Overtraining: how the right nutrition can help prevent it and keep you on top form!

Where should we draw the line between appropriate ‘heavy training’ and overtraining? And are there specific nutritional practices that can prevent overtraining and accelerate exercise recovery? Mike Saunders explains and shows that these two concepts are intimately linked.

A consistent end result of overtraining is the impairment of physical performance. When you are overtrained, you can expect to see elevated perceptions of exertion/fatigue during exercise, decreased movement economy, slower reaction time and impaired performance times. To make things worse, overtraining status is usually only diagnosed with the benefit of hindsight. In other words, by the time you know you are overtrained, it is too late to handle it effectively!

Overtraining terminology

Recently, the terminology around overtraining has been improved. Researchers from the Netherlands and Belgium have described the overtraining process as occurring in three progressive stages (see box 1)(1):

1. Functional overreaching
2. Non-functional overreaching
3. Overtraining syndrome

Functional overreaching is the normal process of fatigue that occurs with sustained periods of heavy training. Although these periods of hard training cause short-term impairments in performance, this effect is reversed with a relatively short pre-planned recovery period. For example, a 1-week block of hard training may cause moderate levels of fatigue, impairing your peak performance for a few days. However, when you balance this hard training period with a period of adequate recovery, you can quickly return to a level matching and ultimately exceeding your initial level of performance.
Non-functional overreaching is a more severe level of fatigue reached when your performance and energy are not restored after a planned short-term recovery period. This often happens if you work too hard during your recovery days, if you underestimate the impact of the non-training stresses in your life, or if you simply train too long and hard before a recovery period. As a result, you may still feel fatigued following your planned recovery period. This is where flexibility in your training programme becomes very important. If coaches recognise the continued fatigue of an athlete, they can delay the next heavy training phase or competition. This is often enough to reverse the fatigue and restore performance levels.

However, if coaches and athletes ignore fatigue in the non-functional overreaching stage, further heavy training simply results in deeper levels of fatigue. This can become a vicious cycle in which athletes continue heavy training in an attempt to reverse their declining performance, only to exacerbate the problem by further impairing their recovery. True overtraining syndrome is reached only in the most severe cases, and can be quite debilitating. Symptoms of overtraining syndrome overlap with chronic fatigue syndrome and clinical depression, and can only be reversed with several weeks or months of recovery(1).

Balancing training and recovery

The model of overtraining discussed above illustrates the critical balance of well-timed recovery periods within a training program. Your training phases can be specifically designed to cause functional overreaching at strategic times. However, effective training programmes are  created to include adequate recovery to prevent both non-functional overreaching and overtraining syndrome.

As an example, professional cyclists often perform team training camps that provide a significant early-season training stimulus. The volume of training performed at these camps can induce significant fatigue. However, training camps can produce important improvements in performance if the heavy training is balanced with an appropriate period of short-term recovery.

Recent studies from our Human Performance Laboratory at James Madison University (USA) provide some quantitative evidence to support these concepts. We studied professional cyclists who completed at least three consecutive days of high-volume training, averaging almost 100 miles/day. Not surprisingly, the heavy training caused significant changes in a number of overreaching/overtraining symptoms. These included increased levels of mental and physical fatigue, increased muscle soreness and elevated markers of muscle damage.

About half of the cyclists then performed an ‘easy’ day of training on the fourth day – about 30 miles at low intensity. For these highly trained athletes, this was enough recovery to initiate improvement of all of the symptoms mentioned above.

Overtraining and diet

Appropriate nutrient intake and timing can play an important role in influencing the overtraining process. It has long been established that adequate carbohydrate intake is required to maintain muscle glycogen levels during heavy training. This is critical to sustaining high training volumes, as muscle glycogen is a primary fuel stored in muscles and used during endurance training and racing. In addition, we know that exercise stimulates enhanced uptake of carbohydrate in the muscles. This so-called ‘insulin-like effect’ of exercise remains for a short time following exercise. As a result, the consumption of carbohydrate immediately after training (within 30 minutes) produces faster replenishment of muscle glycogen than if carbohydrate intake is delayed. Thus, it is now common practice for endurance athletes to consume a carbohydrate-rich recovery beverage or snack immediately following demanding training sessions.

