This morning, when faced with the decision of “Should I train? or not” I have several bits of kit that tell me different things. Being a grown-up I don’t listen to them slavishly but I DO take into account the information I am being presented with.
Here are some thoughts:
1. After yesterday’s session my Garmin 920XT told me that my recovery time was 72 hours…eesh Saturday ! Well, firstly, that only means how long to wait until the next HARD session (VO2). So I CAN still train today, just easily/aerobically.
2. The Garmin device also shows RECOVERY HEART RATE too immediately after yesterday’s session. You have to wait 2 minutes for it to be calculated before pressing ‘SAVE’. Also true on 910 and other models. That info is put in a FIT file and so the likes of sporttracks pick it up. Here it is
Well, to be honest, I don’t know what to do with that info :-) Maybe someone will let me know. It is surely VERY dependent on when you precisely STOP the session. So, I ignore this.
3. In sporttracks I import my data and prefer to use that rather than Garmin Connect (which is now pretty good – but wasn’t years ago). And then in Sporttracks I use the TRAININGLOAD plugin. I’ve used this for years and it is VERY useful. It shows me a very complex graph. I’ll just explain the pertinent parts that are circled below
The vertical red line is today.
The red graph reflects my tiredness from all that training. So I’ve been on a downwards cycle for the last few months BUT I’ve been ramping it up over the last few days. This shows my entire TRIATHLON tiredness (I can also view it by discipline should I so wish). So this would tell me that I’ve been more tired historically (cumulatively at the time). Might be a time for a little rest or maybe I could do a little more. Inconclusive.
As the green line approaches zero it shows less readiness to train. It’s currently at 2. (See the circled box at the bottom). This to me indicates that I can still train. It could be much lower.
4. I could trust my coach and do what s/he says I should do today and/or give him/her all this info. Personally I think you SHOULD do that. I’m not on a particular plan at present though. Free training !
5. Then I use a waking HRV test every day by BIOFORCE. Garmin or Sporttracks need to incororate this info in their product offerings. But they don’t. Roll-on Connect IQ apps. Here is what the excellent BIOFORCE shows. (Also consider Elite HRV and ithlete which have additional functionality)
I won’t go into this too much right now. But it says I’m good to train. Although I have had a chequered past over the last week or so. (Which agrees to the falling green line and rising red line in Sporttracks – as it should). The Garmin RECOVERY TIME of 72 hours also takes into account the hangover from recent hard training. I often use BIOFORCE as my guide for any particular day – based on this I would NORMALLY train.
6. I have also been looking at FIRSTBEAT ATHLETE quite a bit. It has a COACHING FEATURE that is inbuilt and tells you what sort of future training loads you should put yourself under. I understand it uses EPOC calculations and is based on HRV from my Garmin. FYI: Firstbeat produce some of the recovery calculations used by Garmin.
This is pretty clear. REST. But work hard tomorrow and VERY hard the next day. Kinda what I’d planned. Good.
Note IT plans the future NOT ME.
You can see from the graph that I have circled my current load. It’s well within the grey limits of acceptable training range based on my fitness and number of weekly training hours. And yes it knows I have been slacking :-) Christmas…c’mon give me a break !
FIRSTBEAT ATHLETE does not take into account my swimming load as I currently cannot easily get HRV HR data into ATHLETE. So it is missing a vital component of my training load. So I cannot trust it totally. Then again, it is saying REST based on my cycling and running – so swimming would make it more likely to say rest.
7. How do I intuitively FEEL ?
I feel a bit tired. I could quite easily go for a run. It would probably have to be a Z2. My bike legs for sure need a rest. I could quite easily feel like a rest as well.
8. Start a session anyway?
A great feature of the 920XT and, from memory, the 620 & Fenix2 is the message that pops up 12 or so minutes into a session telling you how your recovery is. Similar to the Bioforce waking HRV I imagine. However once you’ve already started a session you will most likely either finish it or tone it down a bit. So this is useful info. But training when it suggests otherwise might impact recovery benefits.
ANSWER: So what did I do? Well I had an evening swim. Well I’m going to. Relatively short session. I listened to all the above markers and made my call. If you train more than 5 days a week, say more than 6/7 hours a week then I think you need some tools long these lines if you want to get better a little more smartly. The reason being that we improve/adapt as we rest from exercise – not AS WE DO IT. So training more and more STOP the improvement. We need to rest. These tools help us decide WHEN to REST.
You will rarely need more than one day of complete rest. You will usually need two clear days between hard sessions (which can include activity).
There you go. You could just use that last paragraph/sentence to guide you. It’s a good rule of thumb.
