VFC e carga de esforço em atletas de TKD

RELACIÓN ENTRE EL DOMINIO FRECUENCIAL DE LA VARIABILIDAD DEL RITMO CARDIACO Y LA CARGA DE ESFUERZO EN TAEKWONDISTAS CHILENOS DE ELITE


Luperfina del R. Cortés Escobar
Tomás Herrera Valenzuela
Felipe Soro Álvarez

RESUMEN
El objetivo de este estudio fue determinar si existe relación entre el dominio frecuencial de la Variabilidad del Ritmo Cardiaco (VRC) y la carga de esfuerzo percibida por taekwondistas chilenos de elite.
Se estudio a cinco sujetos pertenecientes a selección chilena de taekwondo durante una semana de entrenamiento, a quienes se les valoró la VRC a través de un monitor POLAR RS 810 y el programa informático Kubios HRV versión 2.0. Por otro lado, se registró la percepción del esfuerzo de los deportistas después de cada sesión de entrenamiento El análisis estadístico de los datos se realizó mediante el paquete estadístico GraphPad Prism 4.0.
Se encontró una correlación positiva (P<0 bandas="bandas" carga="carga" componentes="componentes" con="con" correlaci="correlaci" de="de" entre="entre" esfuerzo="esfuerzo" frecuenciales="frecuenciales" hf="hf" la="la" las="las" lf="lf" los="los" mientras="mientras" mostraron="mostraron" ms2="ms2" n.u.="n.u." n="n" negativa="negativa" p="p" para="para" percibida.="percibida." que="que" relaci="relaci" u.n.="u.n." una="una" valores="valores" versus="versus" vrc="vrc" y="y">Los resultados obtenidos indican que la VRC en el dominio frecuencial se muestra como herramienta útil para detectar determinados patrones de comportamiento cardiaco vinculados a la carga de esfuerzo. Por otro lado, se puede establecer que la percepción del esfuerzo en los sujetos de estudio es un indicador valido para la planificación de la carga de entrenamiento.

Mãos evoluídas para lutar

FIGHTING SHAPED HUMAN HANDS

1. Kathryn Knight

The human hand is a finely tuned piece of equipment that is capable of remarkable dexterity: creating art, performing music and manipulating tools. Yet David Carrier from the University of Utah, USA, suggests that the human hand may have also evolved its distinctive proportions for a less enlightened reason: for use as a weapon (p. 236).

Carrier recalls that the idea occurred to him during an impassioned discussion with fellow biomechanic Frank Fish about sperm whales. Explaining that he had published a paper suggesting that the whales might use their spermaceti organs as battering rams, Carrier says ‘Frank didn't buy the argument and at one point he raised his fist and said, “I can hit you in the face with this, but that is not what it evolved for.”’ A light went on in Carrier's head. Sure, the human hand evolved for dexterity, but he adds, ‘You could manipulate the proportions of a chimp hand in ways that would enhance manual dexterity, but they would not necessarily end up with the proportions that we have.’ Maybe there was more to Fish's challenge than met the eye.

According to Carrier and colleague Michael Morgan, modern chimpanzees have long palms and fingers with a short thumb, while the human palm and fingers are much shorter and the thumb longer and stronger. Carrier explains that this squat arrangement allows us to clench our hand into a fist when we fold the thumb across the fingertips; however, chimp fingers form an open doughnut shape when curled. Could the tightly packed human fist provide internal support – buttressing – to the digits to protect them from damage during combat? In addition, Carrier wondered whether curling the fingers into a fist could allow punching men to deliver a more powerful blow (increase the peak force of an impact) than slapping with the open hand. Carrier and Morgan decided to find out whether hands are more effective when balled into a fist or wielded in a slap.

‘Fortunately, Michael had a lot of experience with martial arts and he knew people who were willing to serve as subjects’, Carrier recalls. Asking the athletes to thump a punchbag with their hands in a range of shapes (from open-handed slaps to closed fists) using various delivery styles (over arm, sideways and head on), Morgan and Carrier measured the force of each impact. However, they were surprised to see that the punch did not deliver more force per blow. ‘In terms of the peak forces or the impulse, it did not matter whether the subjects were hitting with a clenched fist or open palm’, Carrier says.

Next the duo tested whether buttressing the hand by curling the fingers and thumb stiffens the structure. They asked the martial arts experts to roll their hands into variations of the fist shape – two with the thumb extended sideways – and then push the first joint of the index finger against a force transducer to measure the rigidity of the knuckle joint in the presence and absence of the buttressing thumb. Impressively, the knuckle joint was four times more rigid when supported by the thumb. And when the duo measured the amount of force that the athletes could deliver through the fist surface of the index and middle fingers, they found that the presence of the buttressing thumb doubled the delivered force by transmitting it to the wrist through the metacarpals (palm bones) of the thumb and the index finger.

So our short, square hands are perfectly proportioned to stiffen our fists for use as weapons and allow us – well, males predominantly – to deliver powerful punches without incurring injuries.

• © 2013.

References

1. 1. Morgan, M. H. and 
   2. Carrier, D. R.

    (2013). Protective buttressing of the human fist and the evolution of hominin hands. J. Exp. Biol. 216, 236-244.

http://jeb.biologists.org/content/216/2/236.full.pdf+html