More recently, scientists have begun to investigate how carbohydrate intake and timing influence specific aspects of the overtraining process. Researchers from the University of Birmingham examined how dietary carbohydrate intake influenced overreaching symptoms during a period of intensified running training(2). When performing 11 days of intensified training consuming relatively low carbohydrate intake (5.4 grams per kilo of bodyweight per day), the runners experienced significant worsening in mood states, fatigue, muscle soreness, and declines in running performance. These factors were considerably (though not entirely) reversed when the athletes performed the same training demands with higher carbohydrate (8.5g/kg/day) in their diets.

The same research group performed a similar study in cyclists(3). Athletes consumed sports beverages with low or high carbohydrate content during exercise (low=2%; high=6%) and immediately following exercise (low=2%; high=20%). When consuming the low-carbohydrate drinks over eight days of intensified training, the athletes experienced significant declines in their mood states, increased perceived effort during exercise, and declines in cycling performance. All of these factors improved when the high-carbohydrate beverages were consumed during/following training.

Following the eight-day period of intensified training, the cyclists received fourteen days of reduced volume training to promote recovery. This resulted in significant improvements in cycling performance (exceeding baseline levels) but only when the athletes drank the high-carbohydrate beverages. By contrast, performance remained suppressed below baseline levels with the low-carbohydrate drinks.

Thus, altering the carbohydrate levels of the cyclists’ sports drinks was enough to influence their responses to training. As a result, the intensified training represented a functional overreaching stimulus when appropriate carbohydrate was provided, but a non-functional overreaching stimulus without adequate carbohydrate. This is an excellent illustration of how ‘optimal recovery’ represents much more than simply lowering the demands of training (see figure 1).

Co-ingestion of carbohydrate and protein

The effects of protein intake on recovery from endurance training have been understudied compared to carbohydrate. As a result, there is no clear consensus among scientists regarding the role that protein plays in the overtraining process. However, recent studies suggest that there may be some additional recovery benefits associated with consuming a mix of carbohydrate and protein following heavy endurance training.

Carbohydrate-protein and glycogen replenishment Combined intake of carbohydrate-protein may influence a number of factors that are important for recovery in endurance athletes. For example, some studies have shown faster rates of muscle glycogen replenishment when carbohydrate-protein is consumed immediately following endurance exercise (compared to carbohydrate alone).

Other studies have suggested that the additional benefits of added protein are negligible if the carbohydrate doses are very high (over 1.2 g/kg). At a minimum, it appears that carbohydrate-protein ingestion is a highly practical way to ensure high rates of glycogen replenishment following exercise, especially when you are not consuming a high-calorie recovery drink or snack. This is particularly relevant in conjunction with the other potential benefits of carbohydrate-protein ingestion discussed below.

Carbohydrate-protein and protein balance Combined carbohydrate-protein intake may also have positive effects on protein balance for endurance athletes. Researchers at Maastricht University in Holland observed that carbohydrate-protein consumption increased protein synthesis and decreased protein breakdown in endurance athletes, compared to when they consumed carbohydrate alone(4).

Investigators at McMaster University (Canada) made similar observations of enhanced protein balance with carbohydrate-protein ingestion following aerobic exercise(5). In addition, they reported that the fractional synthetic rate (FSR) within the muscle was improved with carbohydrate-protein intake (see figure 2, overleaf). Collectively, these studies suggest that protein synthesis in the muscle may be improved with carbohydrate-protein intake. Though the long-term effects of improved protein synthesis and protein balance have not been studied in endurance athletes, this evidence suggests that protein may be helpful in stimulating muscle recovery and promoting positive muscle adaptations following heavy endurance training.



Carbohydrate-protein and muscle recovery Carbohydrate-protein ingestion has been associated with improvements in various other markers of muscle recovery in endurance athletes. For example, researchers from our Human Performance Laboratory at James Madison University have observed that carbohydrate-protein ingestion results in lower blood creatine kinase (CK) levels (an indicator of muscle damage)(6,7), less muscle soreness(7), and improved muscle function(6)following heavy endurance exercise (see Figure 2).We have observed these benefits in carbohydrate-protein versus carbohydrate-only drinks matched for both carbohydrate content and total calories(6). In addition, we have observed these effects when we studied carbohydrate-protein beverages consumed during endurance exercise(6) or immediately following exercise(7). In one study, we examined carbohydrate and carbohydrate-protein recovery beverages during six days of consecutive training in collegiate distance runners(7). While consuming the drinks containing carbohydrate-protein, the athletes had lower blood CK levels and less muscle soreness, despite performing identical training loads between the two periods.