What do you do?
You can see the above info on the Garmin website and in some versions of the product manuals.
I’m not sure about the cadence info from the above table. I’ve always read that the OPTIMUM cadence was about 185 spm. So if you go ABOVE that then it may not be better. Then again I recall once looking at Mo F on youtube and counting (non scientifically) that he had a much higher spm on the last lap. Draw your own conclusions!
Source Below : is some public data I took from Steve Way on Garmin Connect.
He’s obviously a very good AG runner and this data, from memory, was from a training run. Comparing what he did with the Garmin data table you can see that your Running Dynamics by themselves might not be the sole best indicator of how good you are. (ie he is REALLY good but his stats are not perfect. Personally Iwould rather be really good than have perfect form stats!!)
However if you get nice blue lined running dynamics set of graphs and your VO2max is 75 then I reckon you’re good to go!
Reblogged from an original By Coach Mike Arenberg
In the last issue, I wrote about three New Year’s Resolutions to make triathletes fitter and faster in 2008. For the run resolution it was simple: do more tempo runs. Many elite and international coaches will tell you that one big reason that the East Africans are so dominant in distance running is that they do a huge amount of tempo work.
Coach Joe I. Vigil, Ph.D., coach of Athens Olympic marathon medalist Deena Kastor and Meb Keflezighi wrote, “Volume runs, when combined with a regular diet of tempo runs, are the single most important workout for the development of the distance component.” Dr. Jack Daniels adds, “Tempo running is one of the most productive types of training that distance runners can do. Training at this pace helps runners avoid overtraining and yields more satisfying workouts and better consistency.”
The purpose of tempo runs is to stress lactate clearance, not to overstress it. Done properly, tempo runs will increase anaerobic threshold, the point at which lactic acid starts to accumulate in your muscles. Not so long ago, Vo2max was the physiological measure considered the best indicator of running potential. Vo2max is the maximum amount of oxygen that your body can process to produce energy. The ability to run at the highest possible percentage of a runner’s Vo2 for a longer time is the result of one thing–tempo work, and lots of it–over a long time.
All the speed work, weekly mileage and Vo2max workouts won’t mean as much as they will with the addition of regular, consistent tempo work. If you read about the Kenyans’ training, it revolves around tempo work. Recently, Vo2max has lost its standing as the best predictor of running performance. A new measure, vVo2, has come to the forefront as the best indicator of running performance. vVo2 stands for velocity at Vo2max, or how fast you’re running when you reach Vo2max. Thus, it factors in your running economy, in addition to your cardiovascular and muscular capacity.
How Does It Work?
Most runners have trained their bodies with lots of long, slow distance running to deliver oxygen, but they haven’t trained their bodies to use it. Tempo running does just that. During tempo runs, lactate and hydrogen ions are released into the muscle. The hydrogen ions make the muscle more acidic. The better trained you become, the higher you push the threshold at which this occurs. This means that your muscles become more efficient at dealing with these byproducts. The end result is a less acidic muscle, one that has a new, higher threshold.
What Is Tempo Work and How Do I Determine Tempo Pace?
Tempo pace is not a single pace, but rather a range of paces both faster and slower than a calculated target. There are anaerobic threshold runs and aerobic threshold runs, both very effective. In our summer running program we use both, each done once per week. Tempo runs can be single bouts, such as 20-50 minutes at a specified tempo, or they can be run in two or more segments or bouts. (Some marathon runners do tempo runs in excess of 60 minutes). For instance, 20 minutes of tempo running can be divided into two segments of 10 minutes at tempo pace with 1-2 minutes easy jogging between segments.
The most important thing is to have an accurate idea of what your tempo pace range should be. Determining this is easier than you think. First, you find your vVo2, and then you do a little math.
There are many ways to determine vVo2, but the simplest method is to run a 1-mile time trial. Your pace for this effort is your vVo2. Then do the math. Your threshold training pace is 85-87% of your speed for the mile, and your aerobic threshold pace is 75-80%. It’s important to note when calculating these ranges that it represents a percent of velocity, not percent of your mile time. For example, if you run the mile in 6:30, your threshold pace would be 6.5 minutes divided by 0.85-0.87, or 7:28-7:39 pace. Your aerobic threshold pace would be 8:07-8:40 pace.
Another method is to run a 6-minute time trial on a track. Then determine your vVo2 by using the following formula:
vVo2 = distance covered in meters/360.
