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Cycling Training: can your pedalling technique make you a more efficient rider?

A very interesting article that sheds new light on what is considered correct cycle pedalling technique, and shakes up some well established dogmas giving us plenty of good food for thought… Mike

How to increase cycling efficiency to improve competition performance

Cycling Training Contents Box

You’d think that when it comes to technique, cycling is a delightfully simple sport. But over the years, a number of theories have been advanced about the best way for cyclists to pedal and maximise their pedalling efficiency. Joe Beer looks at the evidence and tries to separate fact from fiction.

From a clinical perspective, the bicycle holds the moving limbs of the lower body in a fixed arc; you have your foot in a rigid shoe, fixed to the pedal with a shoe cleat, which essentially attaches your foot to the end of a crank arm. When spinning the cranks (pedalling), this ‘closed circuit’ provides a fairly predetermined movement pattern, which allows for very little personal flair or style.

In effect, when studying the movement patterns during pedalling, all cyclists’ legs look fairly similar to one another, regardless of the level of exertion, the terrain, or whether the rider is in or out of the saddle. This is in marked contrast to the huge variations that can be seen in runners’ leg gait or freestyle swimmers’ arm movement patterns. The key question, therefore, is whether and how can you become better at pedalling?

Foot action

There are many ways that riders have attempted to improve cycling efficiency (the amount of power produced for a given level of oxygen consumption), most notably trying to pedal in a way that accentuates the upward lift of the foot, and varying the pitch of the ankle in various ways. The exact method, terminology and descriptions of this technique depend on whose interpretation you read. Suffice to say there is no evidence that these methods produce any significant improvements in efficiency over the normal, simple method of simply concentrating on the ‘press-down’ phase of each pedal revolution(1). The best riders push down harder than the slower riders and therefore go faster – it’s as simple as that!

Rule #1: push the pedals and don’t over-analyse any special foot action

Copying the pros

It’s hard to know whether pro riders are fit, good at pedalling efficiently or fit and good at pedalling efficiently! Few studies have properly tracked the career of elite cyclists so if there are any changes in economy over time, the data to support this notion are virtually non-existent.

However, there is a famous paper, on a certain Lance Armstrong, which suggests the measured gains in efficiency in his early years (see box 1) were due to changes to the muscle structure as a result of training and maturity(2). However, this data has been challenged by some researchers(3,4). They have suggested that the time periods examined don’t show year-on-year comparisons, that VO2max and body mass changes were more significant than riding economy and, most importantly, that fundamental problems in data collection make the data impossible to compare over a seven-year period. Granted, the data presented by Coyle(2) show improvements in Armstrong’s fitness; however, this improved efficiency may have been an indirect observation rather than the actual cause of his subsequent success.

Lance Armstrong's Fitness

Likewise, a study using 69 cyclists from recreational to world-class level suggests that there are not significant differences in cycling economy between such widely varying subjects(5). So rather than their superb pedalling efficiency, the key to being a top dog cycling pro may instead be the maximum power, aerobic fuel efficiency, tactical awareness and fatigue resistance.

Rule #2: your potential maximum riding economy is likely already innately fixed. However, lower body fat levels and bike weight, increased strength and power, better tactics and correct sports nutrition can all make you a much better rider.

Fitness first

A common assumption is that elite riders must share similar traits in order to get to the top. One of these assumptions is that elite riders must be efficient because they ride huge distances every year (circa 25,000-45,000km). However, this is debatable. Data from professional teams has shown that across a batch of 12 world class riders cycling at around 400 watts (around 5 watts per kilo of body weight) gross efficiency can vary from 20.9 to 28% – in other words average to super-human efficiency(7). This is a huge variation considering these riders had all shone at elite level and all ridden massive distances.

Interestingly, data presented by the Spanish team that did the research actually suggests that those with a lower maximum aerobic capacity (VO2max) can adapt and make up for such shortcomings with increased riding efficiency(7). Interestingly, this phenomenon (of modest VO2max but superior efficiency) has also been hinted at by some researchers from the field of running biomechanics.

Higher cadence?

