I am writing this for the benefit of the hundreds of cyclists I see every month suffering because of at least one of these three basic and easily rectified problems:
1) Pump up your tyres. The rolling resistance of a tyre not inflated to its rated pressure (usually printed on the tyre sidewall) is much higher than if it were properly inflated. If you are finding cycling generally knackers you, check the tyres. It is also worth noting that a tyre will feel hard before it reaches its rated pressure. If your pump has a gauge make sure you get the pressure to at least the minimum quoted on the side of the tyre.
2) Raise your saddle. Again, if you are finding cycling tiring, especially around the knees it is likely that your saddle is too low. When people are new to cycling they usually want that saddle low enough so put both feet down on the ground. When you get more confident, it helps to raise it to the point where your leg is almost straight when the pedal is at its lowest position. This is the height at which your legs are most mechanically effective, allowing you to put more power down, eliminate knee strain and not get so tired. It is also worth making sure the right part of your foot is on the pedal, ideally you want a bit of toe to overhang but not the rest of your foot
3) Use your gears. there are plenty of fixed gears and single-speeds in Manchester, and that is fine (although I see a lot of fixed gears being pushed along rather than ridden). What is more common is people on derailleur-geared bikes who always cycle in the same gear, usually the highest gear or oddly the small-small chainring combination which isn’t a combination you are supposed to use. I notice them overtake me whilst at the front of a queue at the traffic lights. I then have to go around them as they struggle to accelerate in the highest gear the bike has. You will fly off at speed from lights and also climb hills with ease if you are just willing to give the gears a try. It is also worth noting that cycling at a higher cadence (revs per min) is easier in the long run due to the aerobic nature of this kind of exertion versus the generally more anaerobic nature of pounding slowly in a high gear.
To those who are suffering from all three of these conditions, I salute you for not having given up on cycling just yet.