For example, if you covered 1,500 meters in 6 minutes, your vVo2 would be 1,500/360 = 4.16 meters/second. To convert your meters/second to 400 pace, divide 400 by meters/second. In this example, 400/4.16 = 96 seconds. 96 seconds x 4 will give you a vVo2 mile time of 6:24. 85-87% of 6:24 is 7:21-7:31, which would be your threshold pace, and 75-80% is 8:00-8:32, which would be your aerobic threshold pace. You can also use a recent 5K to estimate vVo2. Simply subtract 20 seconds per mile from your 5K race pace to get a good approximation of your vVo2 velocity.
Tempo runs can also be done using heart rate as a guide. After determining your maximum heart rate (MHR), tempo runs can be done at 80-90% of MHR, with aerobic threshold runs at the lower end (80-85%) and anaerobic threshold runs at the upper end (85-90%).
Now to the fun part, designing a week’s training using your vVo2.
Devote a day to each threshold (anaerobic and aerobic) and keep enough easy days in between so you’re well rested. A general guideline is to start threshold runs with a 20-minute run. The best way to design any week of training is to start with the end in mind. What I mean by end is the weekend long run. (Long runs and recovery run pace can also be calculated by using 70-75% of your vVo2 pace.)
If you run your long run on Saturday, do your first tempo run on Tuesday. This gives you 2 days of easy running in between. Tuesday would be your threshold run day. Again, the 20-minute run doesn’t need to be run in a single bout. 4×5 minutes with 1 minute’s easy running, 2×10 minutes with 2 minute’s easy jogging. Wednesday would be a recovery run, and Thursday would be your aerobic threshold run. Since the pace of the aerobic threshold run is slower, this run can be longer in duration. The same rule applies in dividing it up into manageable segments.
As a coach, the hardest concepts to communicate are the ideas of progression and overload. When do I add minutes to the tempo runs? How do I decide when to do the threshold paces? Tempo runs can be done all year long. Be patient and allow your body time to adapt. The only way to answer the second question is to perform a new vVo2 test or mile time trial periodically–say, every couple of months.
Remember: always design your training with your goal in mind. If you’re focusing on a specific race–5K, 10K or marathon–decide where you want to be with your tempo runs in the weeks leading up to that event. Don’t try to do too much too soon. Training is like combining two paints to make a new color. Once you add too much of one paint, you have to start over. Developing a higher form of fitness comes as a result of training systematically at various paces both faster and slower than your target pace. Stress both aerobic threshold and anaerobic threshold and you’ll see the results.
Coach Michael Arenberg has an MBS in exercise physiology from the University of Colorado. He has been a competitive distance runner and triathlete for 37 years, completing 25 marathons and 11 Ironman triathlons, including 3 times qualifying for the Ironman World Championships. He has coached U.S. men’s and women’s Olympic Trial qualifiers in the marathon and two top-10 finishers in the U.S. Men’s Marathon Championships, as well as multiple Ironman World Championship qualifiers. Coach Arenberg is available for coaching and can be contacted at email@example.com If you have a training question for Coach Mike, send him an e-mail at firstname.lastname@example.org. While he is unable to personally respond to every question, answers will appear from time to time in upcoming issues of Missouri Runner & Triathlete
Awesome half in Weymouth and a little tricky to say the least.
The longer races remain far from my speciality and are definitely a Challenge :-)
I’d previously relied heavily on gels and found that I just couldn’t consume the volumes required. Much easier route today was with a lower number of gels but combined with bars and the like as well as electrolyes++ from OSMO Nutrition with their Active Hydration product. As (I think) I’ve said before here I find that I can consume quite a bit with the Active Hydration product and still feel thirsty so, unscientifically at least, it seems to keep me better hydrated. Oh well, doesn’t hurt at any rate !
Vaguely interesting 3 minute video from the GSK lab Jenson doesn’t beat Mr Brownlee…sorry for the spoiler !
Let’s talk “Monthly HRV Load”…
You’ve seen it in the box on the left, but you’ve been too caught up in what your daily HRV score is telling you about how to adjust your workouts to really care.
After all, you can’t go wrong with the simple “green means go, amber means slow” guidelines, right?
While it’s tempting to limit HRV data to its day-to-day utility, the real juicy information lies within the bigger picture:
Am I receiving enough training stimuli to achieve my goals (performance, body composition, or other)?
Am I continuing to see progress or am I at risk of plateauing?
Are my methods, intensity, or volume more than my body can sustain over time?
These are the kinds of questions that can be explored when looking at monthly HRV load.
Nothing But Green
A green monthly HRV load is indicative of a relatively low level of stress over the last 30 days, which can be good or bad, depending on your goals at the time.
If your primary goal is to improve your fitness and HRV, a low monthly load may mean that you are not providing with your body with a large enough stimulus to continue seeing improvements in your conditioning.
