– Derek M. Hansen – February 10, 2009 -
While everyone is clamoring to find the greatest new exercise or supplement for health, fitness and performance, I am always searching for easier ways to do more with less. In short, I am trying to determine the optimal amount of work for a given athlete, without falling into the trap of overtraining them. What is the minimum amount of work I need to create improvement? Call me lazy. Call me a pseudo-intellectual. Either way, it is important to understand that the human body and mind have a finite capacity for stress and work, particularly when you are seeking positive adaptation and consistent improvement. Fatigue has also been linked with a higher incidence of injury which reinforces the need to be working from a position of strength rather than weakness.
Types of Fatigue
Fatigue can be classified in one of three categories: Neuromuscular fatigue, metabolic fatigue or neuroendocrine fatigue. Excessive fatigue in all cases can lead to overtraining syndromes that are detrimental to the athlete whether it is creating an environment for injury or a downward spiral in health and overall conditioning.
Neuromuscular fatigue involves the central nervous system (CNS). Fatigue of the CNS creates a state of inhibition, resulting in slower and weaker muscular contraction (lower proportion of motor unit recruitment). Regeneration of a nervous cell is seven times slower than for a muscle cell. Recognition of this type of fatigue is critical for runners who are training for speed. The ability to recruit muscles for fast action can be significantly impacted by recovery times. Recovery times that are too short negatively impact an athlete’s ability to recover for optimal performance on the next repetition. Repeated bouts of speed work must include appropriate rest intervals to ensure proper recruitment and maintenance of optimal running mechanics.
Metabolic fatigue is related to the depletion of fuel and includes the effects of lactic acid build-up. For high-intensity workouts and performances, continued operation at the upper limits of output will lead to the depletion of ATP-CP stores (short-term fuel supply) and the corresponding building of lactic acid. Hydrogen ion accumulation interferes with the production of ATP and the increased acidosis inhibits binding of calcium ions with troponin, thereby affecting muscular contraction. This process also creates discomfort, affecting psychological fatigue and tolerance. For longer duration efforts, fuel in the form of free fatty acids and glucose will eventually become depleted as well.
In neuroendocrine fatigue, the prolonged stress of training impacts hormone levels, including adrenaline, noradrenaline, human growth hormone, cortisol and thyroid stimulating hormone. As fatigue persists and hormone levels are altered, so is the function of the autonomic nervous system, resulting in overtraining symptoms. For high intensity sports (i.e. sprinting and heavy weightlifting), persistent fatigue leads to thyroid hyperactivity, affecting the sympathetic pathways of the autonomic nervous system (i.e. “fight or flight”). Testosterone to cortisol ratio is disrupted in favor of cortisol, resulting in a catabolic state. Key symptoms of high intensity overtraining include:
- Increased heart rate
- Decreased appetite
- Reduced recovery after exercise
- Disturbed sleep
- Increased resting blood pressure
- Increased incidence of infections
- Decreased maximal power output
- Decreased performance
- Weight loss
- Increased irritability
- Increased emotional instability
- Loss of training and competitive desire
- Postural hypotension
- Increased incidence of injury
- Decreased plasma lactate levels during exercise
For endurance sports, high levels of fatigue and prolonged overtraining from too much volume can affect the parasympathetic pathways of the autonomic nervous system (i.e. “rest and digest”). It is the result of diminished activity of the adrenal glands. This type of overtraining is difficult to detect early, due to the absence of any dramatic symptoms. Key symptoms of overtraining as a result of excessive volume in endurance sports include:
- Progressive anemia
- Decreased hemoglobin
- Decreased hematocrit
- Need for more quality sleep
- Low blood pressure
- Low resting pulse rate
- Decrease in free testosterone level
- Mood state disturbance
One of the keys to consistent improvement in performance is the ability to identify fatigue early and make adjustments to training to ensure recovery and successive loading is optimized. However, sometimes overt signs of fatigue can be detected only after it is too late. Some of the best coaches are able to anticipate fatigue based on their vast experience or subtle cues that they pick up from the athlete. Keen observation is the best tool you will have in your arsenal to determine potential signs of fatigue. While it would be nice to have lab test results at our fingertips on a weekly basis, it is not practical or affordable for most athletes. And, by the time you get the results back from blood work or similar tests, it is too late to implement an intervention. Simple strategies for identifying signs of fatigue before problems arise in the form of overtraining, injury or illness are provided below.