Many people have examined Lance Armstrong’s riding ability and (mistakenly) deduced that for all riders, the best way to pedal well is to spin the cranks at 95-100rpm. However, lets make a couple of things crystal clear:

1. The higher cadences used by professional riders is because they are producing as much as 400-500 watts in time-trial efforts or climbs of 20 to 60 minutes;

2. Recovery from day-to-day ‘tour’ riding is easier with higher cadence riding, so riders chose this as a matter of energy conservation(8). So while Lance may ride a time trial at close on 100rpm, he is sustaining over 450 watts. Lesser mortals can probably only sustain around 250-350 watts, so cadence can be significantly lower – say around 75-85rpm. This is especially so when climbing where many cyclists can find improved efficiency (and ability to climb) at around 70rpm.

Macintosh and his co-workers have shown that optimal cadence for 100, 200, 300 and 400w cycling occurs at 57, 70, 86 and 99rpm respectively(9). This casts some doubt on the age-old advice that cyclists should aim for 95rpm because ‘that’s what the pros do’. Sadly though, we don’t all generate 400 watts in time trial and fast climb efforts! In fact, in a review of studies in this area, scientists concluded that ‘the choice of a relatively high cadence during cycling at low to moderate intensity is uneconomical and could compromise performance during prolonged cycling’(10).

Rule #3: choose a cadence that mirrors your power output; slower riding and warm ups should use a lower cadence while high-effort time trials should use a higher cadence. Unless you’re an elite rider, it’s unlikely you’ll benefit from using cadences exceeding around 85rpm

Five things NOT to do to increase efficiency!

  1. Focus on lots of turbo trainer drills – it’s unlikely to help efficiency. Instead use rollers for balance, coordination and a smoother pedal action;
  2. Place a lot of emphasis on high intensity intervals in spin classes – there’s no proof this helps. A fixed wheel bike on the road or lower intensity coordination spin-bike riding will likely be more productive;
  3. Buy independent ‘Powercranks’ (where left and right cranks can spin independently of each other) These have been tested and have shown no benefits(6);
  4. Significantly cut down on carbohydrates or restrict feeding on longer rides to force your body to adapt and become more efficient. This is just likely to cause illness and burnout;
  5. Do excessive high cadence (speed of pedal rotation) riding in an attempt to be able to spin at 110 or even 120rpm. Unless you can match this up to a 400-450 watt sustained efforts or greater you are just making yourself great at pressing down on air, not forcing the pedals downwards!

Four ways to get more efficient

  1. Ride rollers: these consist of a simple three-barrel device, which is becoming increasingly overlooked now widescreen training systems can be connected to an indoor trainer. However, efficient track cyclists, time trialists and cyclo-cross riders use rollers as part of their efficient riding programme. Short-term observations suggest the smooth pedal style that balancing on such an unforgiving surface gives can equate to 1-2% improvement in efficiency measures.
  2. Ride more: though we don’t have a direct mileage verses efficiency table to prove more miles means better efficiency, good riders do ride their bike several times per week. A minimum level of riding must be adhered to (like any skill). Varying the cadences used, the type of bike (fixed wheel, night riding, off-road mountain bike, etc) and developing handling all helps to eke out a more efficient rider/bike partnership.
  3. Use non-circular chain rings (like the Cervelo test team!). The variable circumference Q-Ring front chain rings can give improved pedal efficiency(11). By increasing the resistance on the down-stroke and easing up across the bottom and top of the pedal stroke, non-circular rings can make pedalling easier without having to think about a new pedalling style, especially when climbing.
  4. Vary cadence deliberately, from very low cadence hills (eg 50rpm in a big gear with smooth, controlled pressure) up to fast spinning brief eight-second sprints to ignite lots of muscle fibres. There’s more than one cadence sweet spot or one speed of riding. By keeping it varied, the nervous system, muscles and energy systems have to adapt.

References

1 Med Sci Sports Exerc 2007; 39(6):991-995.
2. J. Appl. Physiol 2005; 98:2191-2196
3. J. Appl. Physiol 2005; 99: 1630-1631
4. J Appl Physiol 2005; 99: 1628-1629
5. Int J Sports Med 2004; 25(5): 374-379
6. Int J Sports Physiol Perform. 2009; 4: 18-28
7. Med Sci Sports Exerc 2002; 34(12):2079-2084
8. Med Sci Sports Exerc 2001; 33(8): 1361-1366
9. Med Sci Sports Exerc 2000; 32(7): 1281-1287
10. Int J. Sp. Phys Perf 2009; 4: 3-17
11. J Physiol Anthropol. 2009; 28(6):261-7

Joe Beer is an endurance coach working with triathletes, duathletes, sportive riders and time-trialists through his company JBST.com. He is also the author of ‘Need to Know Triathlon’ (Harper Collins)

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Triathlon training – Why swimming, cycling and running is not enough

Strength TrainingThe triathlete’s winter “off season” is no doubt the best time to get down to some productive gym work so as to start the next season even stronger. This article sets out the rationale and a good programme… Mike

It’s time to tear up the ‘old school’ rulebook…

There’s a revolution going on in sports training – and you’re invited!

