Before you begin ... and after you've finished  Whatever your
fitness level, warming-up and warming-down is crucial. Christian
Malcolm and Steph Twell show us how it's done   • The Guardian,
The warm up  The warm-up has two main purposes:  1. To gradually
raise your heart rate, which enables the heart and lungs to
supply oxygen to the working muscles efficiently.  2. To raise
body temperature, which makes the muscles more pliant and joints
mobile, allowing better movement and reducing the risk of
injury.  What to do  The general rule is, the more demanding and
intense the session, the longer the warm-up. Sprinters can spend
an hour or more warming up - not only working on raising heart
rate and body temperature, but also honing neuromuscular
pathways (the link between the muscular and nervous systems),
thereby increasing the speed and efficiency of muscle
contraction.  The general rule is, the more demanding the
session, the longer the warm-up. For a steady run, you could
simply start at slow jog and work up