There are a few things to consider when deciding on what type of assistance exercises to use. The first is selecting the relevant muscle groups that must be strengthened. The second is to determine the movement time and the rate of forced development that matches the sports skill. Third is to select the type of resistance exercises that address the movements encompassed in the sports skill. And fourth, is to choose the velocity that best matches the sports movement. Number five, is to determine if the posture used in the resistance exercises matches the posture when performing the sport skill. And finally, number six, is the direction of movement. And we're going to now discuss each of these six elements here in a bit more detail. We'll begin by selecting exercises that target relevant muscle groups because this is really important. Sport skills combines the coordination, strength, and power of many muscles. They don't just isolate one. And the assistance exercises must target the actions these muscles perform. For instance, a hurdler needs strong hip and knee extenses that can move quickly. One resistance exercise matching this requirement is the snatch and the muscles-in-motion software allows you to explore what muscles different types of exercise target. The software also provides instructions on how to perform the lift. For example, the snatch involves three components. The coordination of two pulls and there's a full body extension and jump and then, there's the drop and the snatch component. The first pull targets the quadriceps femoris muscle and the action is knee extension. The second pull targets the gluteus maximus muscle, the big butt muscle at the back. And this action is hip extension. The jump after the second pull targets all the key muscles of the leg, the hip and the upper back. And I've got these muscles highlighted in red here and include the gluteus maximus, the quadriceps femoris and the gastrocnemius. The upper trapezius elevates the scapula. And finally, the drop and catch phase targets the muscles important to resisting the force of gravity when the athlete's foot hits the ground after hurdling and running, after the hurdling and the running flight phases. And once again, these muscles are highlighted in red. The snatch is a really excellent exercise for training neuromuscular timing and coordination in addition to training strength and power of muscles relevant to hurdling and many other sport skills incidentally. Using the snatch is much better than training each muscle individually because it trains muscle synchronization. And in this way, there is a more effective training transfer effect. Now, rapidly developing wearable technology permits the average athlete now to gain a fairly clear picture of the muscles they're using. The muscles being used to maintain this posture are highlighted here in yellow. And when the athletes muscles activate, they emit an electrical signal and micro-sensors that are woven into specially designed clothing pick up these signals that are coming from these sensors. A tiny Bluetooth device transmits the data to a smart phone. And if you don't have the muscles-in- motion software or a similar product, or access to wearable technology, any anatomy book will describe the action each muscle in the body performs. You can also seek research on the muscles you used in a particular movement. Personally, I believe this would be a valuable service. The national sport organizations could provide a coach.