Walking is the ideal exercise to start with, rather than running, long periods of cycling, etc. Swimming is also a safe sport to start with, particularly for anyone who is overweight. You may often hear that walking is not strenuous enough to have any effect on stamina. But that’s not true. Complete beginners do gain a training effect from this type of extended activity.
Beginners must also focus on building up stamina. Speed, power, suppleness and so on are aspects that can be tackled later, once the individual has built up their stamina.
A golden rule is that beginners should not get out of breath. If you become out of breath, during cycling, swimming or running, for example, this signifies a higher intensity than is strictly necessary to build up fitness.
Even experienced athletes generally train without getting out of breath. This level of exertion cannot be sustained for long periods, particularly if you’re a beginner. A good benchmark for assessing pace is that you should be able to talk while exercising.