how much to eat and crunches and how many endless hours of training will it take to win. why are you here every day? because i want to win. this is my life and this is what i do. like and i can honestly say, like this is who i am. you see it. this is what i do. >> reporter: marlen is a trainer in boxing. >> i've seen her come in and she's all like just pouring down with sweat and when she is training really hard, i'm like, marlen, you want to eat something? she is no, i can't, i can't. she makes me want to cry when she does is that. >> reporter: the family struggles to find the money for national tournaments. >> i've gone even far as here at work to say, hey, we, you know, we don't have the money to send her. even the girls here at work have said, you know, here's 20. here's 60. >> reporter: it all has to add up. the money, the training, even her lunch. marlen is a fly weight. she has to weigh in at 112 pounds at 5'3". >> i'm 21 and i already have like all of these injuries and i'm like always sore and always tired. i've been doing this since i was like 11, so i've been doing this for a really long time with intense workouts so i have to make sure i treat my body right. >> reporter: before boxing, she was the chubby younger sister of four and a trouble-maker. >> i always had the last word. >> reporter: mousy? >> yeah, very, very quick tongue. people would get frustrated. >> reporter: you were smart but mouthy? bad combination. then her parents got divorced. her siblings began to move out. boxing sustained her. >> probably if i didn't have boxing, it would have probably messed me up like mentally because, you know, i don't care what anybody says, to have all your family just like go off in one shot, it's hard to deal with. >> reporter: marlen ended up living with her father david. she dedicated her life to training. >> for the past three or four years, she's grown up and she didn't have a chance to go out and meet a boyfriend and go with the girls and dance and have a good time. she never have time for that. >> reporter: her coach, rudy silva, took a central role in her life. what is her greatest weakness? >> i mean, sometimes she goes after you so much that she'll stay a little high, but that's not even that -- that bad. >> reporter: sounds like you're saying you have no weak ns? >> oh, i have a lot. i hear them all the time. >> reporter: what is he saying are your weaknesses? >> like something every day i get. whatever is wrong that day ♪ i was like 16 or something, they presented me with the most promising mexican. >> reporter: she became a national champ at 16 and dreamed of the olympics but women couldn't box in the game, even though they compete in every other sport. >> this one is heavy. every single national tournament i've entered, i've won. >> reporter: she also became an academic star. >> i was like on the debate team. i was in the national honor society. i was president of my class. i was an all a.p. classes and i had like a 4 four six something. >> bam. >> reporter: then some exciting news. the olympics decide to add women's boxing for 2012. >> when i was like in elementary, like i was really into greek mythology and stuff like that. i always thought like the olympics games are and i wanted to go and it just ended up being boxing. >> reporter: marlen postpones college to pursue olympic dreams. >> just another day. >> boxing for me has always been my number one sport. i was born in mexico. my kids are mexican americans and making the olympic, that will be something any parent, i don't care who it is or what race they are, they going to feel what i'm feeling right now. and we don't know how to behave sometimes. >> marlen esparza! >> eight spots at the olympic trials as the national champion, she is offered the first. >> the olympics is a big goal. >> yeah, it's huge. i honestly truly feel if i go to the olympics and medal, that i could probably be totally happy for the rest of my life. yeah, like completely happy. >> reporter: marlen is on her way. when, suddenly, her competitors sue saying marlen should have to fight them first for one of the coveted spot. >> it's stressful. it's something that i've been working for my whole life, and then not only did this come out of nowhere, but then there's the pressure not that anybody puts direct pressure on me, but i know that people are expecting from me. >> reporter: usa boxing decides to schedule a box-off. >> one thing about boxing, anything can happen. i beat all of them fairly easy. the closest bout i ever has was against christina cruz. >> reporter: christina cruz, just one of the champion fighters marlen will have to face. what happens if you lose in colorado? >> i don't even know. that would be horrible. i'm sorry. i'm going to cry! because it's just so weird. i'm sorry. i haven't lost in like nine years. and that would just be like -- like the worst thing that could ever happen to me. and i don't deserve it either. i mean, i work