Being tired is the most common complaint of human kind. This should be no surprise, since an entire industry of “energy drinks” has spawned over the past decade to combat this feeling of fatigue. Fatigue, more specifically, can be defined as a decreased capacity to produce force, reversible by rest. So fatigue really sets in immediately during exercise, as your ability to produce ground reaction force (GRF, see Sparta Point 1/27/10) is incapable of being replicated at the same, initially high level. So our goal should not be to eliminate fatigue, an impossible feat, but rather reduce its inevitable effect on declining performance.
There are 2 major forms of fatigue, peripheral and central. Peripheral fatigue occurs at, or further downstream from, the neuromuscular junction, the point at which the neuron activates muscle. Central fatigue, on the other hand, occurs upstream, from areas of the brain that cause a VOLUNTARY reduction of muscle activation. So central fatigue general occurs from low motivation (see Sparta Point 3/29/11) and continuous submaximal activity, which is yet another reason to avoid those long jogs and cardio exercise at all costs (see Sparta Point 7/21/10). Therefore, our focus will remain on peripheral fatigue as this is the most common contributor to being tired.
We know that fatigue is an inability to maintain GRF, but we can be more specific. The body behaves like a spring, with multiple springs within it (muscles, tendons, joints) so fatigue is really the body’s inability to regulate the stiffness of these springs (see Sparta Point 1/28/09). So stiffness is no longer the bad guy for our aches and fatigue. In fact, stiffness is important; as it allows the body to regulate the springs’ behavior. Just think about an athlete’s knee collapsing inward towards the end of game or match because fatigue has caused a lack of body control…or stiffness!
The initial peripheral fatigue and stiffness deregulation is due to metabolic factors: the accumulation of waste products from exercise. The good news is that this metabolic fatigue resolves an hour or two after exercise! However, there is a major secondary increase due to another peripheral fatigue factor, inflammation. You know how your soreness after a big workout is greatest 2 days later? This soreness, also known as delayed muscle soreness (DOMS), peaks at 48 hours, due to muscle damage and subsequent swelling. This swelling can cause smaller nerves to prevent communication with muscles, eventually limiting force production.
We use our force plate to monitor fatigue, particularly seeing decreases in athletes’ LOAD, or rate of force development. This is a great measure of their stiffness regulation. Without a force plate, some quick tips to limit fatigue and its effects on your workouts are
Back to back days of training are probably better than a day in between, avoiding the dreaded 48 hour soreness peak, which will still happen UNLESS YOU…
Measuring volume of training, particularly high intensity skills like sprinting, to avoid excessive inflammation and subsequent fatigue (see Sparta Point 7/6/11)
Daily myofascial release, or “rolling out”, water and an anti-inflammatory diet (no processed foods but a focus on Omega 3s and vegetables) can help reduce the swelling from post workout.
Another option is to just to keep chugging energy drinks, that hole you keep digging will eventually lead you to stop…when you hit bottom.