Triathlon may be the ultimate test of cardiovascular endurance, but triathletes who neglect musculoskeletal strength and flexibility will never fulfil their true potential

Triathlon is an endurance sport consisting of swimming, cycling and running over various distances. In most modern triathlons, these events are placed back-to-back in immediate sequence, and a competitor’s official time includes the time required to ‘transition’ between the individual legs of the race, including any time necessary for changing clothes and shoes.

While there are various race distances the three most common are Sprint, Olympic and Ironman. Take a look at the breakdown (see table 1 below) for each stage of the event and you can see that when it comes to the Ironman competitors, these are no normal athletes!

table 1

Shifting paradigms

For most triathletes, the benefits of strength training are outweighed by the fear of gaining too much bulk, loss of flexibility and diminished ‘feel’ of their sport. Unfortunately this thinking keeps many triathletes from participating in a properly designed strength and conditioning programme.

Many triathletes tend to have a traditional ‘endurance training’-based paradigm, centred on volume of training and time spent training for the actual event itself. It’s all about wearing a badge of honour for the number of hours spent running, cycling or swimming. Unfortunately this is a pretty flawed approach, not least because there is a mass of research showing that volume of training is one of the main culprits of overtraining and injury incidence(1,2)

By and large the triathlon community has overemphasised the benefits of endurance-based training and underestimated the benefits of strength training. Triathletes will spend hours completing endurance sessions in the hope that they can squeeze a little bit of extra performance from their cardiovascular system, but are reluctant to spend just a couple of hours a week in the gym.

One heart, two lungs, lots of muscles!

Part of the reason for the above is that many triathletes have forgotten about the huge potential that the musculoskeletal system has to offer to performance and pay scant regard to its training benefits. Let’s not forget that the only reason your cardiovascular system is involved in the first place is because of the demand from your muscular system; your muscles don’t move because of cardiovascular demand – the demand on the cardiovascular system is elevated because of muscular demand.

If the musculoskeletal system cannot handle the stress of thousands of repetitions (which is what happens when you are training for a triathlon) then you need to condition the musculoskeletal system first. In other words, you should programme your body based on the movements it’s going to perform – not based on the cardiovascular system, which is an upside down method of programming!

Strength training in the gym can make a real performance difference via a direct ‘transfer of training’ effect into the event (see PP256 for a full explanation of this training effect). Typically the triathletes that I’ve worked with have had so little structural integrity that a resistance training programme to target their muscular weaknesses and imbalances had to be our first approach.

The fact is that for many triathletes, moving the body is the biggest problem – not their ability to transport oxygen! I’m currently working with a number of triathletes who have seen the light and are now benefiting from a structured strength training programme. For years they’ve been focusing purely on improving their cardiovascular system but more often than not, they’ve broken down at some point during their season through illness or injury. Using a motoring analogy, they were trying to put a new engine in a beaten up old car with worn out chassis and suspension. A better approach is to set to work on improving the chassis and bodywork first and tinker with the engine later.

Setting the programme and shifting the mindset

Triathletes typically cite three main areas of concern when considering engaging in a strength programme:

1. Increased mass – fear of weight gain and subsequent drop in performance is a real worry. However, this is not a problem; a correctly balanced training programme will develop relative strength and power (ie improved power and strength to weight ratio) without significant increases in weight;

2. Lack of time – many triathletes are convinced they won’t have any extra time to fit strength training into their already busy schedule. This is flawed thinking! Many triathletes have lots of time to swim, cycle and run but won’t consider adding just a small proportion of strength training into their training schedule. The key is to make sure that your programme is time efficient – 30-45 minutes duration (maximum);

3. Increased risk of overtraining – triathletes are often (rightly) concerned about overtraining, so there is a very real concern that extra strength work may tip them over the edge. However, the key is to ensure that the strength training sessions are quality focused and don’t have too much volume in them. That said, the risk of overtraining is much more likely to arise from hours and hours in the pool or on the road than a couple of 40-minute gym workouts!

