1. Pick a race. Check out the calendars of races on the internet and set your goal for that first race.
2. Make sure you have all of the required equipment. Most of the "Mandatory Gear" is safety equipment. You can often borrow or rent some of it (even expensive mountain bikes). Know how to use all of the safety equipment.
3. Start doing "Brick" workouts. Bricks are training sessions that involve two activities (running/biking, biking/paddling, paddling/running). Your muscles and mind get into a groove while doing just one activity. Bricks help you increase stamina and shorten your transition times between activities.
4. Learn your nutrition requirements. Adventure racing burns huge amounts of calories and will deplete you of electrolytes more than any other endurance sport. In order to do well in a race that is greater than 4 hours you will need to be eating from the very beginning. There are different foods, gels, bars, and tablets that can keep you at peak levels of energy and nutrition even on expedition-length races.
5. Learn to navigate. Many races give the locations of the checkpoints using topographical coordinates. The team must determine the direction from checkpoint to checkpoint using a map and compass. Proper navigation will prevent your 100 mile race from becoming a 250 mile race. Besides your team will hate you if you get them lost.
6. Find a Team. Many first-time racers talk, beg, or bribe their friends or relatives into competing in their first race. That's okay so long as the relationship will survive the stress of competition. Even teams whose only goal is to have fun will feel the excitement of being in a race. Everyone on the team must have the same goals (just finish, top ten, win).
7. Join a club. There are more and more adventure racing clubs that conduct training clinics and workouts. Learning from others is the fastest way to get better at anything, especially adventure racing. You'll meet other racers who may be looking for a teammate for a race or who may be able to support you in an upcoming race.
8. Get the best instruction that you can for technical skills. When choosing an instructor, look for one with the highest level of experience. Any "dope with rope" can show you how to rappel or ascend. There are also proven techniques to deal with emergencies while on rope. Learn them too.
9. Communicate and work as a team. Just because you're the team captain doesn't mean that the other team members don't have ideas to help the team. Ask for input and value their suggestions. Many triathletes have a struggle when competing in an adventure race. They often mentally compete with their own teammates. They'll speed to the top of a long hill, leaving their team behind. The team should redistribute some of the team gear or use a tow system to make the whole team faster.
10. Respect the Environment. Pay attention to trail designations and private property boundaries. Participate in trail maintenance projects and park clean-ups. Make a workout out of moving loads of soil to remote sections of trails. That way groups and events will be invited back in the future.
Not all "sprint" races are created equal. But largely speaking you can expect to paddle a boat, ride a bike and do some trail running together with a teammate or teammates. You'll probably receive a map with checkpoints already plotted on it. And in some cases you may have some special tests either integrated into the race or as a field breaker at the start. Some examples of a special test might be climbing a cargo net or running to the top of a hill near the start line to retrieve the team passport/punch card
Not every race is created the same but it's safe to say that most race promoters will tell you what gear you must bring in order to compete. They won't necessarily tell you what else you might find useful to improve your team performance. That's where you can:
a.) Have experience or
b.) Read the rest of this
#1: Know how to read a map and how to use a compass. You may be able to run all day and bike all night. But if you don't know where you are going none of that will matter much. At most sprint races you won't be overwhelmed by the navigational difficulty. Much of the navigation will involve following trails that are marked on the map to easily identified features where the controls will be placed. Examples of those features might be: trail intersections, stream crossings, lakes or hilltops. There might be a little off-trail navigation but for the most part if you can use a road map you'll probably be able to figure out the navigation. When there is off-trail navigation it will most likely involve reaching an attack point that is on trail and then following a bearing or perhaps a feature like a stream a short distance to some other feature that can be identified on the map.
Want some practice? Go to an orienteering event (DVOA runs events in southern NJ, Eastern PA and Delaware), get some basic instruction and then try a yellow course to get the basics of map reading. Once you're comfortable with Yellow (which may well be the first time through) step up and try an Orange course. This will get you a little off-trail.
#2: Minimize the weight that you carry. If you carry something it should be worth carrying. Not carrying mandatory gear can get you disqualified. Therefore it is worth carrying. If you believe otherwise please send a check for $200 and I'll happily kick you out of the next race I direct. Doesn't sound very rewarding, does it? ;)
Everything else you cannot carry is fair game. For example: many sprint races feature some sort of a central transition area. In a sprint race that estimates 4-6 hours of competition and has two or three transitions that means you might reasonably expect to pass through every one to two hours. Provided, of course, you've followed my first piece of advice and know where you are going. Carry one energy bar, or a brownie or a bag of chips in your pack and eat it if you need it. Leave most of your food in the transition area and plan on eating each time you pass through transition. Same goes with liquid. Start with a full camelback and go train for an hour or two. Stop and check how much you drank. I'm going to guess that it will be something less than a full 100oz bladder. You can trim a few pounds of weight carried if you dial in the right amount to carry. Again, be sure to refill in transition and also have a bottle of water or sports drink in the TA that you can consume with your snack and leave behind. The more proficient you get the more you'll be able to shave this weight down. There are tons of other items that you can shave weight with and still not put major risk on completing the event. For example: patches weigh less than tubes (although having at least one tube can be worth it even if not mandatory).
#3: Know how to use your bike repair stuff. Ever see an auto racing event? Changing a tire isn't a one person affair. Somebody runs the jack, somebody removes the lugnut(s), somebody removes the wheel and somebody mounts the replacement wheel. It's precison teamwork. You can be much the same way with your bikes. Somebody should be getting the wheel off the bike while somebody is grabbing tools to remove the tire. While the tire is coming off the rim someone should be partially inflating the replacement tube, etc.... You can add ten minutes to your race time by thinking of a flat repair as racing. Same thing with a chain break tool. It can happen, so know how to repair a broken chain and be able to have multiple hands in the project.
#4: Is it a three person team? Are you using canoes for the paddle leg? If the answer is yes to both of those questions then bring something for the person in the middle of the boat to sit on. Some canoes have a built in middle seat but that is the exception rather than the rule. One easy soltion is to bring a milk crate and something to tie it to the center yoke with. If you don't provide some means for the third person to sit up they will probably have a devil of a time producing any kind of paddle power. Yes, they could kneel for the entire paddle leg. But if you think that's the best idea then be willing to be the person that kneels in the middle of the boat on the rocks and sand that are inevitably in the bottom of the boat. Be willing to explain to significant others and riding buddies how you developed abrasions on your knees while out "racing". :) Anyhow, if you don't have some sort of solution to get that middle paddler up, you'll end up with one teammate effectively being dead weight.
I could go on all day but those are my big tips based on the things that I've seen while racing. These are the big ticket items that clearly separate novice from experienced teams. And these are no cost/low cost items that will most likely make a much larger improvement in your performance than that new carbon fiber mountain bike you've been lusting to purchase. :)