really hard, so i'm okay, like i know that i've done what i'm supposed to do. ♪ at shell, we believe the world needs a broader mix of energies. that's why we're supplying natural gas to generate cleaner electricity... that has around 50% fewer co2 emissions than coal. and it's also why, with our partner in brazil, shell is producing ethanol - a biofuel made from renewable sugarcane. >>a minute, mom! let's broaden the world's energy mix. let's go. to your kids' wet skin. neutrogena® wet skin kids. ordinary sunblock drips and whitens. neutrogena® wet skin cuts through water. forms a broad spectrum barrier for full strength sun protection. wet skin. neutrogena®. the wife. hey, babe. got the jetta. i wiped the floor with the guy! not really. i would've been fine with 0% for 36 months, but i demanded 60. no...i didn't do that. it was like taking candy from a baby. you're a grown man. alright, see you at home. [ male announcer ] the volkswagen autobahn for all event. we good? we're good. [ male announcer ] at 0% apr for 60 months, no one needs to know how easy it was to get your new volkswagen. that's the power of german engineering. to get your new volkswagen. with two times the points onake lunch dining in restaurants,ch? you may find yourself asking why not, a lot. chase sapphire preferred. there's more to enjoy. these are sandra's "homemade" yummy, scrumptious bars. hmm? i just wanted you to eat more fiber. hewy, oatie, gooeyness... and fraudulence. i'm in deep, babe. you certainly are. [ male announcer ] ber one. ♪ marlen esparza trains in a gym that stretches along a lonel houston i-10 in houston. >> she was in alternative school and not doing well at all and behavior wise. >> reporter: she brought her brothers to box, but they hated it. marlen begged rudy to train her. >> he laughed at me. >> the first thing i told her, was, well, i don't train female fighters. she walked away. >> reporter: she kept coming back so he tested her against the boys. >> i actually tried for about two weeks to break her, to try to make her quit. i was pushing her so hard. left hand up. left hand up. >> i kind of in my head was thinking like, ha, ha, he thinks that i can't do it and i so can. >> in a few weeks, instead of trying to make her quit, i was making some of the guys quit! >> reporter: at first, boxing was more challenging than she let on. >> i remember getting beat up like every day for like the first three years i was boxing and i was like, what is going on? i'm trying really, really hard here. i'm doing everything i'm supposed to do. >> reporter: but eventually she started winning. did you know then you had a championship on your hands? >> yes. this girl is going to make it. she has the heart of a champion. >> reporter: to make a champion, rudy has taken charge of marlen's life. do you let her have a boyfriend? >> no. >> reporter: is she allowed to party on the weekends? >> no. >> reporter: is she allowed to take a few days off and not train when she is worn out? >> no. >> reporter: that's a lot of no's for a 21-year-old girl. i mean, she's a young woman. >> i remember when she was 18 years old. she went to prom. i was at her house with her dad waiting for her to come home from prom. >> reporter: you were at her house? >> yes. >> reporter: with her father? >> with her father. >> he's been worse on me and it's been more difficult to actually have him in my life than my dad. yeah. for sure. because my dad really laid back. and my life would have been actually a lot more stress-free like, yes! life! but with rudy, it's like, why is this happening to me? >> reporter: there's a reason rudy is so tough. he's a police officer at jefferson davis high school, not far from the neighborhood where he grew up. you must look at this kind of poverty and think about your own childhood? >> reporter: coming from seven brothers and sisters, including my mom and him, that's nine people in a one bedroom apartment and a neighborhood very similar to this. >> reporter: boxing kept rudy out of trouble. he won the local golden gloves four times. >> i was like really focused. so there was quite a few times where that's what made the decision of me not going out to a party or going out to the movies, or just going and hanging out. no, i need to be at home. if i want to win this fight. >> let's go, let's go, let's go! come on, man. you're going to be late. >> reporter: these days. >> did you see the student come up there? >> reporter: he faces off with the kids at jefferson davis. >> you need to get to class. late again? you got to wake up earlier than that. you tell me you were going to be doing better. >> reporter: can boxing help them? >> i mean, you're talking to a boxing coach so i'm going to say yes! >> reporter: he uses boxing to keep the students focused. >> we made ring magazine this year. >> reporter: oh, right. that's great. kind of a wall of fame here. >> yes, it is. whenever they get more involved in the boxing, it seems like they start doing so much better in school. i know it did that for even my own little boy. elbows in. elbows in. >> reporter: yeah, he's focused. >> oh, and you should see his grades! his grades, i mean, he's a straight a student. >> reporter: marlen could be rudy's biggest accomplishment. >> he is like 90% of the reason why i am where i am. >> reporter: what is the 10%? >> 10% is just the fact that i alt with it because a lot of people don't stay with him because of how hard he is. the longest i've ever seen anybody stay with him consecutively is like two or three years. >> reporter: do you think that number is right, that percentage? 