My four year old son has a whole bunch of books in this series. They are all AWESOME. My son really likes facts and history and these books are full of both. You don't read them like a story - rather, they are basically written as one fact after another with lots of exciting illustrations in between. I like that I can jump around from fact to fact or picture to picture, depending on my son's mood or attention span at that particular point in time. He has actually been absorbing many of the names and dates and facts and statistics. I love that these books make it fun for kids to learn! FIVE STARS!!!
High pulls can also be done using a dumbbell or kettlebell,. When doing so, position the weight between your feet and pull with one arm at a time (switching arms halfway through the set). A trap bar (aka, hex bar) is also an option, particularly for individuals who have a hard time keeping the lower back flat; the trap bar allows the hands to be positioned behind the shins to help pull the shoulders back.
A second, more efficient and correct method is to use an infrared laser placed at ground level. When an athlete jumps and breaks the plane of the laser with his/her hand, the height at which this occurs is measured. Devices based on United States Patent 5031903, "A vertical jump testing device comprising a plurality of vertically arranged measuring elements each pivotally mounted..." are also common. These devices are used at the highest levels of collegiate and professional performance testing. They are composed of several (roughly 70) 14-inch prongs placed 0.5 inches apart vertically. An athlete will then leap vertically (no running start or step) and make contact with the retractable prongs to mark their leaping ability. This device is used each year at the NFL scouting combine.