One of the biggest misconceptions about HRV is that if you’re training hard, you should expect to see a moderate or high load. The reality, however, is that if you’re been on the same program and aren’t seeing much improvement in the gym or in your training, chances are that the body has already adapted to the program and this will often result in a low HRV load.
Once the body adapts to a program, the body perceives it as a low level of stress, regardless of how hard you “feel” like you’re training.
What you feel and what the body perceives are often two different things.
When looking at Monthly HRV Load, this means that context is important.
Have you experienced improvements in your performance, body composition, or other goals?
If yes, then you shouldn’t worry about having a low Monthly Load.
After all, the purpose of HRV monitoring is not to train yourself until you see amber readiness scores.
The purpose is to monitor you training so that you see continual progress while avoiding injury and overtraining; so long as you’re seeing that progress, don’t worry.
However, if you have been experiencing plateaus and your progress has been stagnant, consider tweaking your training load to induce the changes you’re striving for.
More often than not, a MED Monthly HRV load is a sign that your overall program and lifestyle is the right mix of stress and recovery.
This will be reaffirmed with a positive change in Monthly Change, or how much your average HRV score has improved over the last 30 days.
So this means if you see an amber monthly HRV load, it’s probably a good sign.
You are likely providing your body with enough stimuli to promote positive changes in performance, body composition, etc.
The key to maneuvering this phase is to carefully monitor your HRV for signs of overreaching or plateauing.
Think of the amber monthly load as the fulcrum of a teeter totter:
You are currently balanced, providing yourself with enough stimuli to improve but not so much that you increase your risk of injury and disease.
However, with a slight increase or decrease in stress load you could easily tip the teeter totter to the right or left, into the regions of exhaustion or undertraining.
If you’re monthly HRV load is red, something needs to change quickly.
You’re placing a higher amount of stress on your body than it can recover from and you are at increased risk of injury and disease.
Does this always mean that your physical training is running you into the ground?
Since HRV looks at the impact of all stressors on your autonomic nervous system, several influences are likely at play at once.
Possible culprits could range from a lack of sleep, to a break-up, to increased work stress, to a change in diet…
Critically examine the components of your daily life to get to the root of the problem.
The Monthly HRV Load is an important gauge to understand how your body is adapting to your program and lifestyle as a whole. Most often, a MED Load is the right amount the majority of the time, though you always want to consider the context of your training and changes to performance/fitness over the last 30 days.
If you’re seeing LOW Monthly HRV Load and very little or no progress, it’s likely time to change your program and/or up the volume/intensity a bit.
A MED Monthly load, on the other hand, is generally a good the right balance between stress and recovery and is what you’ll want to see more often than not.
Seeing a HIGH Monthly Load, however, is cause for concern and you’ll want to review you current training program and lifestyle stress to see what may be causing it. Although it’s normal to see a HIGH HRV load on occasion, if this is sustained for very long, you’re at a high risk for overtraining and/or injuries.
I’m trying to help those who get Achilles (and maybe calf/soleus too) pains. Pains that sometimes you can run through and sometimes you can’t. Perhaps a pain that stops you training sufficiently to improve.
Firstly I’m not a physio and my ‘Achilles solution’ to all your 5k injury woes is based on my experience of ‘me’ and others I know who have had Achilles problems; sometimes chronic.
There could be some sort of unusual physical issue with you or perhaps you have torn your Achilles. I’m not trying to help you people. Sorry.
There are various places that you can get these pains. I’m not going to give you all the medical names for each of them. It could be your heel or various places on your tendon or on the soleus/calf muscle. That general ‘neck of the woods’.
RICE – Rest, Ice, Compression, Elevation. That is a good mantra. Indeed ice alone might be sufficient to control/manage your issues (eg heel bursa). Let’s say you don’t ice for a couple of days then what happens? Right the pain comes back VERY quickly. So RICE is NOT solving most of the Achilles problems. It is not addressing the cause. Fine for a one-off injury but it will not solve a chronic issue. Chronic means longstanding of over, say, 3 months.
So the ultimate cause of your woes lies elsewhere. It will be mostly in one of more of these 3 areas: sub-optimal technique; inadequate strength; lack of specific flexibility.
MANY physios will tell you, by default, to do some strength exercises. Normally involving stairs and “tip-toes”. You might strike lucky.