90% you and 10% marlen? >> i would say like 94. >> reporter: 94% you? >> yes. >> he is conceited. >> reporter: wow. wow. now, rudy needs to prep her for an unexpected challenge. a fight in colorado that will decide who gets a first shot at the olympic trials. but there's another latino boxer working with the same goal in mind. christina cruz. what would the olympics mean? >> oh, it would mean the world to me. >> reporter: why? >> just because everything that i've sacrificed for it, even like my trainer, the sacrifices he made. it's not only for me, it's for my team. and, you know, i just wake up every day thinking about it and it's just constantly goes through my mind. >> reporter: christina is also aiming for colorado. gunning for marlen esparza's crown. >> this is a sport where someone has to lose. ♪ ♪ pop goes the world ♪ it goes something like this ♪ everybody here is a friend of mine ♪ ♪ everybody, tell me, have you heard? ♪ [ female announcer ] pop in a whole new kind of clean with new tide pods... a powerful three-in-one detergent that cleans, brightens, and fights stains. just one removes more stains than the 6 next leading pacs combined. pop in. stand out. for a golf getaway. double miles you can actually use... but mr. single miles can't join his friends because he's getting hit with blackouts. shame on you. now he's stuck in a miniature nightmare. oh, thank you. but, with the capital one venture card... you can fly any airline, any flight, any time. double miles you can actually use. what's in your wallet? alec jr? it was a gift. to your kids' wet skin. neutrogena® wet skin kids. ordinary sunblock drips and whitens. neutrogena® wet skin cuts through water. forms a broad spectrum barrier for full strength sun protection. wet skin. neutrogena®. [ with the azerbaijani we didwrestling team.riment ♪ can febreze air effects defeat the smelly air in their gym for good? [ man ] what can you smell? [ inhales deeply ] a lot of flowers. it's on the zingy side of floral. potpourri factory, maybe. you can take off your blindfolds now. oh my gosh. [ laughter ] [ male announcer ] success. victory over odors, for good, both here and in your home. febreze. breathe happy. i thought i was going to training camp and now i have to fight. >> reporter: there's a lot of stake at the box-off in colorado springs, home of the u.s. olympic team. >> i guess, to put it bluntly, i'm a little bit pissed at them at what i am having to do. that covers it. i'm angry. >> reporter: just eight female fly weights will go to the olympic trials. these boxers came ready to fight for marlen's spot. >> oh, so ready. >> chosen. tears. >> that's why we are here. because we're ready. >> reporter: many u.s. boxers are working class latinos and african-americans used to fighting for what they want like tyresha. >> if it wasn't for boxing, i wouldn't be here. both of my parents are on drugs when i was 16 and i broke a jaw and broke a nose and hit a nerve and had to do community boxing. >> rah me dah is from idaho. >> a lot of my friends back home are latino. they are already married with kids and stuff. never went to school after high school, and, me, you know, having boxing, it's, you know, coming on a better path. >> in the red corner, marlen esparza. >> reporter: marlen beats her first box-off opponent, alex love. >> there you go, girl. very good. >> like i felt like i was fighting a 12-year-old kid. >> reporter: but she's more worried about christina cruz. >> the girls that we have to worry about are the girls that are like here, that have been fighting and know the point system like christina cruz and that is why she wins. >> number one in new york. number one. all right? christina news, number one. >> reporter: christina is the puerto rican kitchen defeating marlen. she gets to fight in front of joe frazier at madison square garden. boxing has changed her life. >> way to go. watch that right. that a girl. >> reporter: her family is on her side now. her mother cheers at her fights. but christina's mother was in jail when christina was growing up. >> let's go! >> reporter: her father asked her maternal grandparents to help raise christina. they were boxing fans. >> yeah. yeah. >> reporter: my grandmother, he was -- >> my grandfather, he was very much a part of it. he never got to go to any