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The Corner: Body Composition and Performance
By Alan Couzens
7/1/2009 |
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The right size engine for your chassis.
One of the most pervasive yet completely inaccurate beliefs among top AG triathletes is that ‘lighter is better’ when it comes to triathlon performance. While there are certain advantages to a low body weight, particularly on certain types of terrain, there is a fundamental limit to how low you should go that is intimately related to the size of your chassis.
Take a look at the following automotive example:
Top speed: 134 mph (214 km/h)
0-60 mph (0-96 km/h): 5.3 sec
Engine type: 426 Hemi 7.0L V8
Displacement: 426 ci (6,980 cc)
Transmission: 4-speed manual
Max power: 425 bhp (317 kW) @ 5,000 rpm
Max torque: 490 lb ft (664 Nm) @ 4,000 rpm
Weight: 3,990 lb (1,813 kg)
Economy: 9 mpg (3.18 km/I)
Top speed: 138 mph (221 km/h)
0-60 mph (0-96 km/h): 5.3 sec
Engine type: 1.8L, DOHC, 4-cyl., 16-valve
Displacement: 111.9 cu in (1834 cc)
Transmission: 4-speed manual
Max power: 140 hp @ 6300 rpm
Max torque: 126 lbs-ft (17.4 kg-m) @ 5000 rpm
Weight: 2,643 lb (1,199 kg)
Economy: 28 mpg (11.82 km/I)
Two cars with almost identical top speeds but significantly different engines. The huge Hemi 426 in the 1966 Dodge Charger (one of the most powerful production engines ever made) needs to produce 317,000 Watts to propel the almost 4000lb Charger at 130mph. On the flipside, it only takes 104,000W to propel the Acura. That’s right, with the lighter body weight and better aerodynamics, it takes about 1/3 of the power to generate the same speed. A compelling argument for losing some weight and modifying the body of your vehicle.
But let me pose a philosophical question: How much can we modify a Charger and still call it a Charger? Sure we could replace some of the bodywork with lighter fiberglass panels, we could make it more aerodynamic by adding spoilers (as an aside, it was not until they added front spoilers to the Charger that it was a competitive Nascar racer. Prior to that, the power it created was generating too much lift and making it take off the ground like an airplane!!), but fundamentally we are stuck with the chassis of the car, the skeleton and essential organs that make up the Charger. So, ultimately, the Charger will always require a bigger engine than the Acura to go the same speed.
You’re probably seeing by now where this metaphor is going. You, like the Charger are stuck with your ‘chassis’, your bone and organ mass that constitute ‘you’. We can modify the bodywork somewhat but there will be a fundamental minimal power that will be required to propel your chassis at a competitive speed. One of the greatest follys of physiological testing is that we typically express aerobic capacity relative to total body mass, with the assumption that if you reduce body mass, your VO2max in ml/kg will improve linearly. This is not true. Considering that it is largely muscle tissue that is responsible for O2 uptake, your optimal aerobic capacity in ml/kg will follow an inverted U pattern, where there is an optimal body composition that affords you the most oxygen absorbing muscle for your frame size.
So rather than asking the typical question of how light can I get while still staying healthy, a more apt question may be what sort of muscle will I require to propel my body at competitive race speeds?
Let me use myself as a case study:
AC Specs (From last DEXA scan and lab tests):
Top Speed (Run) 10.6mph (16.9km/h)
Height: 193cm
Weight: 81.1kg
Engine (VO2max): 4.5 L/min
Bodyfat: 9.7kg (12%)
Fat Free Mass 71.3kg (88%)
Muscle Mass 27.3kg (33%)
Chassis (Skeleton+Organ) Mass 44.1kg (54%)
Max Power 0.94 HP (0.701 Kw)
Max Torque 75lb-ft
Economy (Run @ 7:00 pace) 0.15 mpg (3.5 L/min=78%)
World Class Distance Runner Specs
Top Speed (Run) 19.2mph (30.7km/h)
Height: 172cm
Weight: 64kg
Engine (VO2max): 4.77 L/min
Bodyfat: 3.8kg (6%)
Fat Free Mass 60.2kg (94%)
Muscle Mass 25.2kg (42%)
Chassis (Skeleton+Organ) Mass 31.9kg (53%)
Max Power 1.43 HP (1.07 Kw)
Max Torque 127 lb-ft (172Nm)
Economy (Run @ 7:00 pace) 0.22 mpg (2.4 L/min=51%)
So, a world class distance runner has a ‘top end speed’ almost double that of my own, despite a similar engine size. How do they do this? With a smaller chassis and a bit of modified body work but the central difference is the proportion of engine weight to chassis weight. As skinny as they look, with their light body and streamlined chassis, world class distance runners are ~40% muscle!
While it is tempting to look at overall vehicle weight, remember that if you are fundamentally more ‘Charger’ than ‘Acura’ you will always require more engine power, more muscle, to achieve a comparative speed. In my own case, even after a bit of bodywork modification to lighten up my panels as much as possible, I would still require an engine upgrade to a 5.6L engine to stand a chance against an Acura in an (aerobic) drag race.
It should be noted that even with these custom engine modifications, just as in the Charger/Acura comparison, a larger car will always have inferior economy to a smaller car and is the reason we don’t tend to see 6’4”, 80kg distance runners. However, increase the economy of the unit by adding a bicycle on a flat road (or moving the Charger/Acura drag race to the top of a hill) and all of a sudden the economy gap narrows.
How do I upgrade my engine (without having a heart transplant)?
Some, maybe even most, exercise physiologists would suggest that getting a heart transplant from someone with a larger cardiac volume is the only way to improve your VO2max. But in reality, the picture is not clear enough to reach that definitive conclusion.
The pendulum has swung back and forth over the years as to what ultimately limits VO2max. Is it central capacity or peripheral (muscular) demand? Recently, studies that have found no increase in VO2 with arm+leg vs leg only exercise seemed to suggest that it was indeed the ability of the central cardiovascular system to deliver O2 to the working muscles that limited VO2max in large muscle exercise. However, these studies used individuals who were not ‘large muscle mass trained’.
Other studies have shown a distinct link between muscle mass and VO2. Perhaps the most compelling are the ageing studies which show a very close correlation between reductions in VO2max and muscle mass as individuals age. Additionally, in athletes who are large muscle mass trained (e.g. X-Country skiers), VO2max does increase when comparing arm+leg w/leg only exercise.
Recently, a group of scientists has suggested a concept of’ symmorphism’ between central and peripheral factors, i.e. ‘build it and they will come’. Based on my own experience and the research to date, in my mind, this makes the most intuitive sense.
So, until science proves otherwise, my suggestion would be to focus on building the biggest (still oxidative) fibers that you can in the hope that this will stimulate further cardiovascular adaptation to meet the new demand.
Upgrading your ‘panels’ and building the right sized engine for your chassis represent the bulk of your physiological improvement as an endurance athlete. Further improvement will come from upgrading your engine to a more economical fat/carb hybrid as I outlined in a previous blog (Big A challenges you to a Drag Race). However, this, like the development of the automotive equivalent is a multi-year process. As I also outline in that article, economy alone is insufficient if the engine is not powerful enough to achieve competitive race velocities.
So, again, Big A is challenging you to a drag race. Just let me install the Hemi first
Train Smart.
AC
Alan Couzens, MS (Sports Science), CSCS, PES, is a coach and exercise physiologist who helps athletes over at www.EnduranceCorner.com. He has a passion for performance and has been coaching endurance athletes since 1993.
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