Technique: A LOT of force goes through that part of your body when running. It doesn’t take much to put that force in just the wrong place and BANG or SNAP. You know the rest. Running biomechanics are VERY complex think about these:
- Before you run, run upright on the spot lifting your knees. That is pretty much how it should be when you set off. If you bend forwards at your hips then more force is directed through your Achilles. (There should be a slight forward lean coming from the ankles, put that to one side for the time being and run upright)
- You land on your toes. Fine. But if you do your heel MUST touch down immediately afterwards. If you don’t do that try running flat footed (mid-foot sounds better).
- IF you have imbalances in how each of your legs move or if your knees crash together or one of your feet clicks to the side; then these are areas you need to correct.
- A running SHOP will do a gait analysis to tell you the best type of shoe. Most often they are not qualified or appropriate to analyse your detailed running technique. Your local running club will be better able to guide you or even a coach there help you.
Strength: IF all the running muscles are not strong enough then you will favour the muscles that are strongest. Especially as you fatigue more. You become imbalanced and the forces are directed in the wrong place. You get injured.
- It makes sense to do “tip-toe” exercises eccentric/concentric/whatever. These strengthen the muscles around the injured area. That may well help.
- You should also strengthen your glutes and your quads your hamstrings and your hip flexors and, while you are at it, you might as well roll out your ITB. So what I am saying here is that you don’t have a weekly Strength-Conditioning-Plan do you! Oh yes a bit of core work can’t hurt too !
- Don’t get me wrong. Strengthening X may apparently cure your Achilles. However it can just be masking the true cause. That true cause could be a lack of strength but technique will probably underly the true longterm solution as well as contributing to your lack of strength in a certain area.
But what is the point of strengthening some muscles if you don’t (technique) or can’t (flexibility) use them properly?
Flexibility: OK if you are a guy reading this then you probably aren’t as flexible as you could be (that’s probably the safest thing I‘ll write in this post!). If you are inflexible, think how hard your muscles are working to move themselves when they get towards the limits of your flexibility. All that wasted energy! That will tire you out and slow you down. So flexibility = speed gain. I only say that as it is more likely to make you actually do it to get faster! Inflexibility will also lead to incorrect or constrained muscle movements having a similar effect to a lack of strength in that the forces are ultimately directly in the wrong way.
- It will therefore come as no surprise that I tell you to stretch your hamstrings, hip flexors and so on.
- However you will need to work quite a lot on hip mobility. If you know someone who can twerk or does Zumba then you need to be able to do all that funky stuff (though please not in public). This will do other things like allow your stride to be much longer (and make you faster !!)
- You will also need to work on mid-foot and maybe also ankle flexibility. (For mid/fore-foot) You should be landing on the outside of your foot rolling onto the ball of your big toe and then pushing off to the outside again. If you don’t do that you you will be changing the motion of your knee and you may be getting injuries there too!! If you are not rolling onto the ball of your big toe you are not ‘toe-ing off’ properly and that will make you slower. You MIGHT not be able to correctly change this because of your mid-foot or hip flexibility.
Rollers, spikey balls and massage help too. They help manage the condition. They won’t solve it.
I reckon that all makes sense. I won’t solve the world’s Achilles problems in 1000 words but I might solve yours.
Questions ladies and gentlemen please.
Taken from tritalk.co.uk
“Caffeine is one of the few proven ergogenic aids- the current optimum dosage that is needed is 5-mg/kg in the 60-90 minutes pre race or heavy session- the dose response curve flattens out after this. Caffeine is rapidly absorbed from the gut and reaches peak plasma concentrations within 1 hour- the blood half life is 3-6 hours, so shorter races do not need “maintenance doses”
Dose response was done with cyclists given 5,9 and 13mg/kg caffeine and this was the trial that showed no improvement gains above 5mg/kg.
Caffeine has been shown to extend endurance in strenuous aerobic exercise and also improves muscular strength and endurance in prolonged exercise. This has been placebo control trialled. The benefits have been shown to persist up to 5 hours after the initial dose.
Caffeine also theoretically mobilises free fatty acids and increases fat catabolism and reduces carb oxidation, but one study did not demonstrate any increase in plasma FFAs
Studies also done on swimmers doing 1500m trials and showed that each 500m split improved with caffeine and total swim time improved on average by 1.9%, though I am not sure how statistically valid this is.
Running studies have taken ” time to fatigue” and caffeine gave significant duration increases.
Interestingly, one study subjectively demonstrated a reduction in perceived exertion for the same exercise.
Second surge energy gel has 100mg caffeine in it
High 5 Energy Source extreme has 180mg/ sachet
SIS gels have 50mg
High 5 gels have 30mg
If you are trying to lose weight through running then read this and ignore ALL the other nonsense that is out there.
