Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126803
a ll dea th s. Th at 's a IO la l o f m or e th an 1\\"0 OUI of e\'ery threr people, Diet a nd e xercise he lp pre-ven t art herosc1 erosis. :\ " ,th ibk d iel red uces fat in ta ke; exercise help s b Uill [at . Exercise a h a stim ul a tes bloo d flow a nd helps hl ood vessel s' elastici I v, 'T h ert' is some ind ica tio n th at vigo rous exe rci se ra ises th e H DL level. St udies al so suggest that a lo w fat di et reduces LDL. The heart The heart, the body's most important muscle, is two pumps. The left he art receives blood from th e lu ngs and pumps it into the aorta artery for delivery by the artery syst em. The right half of the hea rt pumps blood received fro th e vena cav a vei n m (carrying oxygen-poor blood ) to th e lu ngs for re-oxygenation. o T he hea rt is a bo u t as la rge as a fist . o The hea rt wei ghs a bo u t eigh t 10 I I o unces. o The heart's mech anical efficiency is a bo u t fif ty pe rcent , tw ice that of leg or arm muscles. o T he hea rt pumps th e four to six quarts o f blood in th e h uma n body th ro ug h 60,000 mi les of blood vessels. o The average resting heart rate is about 72 beats per minute. That's about 100,000 beats a day or close 10 40 million beats per year. o Th e difference between two hearts with resti ng pulse rates of 50 and 75 is about . 13 million beats per year. o H ea rt muscle works about twice as hard as the leg muscles of a runner. o The pressure involved in contracting the heart is abou t the same as squeezing a tennis ball. Benefits of a conditioned heart o It becomes larger and stronger . wi th exercise. o It beats fewer times pe r m inute. o It can deliver more blood with eac h beat, o It supplies bl ood and ox yge n to th e muscle s wi th less effort. o It del ivers more bl ood and oxygen d ur ing stress pe riods. ~ o Its i nc reased fitness ac ts as a go vernor which prevents excessive stimu la tion by adrena li ne in srress sit uations . Cardiac output Cardiac output, the volume of blood p umped through th e heart in a g ive n time period, is the product of: o Stroke volume. o H ea rt ra te. Mu ltiplying the volume of a sin g le stroke by th e stro kes per minute gives the volume of blood pumped in one minute. (T h is averages a bo u t five quarts in a n individual a t rest .) Initiall y, an increase in th e body's ox yg en dem and is sa tisfied with deeper breathing . Then ca rd iac o u tput tak es over: ( I )Stroke volume increases as effort intensifies. (2) Stroke volume tends to level off at abo u t 40 pe rce nt of m aximum ox ygen uptake. (3) H eart rat e. respon di ng to spe.cific oxygen dem ands, co n tin u es to in crease ca rd iac o u tp u t as ne cessary . Ca rd iac o u tp u t ma y in crea se as much as 15 times its rest level during intense exe rti o n as blood speed a p proaches 40 miles per hour. H eart rates vary in ind ividuals, bot h a t rest and during exertion. T he heart rate (or pulse) may be tak en by a p p lying pressure to a n art ery with a fin ger tip and co unt in g for 10 seconds, then multiplying by six to det ermine th e rate per minute. Two artery locations are popu lar for taking th e pulse: o The radial artery - loca ted in th e wrist. just be low the bas e of the th umb. o Th e caroti d artery - locat ed in th e neck, besid e the lary nx (Ada m 's apple ). H eart ra te level s rnav be a ffected bv co ndi tio ni ng , bu t th e max im um rat~ is gene tic. nature 's red li ne. This m axi m um decli nes grad ua ll y w ith aging. Maximum heart rate mav be es ti m at ed with th e foll owing 'form u la : 220 m inu s age. For exa m p le, a 20-year-o ld shou ld have a sa fe, pred icted max imum rat e of abo u t 200 beats per minute. This ca n vary a s much a s 20 beats either wa y. (In 1979, at age 26, Bra d Lackey had a measured maximum heart ra te of 214, a bo u t 20 beats higherthan hi s formu la-predicted m aximum.) Training won 't increase th e max imum heart rate, but it will in crease th e a bi li ty of th e hea rt to work at or near the maximum longer. Stroke volume may be in creas ed by trai ning. A greater stroke volume a llows th e heart to bea t slower w hi le delivering a given volume of blood. _ (Th is explains the lower res ting p u lse. rat es of end u rance a thletes. For example, a hea rt with twice the stroke vol ume capaci ty of a nother n eed beat o nly half as ma n y times to deli ver th e . same vo lume of blood.) ATVlIell1$ R ~ ~ TM '. " ~ ~ Covers it al/! ~ All that's happening in the world of allterrain vehicles. Every month. ·A II for only $5 a year. A TV News, America's A 11- Terrain Vehicle Newspeper. - Subscribe today! Adrenaline and the hormone system Adrenaline (also referred to a s epinep hrin ) is the body's stress hormone. A chemical supercharger. It helps th e body prepare for fight-or-night by increa sing the meta bolic rate of skeletal muscles. Adrenaline is found in th e adrenal glands which are located above th e kidneys. Research indicates (but ha s not ver ified) that increases in adrenalin e secretions in the blood are triggered by nerve reflexes in the cardiovascular system. Several things happen when adrena line enters the blood stream: o The heart bea ts faster . o Heart co ntractions become more fo rcef ul to increase st roke volume. o Blood vessels d ila te (expand) to a llow more bl ood flow. o Blood pressure goes u p . o Mental ale r tness i ncreases (as nerve cells beco me more excited). o The blood sugar level is increased as the conversion o f glycogen to glucose is acce lerated. o Intestina l activity is reduced to permit more b lood 10 reach th e working muscles. Th e end -resuh is an increa se in blood vo lume 10 th e skeleta l muscl es whi ch mav be as much as six times grea ter th an th at o f a body a t rest. The cardiovascular circulatory system The left side o f th e heart p u m p s o xygena ted blood fro m th e lungs in to th e aorta a rterv wh ich deli vers it into th e a rter y system for circu la tio n th rough out th e en ti re bod y. T h e o xygen-deplet ed blood is bro ught ba ck to th e rig h t side o f th e heart by th e ven ous (vein) syste m a nd pumped to the lungs to exc hange i ts ca rbo n dioxide for more ox yge n before returnin g to th e left side of th e heart 10 begin its next circui t. • Championsh ip T , ainin g ,by Dean M iller and L en W l'ed , inclu des Brad La ck ey's com p lete year-rou nd train in g program as well as in -depth fitness and tra in in g in fo rmation fo r all spo rts: 112 pages. ove r 80 p hotos and illustration s. T o orde r, send $9.95 p lus $1.50 postage an d handlin g to Cl ean sh eet Enterp rises, P.O . Box 241C . Tarzana, CA 91356 . Calijornia residen ts add 65( sales tax . . . - AMERICA'S MONTHLY AU-TERRAIN VEHICLE NEWSPAPER ~.~ ~.~. - o YES! Send me one full year (12 Issues) of ATV NEWS for only $5.oo! o I want to SAVE MORE!Send me two years (24 Issues) of ATV NEWS for only $9.00 $15.00 off the newsstand price! 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