Most physical activity, even for an active person, only exercises the body in a very finite number of movement patterns.
The problem with is that weak spots develop which are vulnerable to unexpected movements and actions. Many injuries are caused by this.

Here are some thoughts on patterned movements

• The best training for any sport is the sport itself -- but in the off season / off
  peak time, mix it up a bit and challenge yourself;
• Even in multi-sport there are limited movement patterns so try some
  activities you haven't done before and get good at them;
• Modern society is ridiculously "safe" and with home, office, streets and parks
  being dead flat your nervous system becomes dull;
• Regularly exercise on unstable environments such as sand, rocks, in water,
  on balance beams, Swiss-balls, wobble boards, climbing etc;
• Work based fitness is probably unequaled in physical benefits and the
  manual labourers of the past were often in very good shape..