Carbohydrate-protein and subsequent performance

A critical question for coaches and athletes is whether the improved muscle recovery markers observed when consuming carbohydrate-protein drinks relates to any tangible benefits with respect to sport-specific performance. In other words, if carbohydrate-protein intake improves ‘recovery’, does this lead to enhanced performance during subsequent exercise?

Studies investigating this issue to date have produced mixed findings. For example, in our aforementioned study of runners, we did not observe differences in running performance following the six-day training period between the two beverages. However, this was probably due to the fact that the athletes were reducing their training levels in preparation for a race. Thus, they were probably well recovered prior to the race under both beverage conditions.
This evidence leads to an important observation: no supplement can be expected to enhance your recovery if you are already fully recovered. If you only perform light exercise, and take relatively long recovery periods between workouts, then the composition of your post-exercise nutrition regimen is far less critical, and perhaps irrelevant altogether if your regular diet is appropriate. However, if you perform heavy exercise on a regular basis, then it is important that your recovery nutrition includes adequate carbohydrate to maximise your post-exercise recovery. Under these conditions of heavy exercise and short recovery periods, it also seems likely that carbohydrate-protein sustains high performance levels better than carbohydrate alone.

Evidence supporting this concept can be observed in recent studies on this topic, including our study of runners discussed above. As mentioned previously, carbohydrate-protein did not produce performance improvements in runners who were tapering slightly prior to a race. However, the athletes who continued to perform the highest training mileage throughout the six days had the greatest improvements in muscle recovery with the carbohydrate-protein. This same group of ‘harder-training’ athletes also had a stronger tendency towards faster race performance with the carbohydrate-protein drink.

More convincingly, US researchers at the University of California-Davis examined the effects of carbohydrate-protein drinks during a short period of heavy cycling training(8). They assessed changes in blood CK and time to fatigue during three consecutive days of exercise. These variables got significantly worse over the three days of hard training when the cyclists consumed carbohydrate-only drinks. However, these declines were prevented when carbohydrate-protein drinks were consumed.

Similarly, researchers from Canada tested recovery and performance during two 60-minute cycling performance tests, separated by six hours(9). Carbohydrate or carbohydrate-protein recovery drinks were provided immediately after the first exercise trial. The cyclists were able to generate higher power output and better performance in the second exercise session following the carbohydrate-protein beverage, compared to the carbohydrate-only drink.
Not all studies have shown significant improvements in subsequent performance following carbohydrate-protein intake. However, the positive effects of protein seem to appear more regularly in the studies that provide the more demanding training/recovery periods. Thus, the longer and harder you train, the more important the details of your recovery nutrition, including the inclusion of protein, become.

The bottom line

In summary, overtraining is a complex issue, which can have important consequences for endurance athletes. Functional overreaching can be an intended outcome of heavy training periods, provided it is balanced with an appropriate period of recovery. The consumption of adequate nutrients, especially in the period immediately following heavy exercise training, can augment recovery from exercise. Thus, recovery nutrition can assist in the prevention of non-functional overreaching, and allow you to get the most out of your training. In short, this means making sure that your daily carbohydrate intake (especially immediately post-exercise) is adequately high to maintain your muscle glycogen levels during training. In addition, adding protein to your post-exercise recovery drinks and meals appears to have further benefits to promote optimal recovery from heavy exercise.

References

1. Sports Med 2006; 36: 817-828
2. J Appl Physiol 2004; 96: 1331-1340
3. J Appl Physiol 2004; 97: 1245-1253
4. Am J Physiol Endocrinol Metab 2004; 287:E712-E720
5. J Appl Physiol 2009; 106: 1394-1402
6. Int J Sports Nutr Exerc Metab 2008; 18 :363-378
7. Int J Sports Nutr Exerc Metab 2006; 16: 78-91
8. Int J Sports Nutr Exerc Metab 2008; 18 : 473-492
9. J Int Soc Sports Nutr 2009; 5(24)