Probably what is also happening is that there has simply been a reduced exposure to prolonged exercise.

One contingency plan is to alter the flight paths of aircraft and fly them at lower altitudes to reduce exposure to radiation.

Similarly, if a stock is performing well, you should let the stock ride without adding or reducing exposure until the quarterly rebalancing period.

Properties that receive a positive assessment can then be tested to establish the extent of the risk and owners can take measures to reduce exposure.

Long working hours and a trend for children to play indoors on computers have also reduced exposure to sunlight.