The following is by Author: Andrew Hamilton BSc Hons MRSC ACSM (For High5 nutrition, they sell great sports nutrition products and the images below are from their site)
Quite apart from the aesthetics of a slim toned body, for most sportsmen and women, lower levels of body fat equate to better performance. Andrew Hamilton explains the nuts and bolts of fat burning and how you can manipulate your training to burn more fat…
INTRODUCTION TO FAT BURNING
Although increased fat burning has beneﬁcial implications for sport performance, many people who exercise regularly do so for general ﬁtness, health and aesthetic reasons rather than to increase fat burning per se. So if you wander into almost any gym and ask people why they train or what spurred them to begin training, it’s hardly surprising that weight loss comes right at the top of the list!
Any exercise programme that promotes increased fat burning therefore can help you to reach and maintain your target body weight more easily, bringing you all the associated health and kudos beneﬁts sooner rather than later. Together, these facts explain why there’s such an interest in fat burning and how to maximise it during exercise.
About Andrew Hamilton
is the commissioning editor of, and sports nutrition writer for, ‘Peak Performance’, the worldwide leading research publication for athletes and coaches. He is also commissioning editor of and contributor for ‘Sport Injury Bulletin’, providing the very latest sports injury advances into practical advice on prevention, treatment and rehabilitation.
Andrew also writes for a number of other publications, including ’Cycling Weekly’, ’220 Triathlon’, ’The British Journal of Cycle Coaching’, ’Athletics Weekly’, and ’Workout Magazine’.
Before we get into the nitty-gritty of maximising fat burning, it’s important to understand that the fundamental laws of chemistry and physics still apply (see box 1) and there’s absolutely no way of circumventing them. If you want to lose weight, you have to create a ‘negative energy balance’ in your body – ie expend more calories than you consume. However, by enhancing fat burning, you increase the proportion of your expended calories that will come from stored body fat. A second important fact that needs to be born in mind is that all of us, all of the time, are burning all three types of food calories (fat, carbohydrate and protein) to produce energy. The contribution from protein is minimal except when vigorous exercise is performed in the absence of carbohydrate (a subject we’ll discuss in part II of this article) so in actual fact, most of your energy is derived from carbohydrate and fat. It follows therefore that increasing the proportion of your expended energy from fat is associated with a reduced proportion from carbohydrate and vice-versa. You can think of it as a kind of seesaw effect. As the proportion of carbohydrate burning increases, fat burning decreases; as the proportion that you burn fat increases, the carbohydrate contribution decreases. A third fact that needs to be hammered home is that if maximising fat burning is desirable, aerobic type exercise (also known as endurance, cardiovascular or stamina training) such as jogging/running, cycling, swimming, rowing, skipping, X-country skiing etc should form the mainstay of any exercise programme. That’s because during aerobic type exercise, energy is provided by combining carbohydrate, fat and (to a small extent) protein calories with oxygen. The role of oxygen is especially important here because:
- There’s an unlimited supply in the air around you and even a lean body contains a very large amount of stored chemical energy in the form of body fat. Providing you don’t exercise so vigorously as to ‘run out of puff’ (ie oxygen), you can continue to exercise for long periods without fatiguing, which helps you burn a lot of calories in total;
- Unlike carbohydrate (the other main fuel for the body), fat needs an abundant supply of oxygen in order to be converted to energy. Provided your exercise intensity isn’t too severe (ie you have enough oxygen ﬂowing around your body), you can derive a large proportion of energy throughout this aerobic exercise from fat.
Very high-intensity exercise like sprinting or lifting weights (resistance training) uses different metabolic pathways to produce energy, most of which comes from carbohydrate burning. This is why it’s not an effective way to burn fat, although some resistance training can enhance a weight loss programme by helping to sustain or increase muscle mass (see later).
THE FUNDAMENTAL LAWS OF FAT BURNING
Body fat can be thought of as form of stored chemical energy. Each pound of body fat contains approximately 3500kcals of energy, so to lose a pound of body fat over any given time period, you have to burn 3500kcals more energy than is contained in the food and drink you consume. This can be achieved either by increasing your energy expenditure (ie by training/exercising more), or reducing your calorie intake (eg by following a calorie restricted diet), or, even better, by a combination of the two. Although there seems to be a small degree of genetic variability that makes the process of fat burning somewhat easier in some individuals than others, these fundamental laws of chemistry and physics (energy in versus energy expended) are immutable.However, while you can’t overcome the laws of thermodynamics, the good news is that by manipulating your exercise intensity/duration and food intake/timing, you can increase the proportion of your expended energy that is derived from fat burning, which (as we will see) can yield signiﬁcant beneﬁts.