Having convinced the triathlete that we can help them, the key is to develop a programme that will have a positive impact on performance. I like to tackle programme design using the following continuum:

Flexibility    Stability    Strength

Flexibility

Flexibility, corrective stretching and dynamic movement preparation should play a major role in every triathlete’s programme. This is not to say that you need to adopt a ‘stretch everything’ mentality but you do need to recognise that the nature of the sport means you undoubtedly have to address some flexibility issues before you even think about working on developing strength.

Box 1 (above left) uses the example of the cycling portion of the event to demonstrate why you may want to prioritise the development of flexibility before moving on to strength.

Stability

If I had to choose just two core exercises that produce the biggest bang for the buck, it would be the plank and side holds. Research has shown that these two stabilisation exercises result in far more recruitment of the core musculature than more traditional exercises such as sit-ups etc.

The plank is a static exercise for strengthening the abdominals, back and shoulders:

1. Position yourself on your elbows and toes (elbows under your shoulders);

2. Keep your ankle, hips and shoulders in line;

3. Maintain your back, head and body in a neutral position – think about squeezing your glutes together, tightening your abdominal muscles and pushing your chest away from the floor);

4. This is a static position – so don’t move!

5. Hold for 30-60 seconds.

Side holds:

1. Start by lying on your side, legs straight, feet stacked on top of each other;

2. Support yourself on your elbow, keeping it in line below the shoulder, and place free hand on your hip;

3. Balance on sides of feet (feet are stacked) – squeeze your glutes and tighten up through your stomach;

4. Don’t allow your hips to drop toward the ground;

5. Again, this is a static position – so don’t move!

6. Hold for 30-60 seconds.

Strength training

Here we focus on what the Americans like to call ‘big bang for your buck exercises’! These exercises are multi-joint, multiple-muscle group and sometimes multi-planar exercises that recruit considerably more muscle mass than a single joint or machine variation. The box below provides explanations of some of the best training exercises for triathletes:

Split squat (you can perform this exercise with bodyweight or external loading such as dumbbells or a barbell):

1. Place barbell on your back or dumbbells in your hand, and take a long step out (the shin of the lead leg will determine the horizontal length of this step during the lowering – keep it fairly vertical);

2. Aim to keep the trunk vertical throughout the movement;

3. The bottom position should be one where the knee of the rear leg is almost touching the ground. The top position should be just short of the end of range;

4. This can be progressed into dynamic and walking lunges once the appropriate level of control, stability and general strength has been achieved.

Single-leg hip extension (a great exercise to activate the gluteal muscles; most triathletes have problems activating their glutes as a result of spending so much time in the saddle):

1. Lying supine on the floor, bend your left leg to 90 degrees and straighten your right leg (make sure your toes are pulled up to your shin on both legs);

2. Your arms should be face up at 45 degrees from your body;

3. Now lift your entire body up one inch by pushing off your left foot. This is the start position;

4. Continue to lift your body ensuring you maintain a straight line and your thighs are parallel to each other (the only other parts of your body that are in contact with the floor are your arm, upper back and left foot);

5. Lower to one inch off the floor, pause and repeat for the desired repetition – be sure to keep your hips in a straight line.

Press-ups

A simple but extremely effective exercise for triathletes, press-ups are not just a great upper-body exercise, but a great exercise for the core (female triathletes note; if you struggle to complete a press-up it may have very little to do with upper-body strength and more to do with your core strength – make sure you build planks and side holds into your training). I’m not going to explain how to do a press-up here – you should all know how by now!

1. If you can’t do full press-ups, you can start on an incline;

2. If they are too easy simply slow the tempo (see PP 256 for an explanation of tempo), or try decline, medicine ball or weighted vest variations.

Inverse pulls

Second only to press-ups, this is possibly the most feared exercise in our training facility. Again this is a horizontal pulling movement that is a total body exercise and which really works the core.

1. Lie on your back under an Olympic bar that is placed in a squat rack just slightly beyond arm’s length;
2. Grip the bar with an overhand grip and pull the upper body to the bar so that the chest touches the bar;

3. Keep the body completely flat throughout the entire movement;

4. Once the exercise becomes easy (this will take some time!) you can increase the difficulty by raising the feet. If it is too hard to start with the legs bent.

Summary

Training the cardiovascular system alone and neglecting the musculoskeletal system and its contribution to performance is a big mistake that will inevitably lead to reduced performance. This article has hopefully provided an insight into how a strength and conditioning programme can help improve a triathlete’s performance by addressing not just the strength, but the flexibility and stability requirements too.

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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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