Category: Nutrition

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Electrolytes – How to Save a Stack of Money Including Your Health

Without going into a long story here, suffice it to say that cancer has forced me to take a long and hard look at a lot of what I’ve done in the past, and institute many changes in my approach to nutrition and sport supplementation.

In a nutshell, most important amongst these are the dietry exclusion of all processed and added sugars (sucrose, dextrose, fructose, glucose etc), dairy and processed foods (everything in a packet, bottle, box, tablet, capsule or powder), and the almost exclusive inclusion of fresh raw fruit and vegetables, and only cooking fish, meat (no beef unless grass fed, and pork), poultry and eggs – all organic, free range and grass fed!

Back to nature!

This has posed some special sport challenges with regard to event nutrition, and my current solution is to ditch all the energy drinks, bars and gels, and replace them with Liquifruit (It is pure fruit juice with no sugar, preservatives, flavourants or colourants) diluted 1 to 2 with  rainwater or Tsitsikama Crystal bottled water, and organic dates from Woolworths for longer rides.

What remains is to ensure sufficient electrolytes replacement. I am not happy with the commercially available products, as they all contain processed dextrose, and most have flavourants, colourants or preservatives added. Plus they cost a pretty penny!

So here is the solution:-

The following powders can be bought from Natures Own Pharmacy in PE, or ask your local pharmacist/ health shop.

400g Sodium Chloride – Himalayan Salt (best) comes in 1kgs (R45.00)

500g Sodium Bicarbonate – comes in 500g (R29.00)

300g Potassium Chloride – comes in 500g (R50.00)

DO NOT BUY SODIUM BICARBONATE FROM A REGULAR GROCERY STORE AS THESE CONTAIN EXTREMELY HARMFUL ALUMINIUM BASED AGENTS. ONLY USE CERTIFIED PURE PRODUCTS FROM A HEALTH SHOP.

Thorughly mix these powders in the proportions given above, ensuring any lumps are completely broken up.

Put 2.5 to 5.5g (half to one level medicine measure) in your 750ml bottle with diluted Liquifruit (if not fat adapted) or just plain bottled/rain water.

This should give you plenty electrolytes for at least 400 water bottles at a total cost of R125.00, compared to R3600.00 for the equivalent in “Rehidrat” which retails at around R9.00 per sachet (all prices at time of writing)!

Of course you may only need to worry about taking in extra electrolytes during sessions that exceed 1.5hrs, however I think it is always good to  include these in the recovery drink/meal afterwards.

I also intend buying some empty capsules to fill with this elecrolyte mixture for use on long runs…

One important note is to also supplement magnesium. Our food is today grown in such organically depleted soils, that most of us are severly deficient in it. Recommend you take 400mg of elemental magnesium spread out over the day in a slow release form such as magnesium chelate (best).

Merry Xmas everyone, and a have fun filled, healthy year ahead!

Mike

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Fat Burning – using body fat instead of carbohydrates as fuel

In this article the fat burning processes are well explained and the latest scientific research dispels many popular myths. Mike

Fat oxidation through intense exercise

Fat burning is a very popular and often-used term among endurance athletes. But is it really important to burn fat – and, if so, how can it best be achieved? Asker Jeukendrup looks at the latest research

The term ‘fat burning’ refers to the ability to oxidise (or burn) fat, and thus to use fat – instead of carbohydrate – as a fuel. Fat burning is often associated with weight loss, decreases in body fat and increases in lean body mass, all of which can be advantageous for an athlete.

It is known that well-trained endurance athletes have an increased capacity to oxidise fatty acids. This enables them to use fat as a fuel when their carbohydrate stores become limited. In contrast, patients with obesity, insulin resistance and type II diabetes may have an impaired capacity to oxidise fat. As a result, fatty acids may be stored in their muscles and in other tissues. This accumulation of lipid and its metabolites in the muscle may interfere with the insulin-signalling cascade and cause insulin resistance. It is therefore important to understand the factors that regulate fat metabolism, and the ways to increase fat oxidation in patients and athletes.

