Linear speed - Acceleration
If we evaluate the acceleration mechanics from the picture, you can see that the foot strike
position is in front of the center of mass(COM). Which ultimately creates braking and compressive forces on the knee joint. This common error is known as ”over-striding” or ”heel striking” and is a common reason for runners' knee.
An athlete has to be powerful enough to establish and maintain a lower drive angel during acceleration, and the foot placement should be directly under or behind the COM during acceleration.
Here as some tips to fix this:
Try to drive the body out with more forward lean aim for a 45-degree angle
Keep the heel recovery low
Focusing on striking slightly behind your hips
All of these will lead to a better(i.e., smaller) shin angle, steering to more horizontal velocity.
The figure to the right has a smaller shin angle and is striking behind their COM. While the figure to the right has a bigger shin angle and their foot is almost striking in front of their COM and have a bigger projection angle.
During the acceleration phase, we are looking for horizontal velocity. Research has clearly shown that the horizontal component of the total ground reaction force (GRF) is the critical mechanical feature of sprint acceleration performance. Force output can be increased by strength training and then later applied in the field.
Force and acceleration are related to your body mass through Newton's second law of motion.... Force = Mass x Acceleration
The more force you can put into the ground in relation to your bodyweight to faster, you'll accelerate. The best sprinters in the world have a force output around 5x their bodyweight.
Videotaping is a great tool to evaluate your mechanics regardless of sport. By taking the time to assess your own movement, you can increase proprioceptive awareness by being more familiar with your areas of improvement.