As virtually every professional bettor will tell you, backing heavy favourites is a sure fire way to the poorhouse. That's common knowledge, right? Perhaps, but there's one problem with that sort of thinking: it's dead wrong.

The received wisdom will be the linesmakers skew their odds on heavy favourites because the public love betting on the very best teams. The bookies undoubtedly see a flurry of parlays involving clubs like Chelsea, Barcelona and Juventus every weekend. Surely there is value in taking the underdog in these situations, is not there?

Actually, numerous studies have shown that blindly backing long shots is a losing proposition in the long-term. To view why which is the situation, we have to know how a bookmaker operates. Since the bookies take most of their action on short-priced favourites, great online gambling it's often assumed they can be exposed to big liabilities if all of the hot teams win. Although this is sometimes the situation, and several bookmakers suffer months of huge losses, you will discover a few ways a bookie can protect himself.

You need to understand that most heavy favourites are combined in parlays involving at least three teams. A bookmaker only needs one loser to take his customer's money. So, there is little need to lower the odds on a "public" team. Many sportsbooks will even inflate the odds of a hot favourite to attract new customers, safe in the knowledge that parlay players won't hurt their bottom line.

Should the favourite's odds are an accurate reflection of it's true probability of winning, the bookmaker must make adjustments elsewhere. That usually means offering worse odds on the underdog and also the draw. Understanding the concept of theoretical hold can make this clearer.

When creating lines, a sportsbook shall offer odds on each team which give it a slight edge, ensuring a profit however the game turns out. This is called the Theoretical Hold and is expressed as a portion. It represents the combined amount of customers' bets that the bookmaker expects to keep.

It's called theoretical because in reality a bookmaker rarely has balanced action on all sides. If a bookie takes the majority of his bets on a heavy favourite, he can offer it at a more generous price and accept a smaller profit margin. Short-priced favourites generally have small margins, but high volumes. Bigger odds mean bigger margins. There is little incentive for a bookie to offer competitive odds on a big underdog if he will not expect much betting interest in that team.