The word ‘muscle’ is an integral part of our everyday parlance and yet very few are aware of its composition. Much of our articulation about muscles is visual which almost always conjures up an image of a body builder, made mythical by scores of gyms and fitness centres across the globe. Sudhir Raikar, content architect at http://thegenebox.com/ presents a primer on power and endurance.
Picture courtesy: www.crossfitchisholmtrail.com
Let’s begin with a simple explanation of muscle strength, power and endurance to put our muscles in perspective. Sportspersons use them synonymously in common parlance but actually they don’t mean the same thing and demand specific training regimes.
Muscle strength is your muscle capacity for sporting action at a given point of time, Power refers to the explosiveness of your sporting action, and Endurance means how long you can sustain your muscle power.
Coming back to the moot point, what exactly are our muscles made of?
Our bodies carry about 650 muscles, each made of countless extremely long and thin fibers. The strength of a muscle depends on the number of fibers it is composed of. Muscle fibers not only differ from individual to individual, they vary between muscles too. . One major one, possibly the most important, is the microscopic anatomy of the muscles. It’s interesting to see how genetics influence our muscle build up. Our DNA decides the distribution of muscle fiber types.
A closer look at Fitness Genes
Genes like ACE (endurance & sprinting) & ACT (sprinting) are two key fitness genes. They favour sport where explosive power is critical as well as those sports where peaks achieved in short bursts of action separate the winners from the losers, like for instance weight lifting, sprinting, trail running and cycling. ACE and ACT work by virtue of a process called vasoconstriction (which is opposed to vasodilatation) which constricts the blood vessels to supply blood to the working tissue thereby producing power that helps bursts of energy sustain for a shorter duration.
Besides ACE and ACT, we have genes like NOS3 (enhances nitrite oxide production that enables short burst sprinting and also promotes fatty acid mobilization) and ACTN 3 (aids sprinting) which boost power and endurance. So, in the ideal event of all four genes favouring an athlete, he/she would be able to scale winning heights in sports that demand both power and endurance.
A person with hybrid genes will have equal proportion of slow twitch and fast twitch muscle fibre. This helps, say a cyclist, sustain fast twitch at the very start of the race or while climbing uphill for a short duration which helps him take a substantial lead over other participants.
So what’s Type I and Type II?
These are mainly Type I (slow twitch, red in color) and Type II (fast twitch, white in color). Type II has five sub types: II A (responsible for explosive energy or power), II B, II C, II AB and II AC.
Slow twitch is suited for endurance-centric activities, slow in contraction but very fatigue resistant. Fast twitch guarantees power but fades out very easily. To make matters more interesting, there’s a subset of fast twitch fibers that mirror slow twitch characteristics but with less fatigue-resistance compared to the slow counterpart.
Power athletes look more bulky because of their red muscle tissue with more glycolytic fibre while endurance athletes from mid-distance sport, in comparison, have muscle with lower density. Natural sprinters have a larger capillary density for glycolysis for type II muscle fibre. (Capillary supplies blood to the working tissue.)
That’s precisely why power athletes develop muscles very fast while an endurance athlete will not derive equally spectacular results from muscle building. An endurance athlete on the other hand needs more efficient VO2 max such that more oxygen is supplied to the working tissue and energy is optimized for long distance sport. An endurance runner would use more of fatty acid oxidation but a power athlete needs glycolysis – efficient use of ATP and glycogen while saving fatty acid oxidation for much later use.
Genes hold the reins but...
Generally speaking, we are born with close to equal number of both types, but there are evolutionary differences that decide the exact ratio. It’s a foregone conclusion that people with more of one fiber type will excel in the sport linked to that type. This genetic diktat is quite influential and can’t be overlooked while designing a budding athlete’s career blueprint. That said, the role of training can’t be overemphasized. Physical activity itself influences muscle fiber development. Training for long distance running promotes development of slow twitch fibers and helps convert the ‘slow’ subset of fast twitch fibers into slow twitch-like fibers. On the other hand, power sport like weights make both subsets of fast twitch fibers bigger and stronger.
Genetics and Athletics can mix well
Any competitive sporting performance demands phenomenal power and endurance. Time and again, we have observed that sporting endeavours often have performers working beyond their threshold levels. Therefore, it’s important to have a fair idea of the genetics that influences sporting performance. This will avoid the disappointment of indulging in rigorous but unscientific training sessions that yield little results. In fact, genetic tests are God sent for professional athletes to scale new heights in field performance as they help them know their strengths and weaknesses – the latter, they can efficiently work around and the former, they can effectively capitalize on thereby making the most of the ‘base period’ and ‘build period’ of the tailored workout regimes.