Reductions or Plateaus in Performance
The stopwatch is the coach’s and the athlete’s best indicator of fatigue and overtraining. I am amazed at how many athletes are perplexed by poor times when they are putting in so many hard hours of training every day. I say to them, “If you are working hard all the time and you aren’t improving, what must be the problem?” Many times they are unable to give me a good answer. They question their will, their training philosophy and even their equipment. Very rarely will they admit that they are tired and overworked. We have all experienced having an injury or illness, then coming back to the track and having better than ever performances. The only explanation for the improvement must be excessive fatigue remedied by appropriate recovery and regeneration. If the stopwatch indicates that performances are lacking and you are training diligently, inserting more rest may be the answer.
Deterioration of Biomechanics and Technique
A gradual reduction in the quality of running technique may be a sign of apathy on the part of the athlete, but in most cases it is a clear sign of fatigue – particularly if it occurs toward the latter stages of the workout. For runners, postural changes and foot-strike anomalies are some of the key areas of evaluation for a coach. As the athlete fatigues, whether it be a sprinter or a longer-distance athlete, the hips will be pulled down closer to the ground by the forces of gravity. The amount of knee flexion will increase as well as ground contact time for each stride. Improper foot-strike will also be made obvious by the audible sound of heavy foot-falls. A tired runner will plod, while a fresh runner will make less noise on ground contact. Constant evaluation of technique is critical for a coach, whether it be through real-time observation or periodic review of video footage of the athlete, comparing against baseline video when it was obvious the athlete was fresh.
Evaluation of the Athlete in Different Environments
I highly recommend weight training for runners. Not only does it provide useful strength gains that transfer to the running action, it also provides you with another means of evaluating the status of the athlete. Weights provide a quantifiable measure of performance. Either you can lift a given weight, or you cannot. If fatigue is an issue, it will show itself in an athlete’s lifting performance. Other simple evaluations can be done to determine levels of fatigue or overall preparedness. Something as simple as a periodic vertical jump test – which doesn’t take a lot of energy to implement – can provide you with ongoing information on the status of an athlete.
Massage must be performed on athletes on a regular basis to determine the status of muscle and connective tissue. Passes over a muscle can determine status of muscle tone. In some athletes, excessively high muscle tone is a sign of high workloads and inability to recover appropriately. In other athletes, very low muscle tone can be an indicator of excessive fatigue and lack of preparedness. I have worked with athletes who think they are recovered, but when they get a thorough massage on key muscle groups, they can’t believe how much soreness and stiffness they actually feel in their muscles. The “hands-on” method will determine where key problems exist in the musculature and soft tissues. For athletes that don’t have access to a trained massage therapist, self massage with simple passes over key muscle groups will help determine problem areas that can be addressed through further massage, static stretching or work with a foam roller.
Use of Technology to Determine Recovery Status
Significant advances in the study of Heart Rate Variability (HRV) have allowed us to have a deeper look into the physiological status of an athlete through non-invasive means. HRV has been used outside of the athletic realm for determining the stress levels and health of patients at risk for heart attack or those recovering from cardiac arrest. More recently HRV has been used for determining the recovery status and preparedness of high performance athletes. HRV involves the measurement of the time interval between heartbeats (the R-R interval). One would think that a healthy heart beating at a rate of 60 beats per minute would have equal inter-beat time intervals of one second. However, healthy individuals exhibit greater variability between individual heartbeats than those who are stressed or at risk for heart attack. While one interval may be 0.85 seconds, another one may be 1.15 seconds in a healthy athlete. The autonomic nervous system (ANS) controls the beating of the heart and any disturbances in the ANS (i.e. stress and fatigue) will affect HRV and can be detected by HRV analysis. An advanced heart rate monitor – such as the Suunto T6C – will allow you to effectively record R-R interval data for analysis of HRV. I will devote more time in a future article on the use of HRV for monitoring athlete recovery and preparedness.
Communication and Documentation of Athlete Status
Many of the strategies presented above are non-verbal in nature. However, simply talking to an athlete about how they feel can reveal much about their training status and levels of fatigue. Coaches need to engage athletes on not only training status, but other aspects of their life, including appetite, sleep, academic performance and relationships. This information can also be documented in training journals that can be reviewed by the athlete and coach on a regular basis. All information must be reviewed as a collection of data – verbal and non-verbal – in an effort to determine the status of the athlete.
Once unwanted fatigue has been identified, action must be taken to ensure the athlete recovers appropriately. In the next installment of this discussion on Fatigue Identification and Management, we will address key methods of hastening recovery and incorporating appropriate rest and recovery methods. This will included making adjustments to a training program to avoid excessive fatigue, as well as implementing pro-active methods of facilitating optimal recovery.