One of the most powerful ways to manipulate the proportion of fat used to produce energy is to adjust the intensity of your exercise. The question that follows therefore is how hard should your aerobic training be to maximise fat burning? As we’ve hinted above, lower intensities favour fat burning but as the intensity increases, carbohydrate becomes more and more important until at very high intensities, almost all of the energy to fuel exercise comes from carbohydrate burning and none from fat-burning.
Figure 1 shows some actual data gathered from recreational cyclists. You can see that that as the exercise intensity (in watts) increases, the rate of fat burning increases, reaching a maximum of around 35 grams per hour at 180 watts. Above 180 watts, the amount of fat burned drops off rapidly so that by 300 watts, it’s contributing virtually nothing. Carbohydrate burning increases steadily too but at around 180 watts (just as fat burning drops off) it jumps dramatically so that by 300 watts, it’s contributing 100% of the energy for exercise.
DON’T RULE OUT HIGH INTENSITY EXERCISE!
You might think that exercising exactly at your Fatmax intensity is the best way to lose body fat but this may not necessarily be the case. There are a number of reasons for this:
Larger total calorie burn – suppose you exercise at 60% of your maximum heart rate (MHR) for an hour, burn 500 calories and 50% of those come from fat then you’ll have burnt 250 fat calories. But now suppose you exercise at 75% MHR for an hour and burn 700 calories (because you’re working harder). Even if only 33% of your energy comes from fat, you’ll still have burnt 230 fat calories but in total, you’ve also burnt an extra 200 calories from other fuels (mostly carbohydrate). This means that you’ll have an extra 200 calories to play with in terms of food intake and still stay the right side of the thermodynamic equation for the day (remember, you have to create a negative energy balance).
Increased fitness and fat burning – Training at a higher % of your MHR will progressively increase your aerobic ﬁtness; in very simple terms, as time goes by you’ll be able to train harder and burn more calories per hour for less perceived effort. Even more importantly, by increasing your oxygen processing capacity, your muscle cells will become more efﬁcient at using fat for energy, even at higher intensities. This explains why someone who is ﬁt ﬁnds it relatively easy to stay lean. For example, a ﬁt runner who can sustain 16kmh (10mph) can easily burn 1000kcals in an hour. If they can do that while working at say 75% of MHR, they’ll probably derive something in the region of 400-500kcals from fat. But suppose you’re only ever used to working at 60% MHR. This kind of intensity presents little challenge to the aerobic system, so there’ll be relatively little improvement in aerobic ﬁtness. With a total calorie burn of around 400-500 per hour and a maximum of around 50% from fat, it’s unlikely you would burn more than 200 fat calories in an hour. Of course, you could achieve the same fat calorie burn as our ﬁt runner by doubling the length of your workout, but quite apart from the boredom, most people simply don’t have time for 2-hour workouts, and you still wouldn’t be improving aerobic ﬁtness at these lower intensities.
Increased resting metabolic rate – as mentioned earlier, some resistance training can be a very useful adjunct to an aerobic training programme for fat loss. This is because very high intensity exercise such as resistance training increases muscle mass, which is a very desirable thing. Kilo for kilo, muscle mass is metabolically far more active than adipose (fat) tissue. Increasing your muscle mass with the addition of some resistance training means that the rate at which you burn up energy even while resting can be boosted signiﬁcantly, helping you to achieve your negative energy balance more easily. The best way to maximise lean muscle mass is to add one or two sessions of resistance training into your weekly aerobic exercise program. You don’t need to spend hours at the gym either; very signiﬁcant beneﬁts can be had by as little as two 30-minute resistance sessions per week. Sessions comprising of 10-12 exercises designed to work all the major muscle groups (one to two sets of 10-15 repetitions per exercise with enough weight set so that the repetitions can only just be completed) will produce good results in those who are not experienced resistance trainers.
Although several studies have looked at the relationship between exercise intensity and fat oxidation at a particular intensity, it was only recently that this relationship has been studied over a wide range of exercise intensities (2). In general terms, what happens is that carbohydrate oxidation increases proportionally with exercise intensity, whereas the rate of fat oxidation initially increases but decreases again at higher exercise intensities (see ﬁgure 2). The point at which fat burning reaches its peak is known as ‘Fatmax’ and the range of exercise intensities close to Fatmax is sometimes referred to as the ‘Fatzone’.
It’s often claimed that you have to exercise at low intensities to burn fat, but you can see from the graph this is not necessarily true. The right hand side of the grey Fatzone is quite vigorous but still close to Fatmax. Another important point to emphasise is that your ﬁtness level will have a big impact on the exercise intensity at which you reach Fatmax.
