your knee a fraction earlier than you otherwise would have to, as the road is coming up to meet you. You also have to use your hips and calves a bit more to keep your drive going as the road is falling away behind you. Going downhill, you have to reach downwards a little with your heel in order to make contact early. All good stuff for improving the reliability of your technique and using all the available muscle power to keep yourself going.
But there are some dangers in hill training for walkers. You need to have a good basic technique. If your knees tend to bend, or you tend to lean forward, you will find that going uphill will tempt you to worsen these faults in order to make the hill easier. You will need good concentration to avoid this! And for everyone, your technique changes slightly when you go uphill or downhill. A widespread view is that walkers should avoid training on hills with a gradient of much more than 1 in 20 – otherwise the changes it imposes on your technique are just too much. And it is of course strenuous training, possibly putting greater demands on the hamstrings, glutes, calves and (on the downhills) shins than they are used to. So to avoid injury, it’s best not to do too much, too soon, and to progress gradually, until your body is used to it.
Did you read the disclaimer?