THERE is only so much good that you can do to your body with pilates, and other such exercises where lying down features heavily. Those people who rattle on about the importance of &ldquo;strengthening the core&rdquo; really need to know one thing: the only way to get properly fit is to feel some lung-busting pain. And now summer is here, that means running. <br /><br />The City doesn&rsquo;t have particularly easy access to the sorts of green spaces that make for a good, long run, but London is a big and varied place. If you know what you are doing, then you can find top-quality runs all over the place, many of them involving the City and its environs. <br /><br />There are plenty of circular runs that take you all over town &ndash; it&rsquo;s not far on foot to Covent Garden &ndash; and the Thames-side runs offer you some incredible sights. Canary Wharf is even better, offering easy access to the Regent&rsquo;s canal, the river-front, or even around the Isle of Dogs itself, which (lest we forget) takes you through some of the most spectacular architecture in Britain. <br /><br />Here is our pick of the best runs around the City and Canary Wharf. Now there&rsquo;s no excuse to strap on those trainers this lunch-time.<br /><br /><strong>City to Westminster loop: 12km</strong><br />Bank, Mansion House, the Houses of Parliament, the London Eye, Tate Modern. The scenery on this run is second to none, and it can easily be cut short if you don&rsquo;t have the time to go all the way down to Vauxhall Bridge. It can also be extended at the start, of course, from wherever you work in the City. <br /><br /><strong>Canary Wharf loop: 7km</strong><br />You don&rsquo;t have to actually go far to get a proper run in, and this is ideal for a lunch-time work-out. Taking in Mudchute and Millwall Parks, and skirting the riverside on the east side of the Isle of Dogs with views over to the Dome and Greenwich, then taking in the docks, this is a surprisingly varied loop that can be started from anywhere in the Wharf. <br /><br /><strong>City to Covent Garden loop: 7.5km</strong><br />A great one if you are near Barbican/Farringdon, St Paul&rsquo;s or Mansion House, this takes you out of the City over the Millennium Bridge and down to Westminster (if you can fight your way through the tourists at the Eye) and then takes you through Whitehall and up to Coram&rsquo;s Fields and then back down Gray's Inn Road. A real urban run without much green, but you&rsquo;ll see the sights. <br /><br /><strong>Algate and onwards loop: 9km</strong><br />A route that takes in some of the best of London&rsquo;s waterways, including the Regent&rsquo;s Canal and the Thames, past Tower Bridge. True, this is perhaps not the prettiest bit of canal, but this run can be adapted so you can head up the west to Regent&rsquo;s Park via Paddington Basin and the surprisingly pleaProxy-Connection:keep-aliveCache-Control:max-age=0nt route past Kings Cross, or east into Victoria Park. <br /><br /><strong>Barbican loop: 6km</strong><br />A pleasant circular run that takes in the brutalist beauty of the Barbican and the calm of Finsbury Circus, via historic Smithfield Market and some of the more modern glass-and-steel buildings that decorate the City. Coming in at just under four miles, this is perfect for a quick lunchtime booster.