of my fights but he always made sure i was, you know, like good and even just cooking right food for me and always asking me about my fights. >> reporter: your grandparents have died? >> yeah, both of them passed about two years ago. >> reporter: oh, it's upsetting. i didn't mean to make you cry. they made you who you are? a tough girl? who is going to win at the garden? ♪ there's a hero >> reporter: the night before the fight, christina seeks camaraderie. a fellow boxer sings "hero" to keep their spirits high. ♪ ♪ finally see the truth that a hero lies in you ♪ irks oh, my god! >> yeah. >> why are you crying? but rudy keeps marlen far away at a hotel. >> she is probably going to go eat some really good food and just relax and go over film with these boxers and get some strategy. >> reporter: u.s. olympic boxing coach gloria peek has come to the box-off to get a first look at the future olympic hopefuls. >> good luck, baby. okay, lady, good luck. >> reporter: after 33 years of coaching men, coach peek has her eyes on the top two women, esparza versus cruz. >> i think out of the 112, these are the two top girls. christina, her frame and her size and everything makes her perfect for international boxing. however, marlen has learned all of the tricks of the trade for boxing internationally, so, you know, clash of the titans. >> reporter: these two women are bracing for a fight. >> christina runs, runs, runs, 1-2, runs, runs, 1, 2, runs, 1-2, like the same thing. >> reporter: how about marlen? what kind of a boxer is she? >> she likes to come forward. she's a pressure fighter. she likes to stay on top of you. >> reporter: the day of the fight, christina is relaxed, getting wrapped and ready at the gym. marlen arrives quietly. >> christine cruz boxes as a hobby. i box as a lifestyle. >> we're in the same weight class and we both want the same thing. this is a sport. someone has to lose >> reporter: just as marlen predicted, christina runs. amateurs box with head gear and only score points with a clean hit to the face or chest. 4-1 christina. >> that's good, that's good. >> reporter: 7-5, christina. and the winner is? oh, you're good! hey, did you know that honey nut cheerios is... oh you too! ooh, hey america's favorite cereal is... honey nut cheerios ok then off to iceland! let's go! keep your hands up! hands up! come on! >> pa, pa, pa, pa! >> stop! >> good job. >> was that good? >> and the winner is christina cruz. >> marlen has lost. >> my first loss in nine years. >> anything bother you at all? >> nope. feel great. >> told you that would be a clash of the titans. and it was. >> christina will go compete for the first olympic trial spot at the pan american qualifier in venezuela. >> yeah, i'm very excited. going tonother country to fight. representing usa. >> it's very early in the process. do you understand? >> i don't really know. that's weird. like, i don't feel like i really lost. it's weird. >> it is her first loss in the united states in nine years. since she was 13 years old. >> i don't know. like, i feel kind of blank. i don't really know. >> reporter: if christina wins in venezuela, she takes the olympic trial spot usa boxing had reserved for their national champion, marlen. >> not that we're waiting for this to happen, but she still has to win the qualifier, because if she doesn't, it defaults to marlen, that spot. >> bye. >> reporter: marlen goes home to await the results with her family. >> for a few days, it was kind of, like, sad and, you know, she's not used to losing. she has the perfect record up till then. the kind of kid that gives their whole life to a sport, the next thing you know, you take a loss, it's devastating for a little bit. but then marlen is a person that she's so strong, all that is going to do to her, bring her back stronger. >> she had planned to start training for the olympic trials. now she needs to raise money to continue competing. >> good. >> david esparza is a supervisor at this manufacturing plant. he works seven days a week, 12 hours a day to fund marlen's dream. >> i've been doing this. >> reporter: paying for her boxing? >> paying for her boxing. >> reporter: what's the biggest expense? >> it's been since she started going to the nationals. setting myself up to bring her by myself with a separate room and airplane tickets and rental cars and food and all that. >> reporter: expense, expense, expense. >> expense, expense, expense. it's been costing me, like, $20,000 to $25,000 a year. >> reporter: these blue collar parents had white collar dreams for their four children. why was that important to you? >> want them to be, you know, that success that i wasn't. that's how i feel? >> which parent don't want a kid to succeed? i came from mexico when i was 18 years old. the thing that i have learned about this country is that if you don't have no money, you're not going -- you're not going to make it in this country. >> we're going to do it, okay? >> reporter