Fat oxidation during exercise

Fats are stored mostly in (subcutaneous) adipose tissue, but we also have small stores in the muscle itself (intramuscular triglycerides). At the onset of exercise, neuronal (beta-adrenergic) stimulation will increase lipolysis (the breakdown of fats into fatty acids and glycerol) in adipose tissue and muscle. Catecholamines such as adrenaline and noradrenaline may also rise and contribute to the stimulation of lipolysis.

As soon as exercise begins, fatty acids are mobilised. Adipose tissue fatty acids have to be transported from the fat cell to the muscle, be transported across the muscle membrane and then be transported across the mitochondrial membrane for oxidation. The triglycerides stored in muscle undergo similar lipolysis and these fatty acids can be transported into the mitochondria as well. During exercise, a mixture of fatty acids derived from adipocytes and intramuscular stores is used. There is evidence that shows that trained individuals store more intramuscular fat and use this more as a source of energy during exercise (1).

Fat oxidation is regulated at various steps of this process. Lipolysis is affected by many factors but is mostly regulated by hormones (stimulated by catecholamines and inhibited by insulin). The transport of fatty acids is also dependent on blood supply to the adipose and muscle tissues, as well as the uptake of fatty acids into the muscle and into the mitochondria. By inhibiting mobilisation of fatty acids or the transport of these fatty acids, we can reduce fat metabolism. However, are there also ways in which we can stimulate these steps and promote fat metabolism?

Factors affecting fat oxidation

Exercise intensity – One of the most important factors that determines the rate of fat oxidation during exercise is the intensity. Although several studies have described the relationship between exercise intensity and fat oxidation, only recently was this relationship studied over a wide range of intensities(2). In absolute terms, carbohydrate oxidation increases proportionally with exercise intensity, whereas the rate of fat oxidation initially increases, but decreases again at higher exercise intensities (see figure 1). So, although it is often claimed that you have to exercise at low intensities to oxidise fat, this is not necessarily true.

In a series of recent studies, we have defined the exercise intensity at which maximal fat oxidation is observed, called ‘Fatmax’. In a group of trained individuals it was found that exercise at moderate intensity (62-63% of VO2max or 70-75% of HRmax) was the optimal intensity for fat oxidation, whereas it was around 50% of VO2max for less trained individuals (2,3).

However, the inter-individual variation is very large. A trained person may have his or her maximal fat oxidation at 70%VO2max or 45%VO2max, and the only way to really find out is to perform one of these Fatmax tests in the laboratory. However, in reality, the exact intensity at which fat oxidation peaks may not be that important, because within 5-10% of this intensity (or 10-15 beats per minute), fat oxidation will be similarly high, and only when the intensity is 20% or so higher will fat oxidation drop rapidly (see figure 1).

Figure 1

This exercise intensity (Fatmax) or ‘zone’ may have importance for weight-loss programmes, health-related exercise programmes, and endurance training. However, very little research has been done. Recently we used this intensity in a training study with obese individuals. Compared with interval training, their fat oxidation (and insulin sensitivity) improved more after four weeks steady-state exercise (three times per week) at an intensity that equaled their individual Fatmax (4).

Dietary effects – The other important factor is diet. A diet high in carbohydrate will suppress fat oxidation, and a diet low in carbohydrate will result in high fat oxidation rates. Ingesting carbohydrate in the hours before exercise will raise insulin and subsequently suppress fat oxidation by up to 35%(5) or thereabouts. This effect of insulin on fat oxidation may last as long as six to eight hours after a meal, and this means that the highest fat oxidation rates can be achieved after an overnight fast.

Endurance athletes have often used exercise without breakfast as a way to increase the fat-oxidative capacity of the muscle. Recently, a study was performed at the University of Leuven in Belgium, in which scientists investigated the effect of a six-week endurance training programme carried out for three days per week, each session lasting one to two hours(6). The participants trained in either the fasted or carbohydrate-fed state.

