This is a good explanation from Hunter's Friend. If you're interested in some good information on bows and arrows you should check out their site.
The "V" shape formed between the two halves of the graph is commonly referred to as the "valley", which represents how quickly the bow transitions to and from full let-off. A bow with a narrow valley is quick to "jerk forward" if you relax too much at full draw. On the other hand, a wide valley bow allows a little more leeway for shooters who tend to creep (a common shooting-form flaw). Aggressive hard-cams tend to have the most narrow valleys since delaying the let-off allows additional energy can be stored during the powerstroke. But be advised, managing a narrow valley bow takes a little getting use to.
If you're accustom to an older soft cycle bow, an aggressive narrow valley cycle may be a little nerve-racking at first. Very aggressive cams can have valleys that are effectively less than 1/2" wide at full draw. This can cause creepers to jerk and flail awkwardly at full draw, since the holding weight abruptly changes if the bow isn't held firmly against the stops. So to avoid being sucked thru your Whisker Biscuit, be prepared to make some moderate changes in your shooting form if you elect to go with an aggressive cam bow.
CAUTION: If you draw a high let-off bow without an arrow on the string, make sure you have a firm grip. High let-off bows are easily dry-fired. Once you draw the bow back and begin to relax, you're likely to forget that the full 70 lbs is waiting for you, just an inch or two away. When you begin to let the bow down, your grip is too relaxed, and WHACK! DRY-FIRE! Dry firing a bow is not only dangerous to the shooter, but it is an ideal way to seriously damage your expensive compound bow and generally voids most manufacturer warranties.
best way to show you valley is shoot an elite then shoot something else you will be able to see the difference in VALLEY immediately you have to almost push the string forward when letting down the bow it does not try and take off when at full draw and relaxed
A forum community dedicated to bow and crossbow owners and archery enthusiasts. Come join the discussion about optics, hunting, performance, troubleshooting, styles, reviews, accessories, classifieds, and more!