In a series of studies conducted by Professor Jeukendrup and his team of researchers at the University of Birmingham, it was found that for trained subjects, exercising at a moderate intensity (62-63% of VO2max or 70-75% of maximum heart rate [also known as HRmax]) was the optimal intensity for fat oxidation. However, for less trained individuals, Fatmax occurred at just 50% of VO2max(2,3). This is not surprising really as we know that regular aerobic training ‘teaches’ the body to burn fat more efﬁciently.
In reality, the exact intensity at which fat oxidation peaks is less important because within 5-10% of this intensity (or 10-15 beats per minute), fat oxidation will be similarly high (ie in the Fatzone), and only when the intensity becomes dramatically higher will fat oxidation will drop rapidly. Moreover, this intensity is usually identiﬁable because at this point, many people will perceive a signiﬁcant step up in their rate of exertion.
Taken as a whole, the evidence suggests that for maximum fat burning during exercise itself, you should exercise aerobically at the higher end of your Fatzone, which depending on your ﬁtness will be around 60-80% of your maximum heart rate (NB your maximum heart rate is roughly given as: 220 minus your age in years). As for duration and frequency of exercise sessions, the most important factor is your total energy expenditure over any given time period. So for example, six aerobic training sessions per week of 30 minutes’ duration at say, 70% MHR would be equivalent to three sessions of 60 minutes at the same % MHR (180 minutes in total). The goal is to increase your total volume so that you burn more fat calories (but see box ‘Safety ﬁrst!’).
However, there is evidence to suggest that fewer but longer sessions (ﬁtness permitting) may be advantageous to burn fat because we know that fat oxidation becomes an increasingly important fuel as the duration of exercise increases (4). So for example, in the example above, three sessions of 60 minutes may be preferable to six sessions of 30 minutes. Another beneﬁt of structuring sessions this way is that it allows longer periods of recovery in between each bout of exercise.
Another caveat worth adding is that the type of aerobic exercise undertaken may impact the amount of fat burning even when the exercise intensity is identical. For example, fat oxidation has been shown to be higher for a given oxygen uptake during walking and running compared with cycling (5). The reason for this is not well understood, but some researchers believe that it is related to the greater power output per muscle ﬁbre in cycling compared to running. Compared to running, the work done during cycling is concentrated in fewer muscle ﬁbres because fewer muscles in total are involved in the cycling action. For the same workload therefore, these ﬁbres have to contract more intensely and as we have seen, at high muscular intensities, carbohydrate burning becomes much more dominant.
Finally, and as previously mentioned, any fat burning programme should ideally include some resistance training for all the reasons given earlier.
When building up your total weekly volume, you need to ensure you do so only gradually to avoid the risk of injury or burnout. Unless you’re already an experienced trainer, it’s strongly recommended that you seek advice from a ﬁtness professional before putting together any programme. This will help ensure you derive maximum beneﬁts as safely and comfortably as possible.
For many people, lifestyle factors such as work and family dictate what time of day they will train! However, if you have a choice, some evidence suggests that the longer the period between your last meal and your exercise session, the greater the proportion of energy that will be derived from fat (6). The most obvious way to take advantage of this effect is to train ﬁrst thing in the morning before breakfast and indeed, research has shown that the total fat oxidised during exercise (and for two hours after exercise) is greatest when morning exercise is performed in the fasted state (ie before breakfast) (7).
It’s important to stress however that this approach becomes less appropriate for longer duration sessions (over one hour) where ‘training on empty’ could result in excessive fatigue as a result of low blood sugar and stored muscle carbohydrate (glycogen). A ﬁnal recommendation that follows from the studies above is that where fat burning is the number one goal (rather than performance), consuming a carbohydrate drink before or during training is not recommended because it reduces the proportion of energy derived from fat during subsequent exercise (8). More generally, your nutrition before, during and after exercise will play a powerful part in determining how much fat you’ll burn but that’s a whole different topic and one we’ll consider in part II of this series!
1. Data from Bradley J, University of Central Lancashire, 2002
2. Int J Sports Med 24: 603-608, 2003.
3. Int J Sports Med 26 Suppl 1: S28-37, 2005.
4. Obesity (Silver Spring). 2007 Sep;15(9):2256-62
5. Metabolism 52: 747-752, 2003
6. Int J Obes (Lond). 2005 Aug;29(8):966-74
7. Appl Physiol Nutr Metab. 2006 Oct;31(5):502-11
8. J Sports Sci. 2003 Dec;21(12):1017-24