When training was conducted in the fasted state, the researchers observed a decrease in muscle glycogen use, while the activity of various proteins involved in fat metabolism was increased. However, fat oxidation during exercise was the same in the two groups. It is possible, though, that there are small but significant changes in fat metabolism after fasted training; but, in this study, changes in fat oxidation might have been masked by the fact that these subjects received carbohydrate during their experimental trials. It must also be noted that training after an overnight fast may reduce your exercise capacity and may therefore only be suitable for low- to moderate- intensity exercise sessions. The efficacy of such training for weight reduction is also not known.

Duration of exercise – It has long been established that oxidation becomes increasingly important as exercise progresses. During ultra-endurance exercise, fat oxidation can reach peaks of 1 gram per minute, although (as noted in Dietary effects)fat oxidation may be reduced if carbohydrate is ingested before or during exercise. In terms of weight loss, the duration of exercise may be one of the key factors as it is also the most effective way to increase energy expenditure.

Mode of exercise – The exercise modality also has an effect on fat oxidation. Fat oxidation has been shown to be higher for a given oxygen uptake during walking and running, compared with cycling(7). The reason for this is not known, but it has been suggested that it is related to the greater power output per muscle fibre in cycling compared to that in running.

Gender differences – Although some studies in the literature have found no gender differences in metabolism, the majority of studies now indicate higher rates of fat oxidation in women. In a study that compared 150 men and 150 women over a wide range of exercise intensities, it was shown that the women had higher rates of fat oxidation over the entire range of intensities, and that their fat oxidation peaked at a slightly higher intensity(8). The differences, however, are small and may not be of any physiological significance.

Nutrition supplements

There are many nutrition supplements on the market that claim to increase fat oxidation. These supplements include caffeine, carnitine, hydroxycitric acid (HCA), chromium, conjugated linoleic acid (CLA), guarana, citrus aurantium, Asian ginseng, cayenne pepper, coleus forskholii, glucomannan, green tea, psyllium and pyruvate. With few exceptions, there is little evidence that these supplements, which are marketed as fat burners, actually increase fat oxidation during exercise (see table 1).

Table 1

One of the few exceptions however may be green tea extracts. We recently found that green tea extracts increased fat oxidation during exercise by about 20%(4). The mechanisms of this are not well understood but it is likely that the active ingredient in green tea, called epigallocatechin gallate (EGCG – a powerful polyphenol with antioxidant properties) inhibits the enzyme catechol O-methyltransferase (COMT), which is responsible for the breakdown of noradrenaline. This in turn may result in higher concentrations of noradrenaline and stimulation of lipolysis, making more fatty acids available for oxidation.

Environment – Environmental conditions can also influence the type of fuel used. It is known that exercise in a hot environment will increase glycogen use and reduce fat oxidation, and something similar can be observed at high altitude. Similarly, when it is extremely cold, and especially when shivering, carbohydrate metabolism appears to be stimulated at the expense of fat metabolism.

Exercise training

At present, the only proven way to increase fat oxidation during exercise is to perform regular physical activity. Exercise training will up-regulate the enzymes of the fat oxidation pathways, increase mitochondrial mass, increase blood flow, etc., all of which will enable higher rates of fat oxidation.

Research has shown that as little as four weeks of regular exercise (three times per week for 30-60 minutes) can increase fat oxidation rates and cause favourable enzymatic changes(10). However, too little information is available to draw any conclusions about the optimal training programme to achieve these effects.

In one study we investigated maximal rates of fat oxidation in 300 subjects with varying fitness levels. In this study, we had obese and sedentary individuals, as well as professional cyclists (9). VO2max ranged from 20.9 to 82.4ml/kg/min. Interestingly, although there was a correlation between maximal fat oxidation and maximal oxygen uptake, at an individual level, fitness cannot be used to predict fat oxidation. What this means is that there are some obese individuals that have similar fat oxidation rates to professional cyclists (see figure 2)! The large inter-individual variation is related to factors such as diet and gender, but remains in large part unexplained.

Figure 4

Weight loss exercise programmes

Fat burning is often associated with weight loss, decreases in body fat and increases in lean body mass. However, it must be noted that such changes in body weight and body composition can only be achieved with a negative energy balance: you have to eat fewer calories than you expend, independent of the fuels you use! The optimal exercise type, intensity, and duration for weight loss are still unclear. Current recommendations are mostly focused on increasing energy expenditure and increasing exercise volumes. Finding the optimal intensity for fat oxidation might aid in losing weight (fat loss) and in weight maintenance, but evidence for this is currently lacking.

It is also important to realise that the amount of fat oxidised during exercise is only small. Fat oxidation rates are on average 0.5 grams per min at the optimal exercise intensity. So in order to oxidise 1kg of fat mass, more than 33 hours of exercise is required! Walking or running exercise around 50-65% of VO2max seems to be an optimal intensity to oxidise fat. The duration of exercise, however, plays a crucial role, with an increasing importance of fat oxidation with longer exercise. Of course, this also has the potential to increase daily energy expenditure. If exercise is the only intervention used, the main goal is usually to increase energy expenditure and reduce body fat. When combined with a diet programme, however, it is mainly used to counteract the decrease in fat oxidation often seen after weight loss (11).

Summary

Higher fat oxidation rates during exercise are generally reflective of good training status, whereas low fat oxidation rates might be related to obesity and insulin resistance. On average, fat oxidation peaks at moderate intensities of 50-65%VO2max, depending on the training status of the individuals(2,8), increases with increasing exercise duration, but is suppressed by carbohydrate intake. The vast majority of nutrition supplements do not have the desired effects. Currently, the only highly effective way to increase fat oxidation is through exercise training, although it is still unclear what the best training regimen is to get the largest improvements. Finally, it is important to note that there is a very large inter-individual variation in fat oxidation that is only partly explained by the factors mentioned above. This means that although the factors mentioned above can influence fat oxidation, they cannot predict fat oxidation rates in an individual.

Asker Jeukendrup is professor of exercise metabolism at the University of Birmingham. He has published more than 150 research papers and books on exercise metabolism and nutrition and is also consultant to many elite athletes

References
1. J Appl Physiol 60: 562-567, 1986
2. Int J Sports Med 24: 603-608, 2003
3. Int J Sports Med 26 Suppl 1: S28-37, 2005
4. Am J Clin Nutr 87: 778-784, 2008
5. J Sports Sci 21: 1017-1024, 2003
6. J Appl Physiol 104: 1045-1055, 2008
7. Metabolism 52: 747-752, 2003
8. J Appl Physiol 98: 160-167, 2005
9. Nutrition 20: 678-688, 2004
10. J Appl Physiol 56: 831-838, 1984
11. Int J Obes Relat Metab Disord 17 Suppl 3: S32-36; discussion S41-32, 1993

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Recovery – how the right nutrition can help prevent overtraining

Nutrition to prevent overtraining

More in the series on recovery and the prevention of overtraining which again emphasises the importance of having a good balanced nutrition programme. – Mike


Specific nutritional practices can prevent overtraining and accelerate exercise recovery

At a glance

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.

In simple terms, overtraining is the result of intense training stimuli (and other stressors) combined with inadequate recovery. If appropriate recovery is not provided during hard training, you experience a downward spiral in which continued heavy training creates diminishing returns, and performance levels continue to get worse. However, determining precisely when the ‘overtraining line’ is crossed is very difficult. This is because the symptoms of overtraining are highly individualised and varied – a laundry list of physical, psychological, immunological and biochemical symptoms.

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

Box

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).

Carbohydrate Intake

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

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): [in press]

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