There are few hard and fast rules in life. As a physicist by education, I am even more aware of this than most. Most scientific "laws" are really just theories that survive 99.9% of challenges raised against them and thus haven't been disproved yet. And not for lack of trying. I spent a summer working at a Harvard/Smithsonian physics lab that was trying to disprove gravity (and by association, Einstein). Of all things, gravity. And they had been trying for 15 years.
Many laws and rules get to be infallible and the "truth" in a grand sense simply through repetition. Now gravity I'm generally willing to agree is a quality idea on the first telling - or skinned knee - but other things - what I'm going to call myths - do not get more true with age or retelling. They just get more...believed. And eventually the source for these myths is not Einstein, but "everyone says x" or "everyone does y." Will everyone please step forward and diagram their laws and/or rules on this here white board?
Instead, by being a student of the sport and pursuing opportunities like a USAT coaching license and long-term training camps, I've heard, read, and even tried the other sides of these myths. From my experience and experimentation, some stand to reason and others crumble in the face of a challenge.
Read what everyone says, consider the other sides (which aren't even limited to the ones I present here), and decide for yourself.
** Order of long bike and long run
Myth: Long bikes should be completed before long runs. In this order, legs will be sufficiently tired to replicate running long off the bike in an IM and the fitness gained with be "IM fitness."
Another side: A successful IM marathon comes after a conservative IM bike, below the competitor's level of bike fitness. In order to build better bike fitness and thus better IM fitness it is bike training which should be completed in a fatigued state.
Another side: If every long run is completed on fatigued legs, the athlete does not have the chance to build good run fitness because they are never running at a pace or aerobic capacity close to their capabilities.
Another side: Chronic fatigue is what the athlete feels the day after a long ride. Running through chronic fatigue is a good way to become injured. Acute fatigue is what the athlete feels immediately after a long ride. Running through acute fatigue is a good way to be prepared for the race. If you are going to train for the race, train for the race and run (short off the bike) through acute fatigue. Otherwise, do your long runs on the day when your legs are the freshest to avoid injury get the best aerobic bang for your training buck.
Another side: The week's longest ride and longest run should be separated by at least one day.
** Doing flip-turns in the pool
Myth: Triathletes do not need to learn how to do flip-turns because open water swims do not have walls every 25 yards
Another side: It is true, open water swims do not have walls. But nor do they have reach-pause-tuck-push-reach (aka an open turn) every 25 yards. Open turns interrupt a swimmer's stroke and breathing every 25 yards. Even ugly, flip-turns teach breath control and a streamlined body position, and as the turns improve, interrupt a swimmer's stroke less and less.
** Lateral stretches and mobilizations
Myth: Lateral leg-swings and grapevines should be part of a comprehensive warm-up routine to loosen up the adductors, abductors, and minor gluteal muscles.
Another side: The above structures plus the hips, abdominals and pelvic floor are the main structures that stabilize every single pedal stroke and foot strike. Loose stabilizers lead to poor form, and in some ways prevent good form, and cause smaller stabilizers (muscles, ligaments, tendons around the ankle and knee) to bear the brunt of all that force. Ouch.
Another side: There is a difference between tight muscles and taut muscles. Tight impedes performance by limiting mobility; taut enhances it by returning energy and literally putting the spring in your step. Something can be done about tight - light stretches, epsom salt baths, training sessions with appropriate warm-up and cool-down, massage; nothing should be done about taut - and it should be fought to be protected.
** Compression gear and massages
Myth: Compression gear slows muscle break-down during training and racing (by preventing muscle jiggling) and improves recovery post-training and -racing (by increasing blood flow and oxygenation). Massages remove lactic acid from well-used muscles.
Another side: Depending on who you ask, no scientific studies yet completed prove that compression gear does anything - except making its wearer look like a dork. A recent scientific study discovery that the lactic acid removal of massages was much less than anticipated, perhaps even completely nothing.
Another side: Compression gear makes my feet, calves, and legs feel better. Massages definitely make me feel better. I don't care if they solve world peace, the math is simple: a lot of what I do to my body does not feel especially good and compression gear and massages make me feel better. I'll deal with looking like a dork.
** Barefoot running
Myth: Every runner will be the best runner they can be, with the best form with which they can run, when they run barefoot.
Another side: With the increased incidence of barefoot running has come an increased incidence in running injuries. Something like a 57% increase in incidence. Despite what Born to Run implies not everyone is evolved to run barefoot. Or maybe I should say some people have evolved too far to run barefoot.
Another side: It can feel good to the bottom of the feet (like a massage and we know how I feel about those). Try it gently on a grassy field or astroturf.
Another side: My form changes very little when I run barefoot. Where I feel it is in my arches, ankles, and shins: those long-forgotten stabilizers side-lined by orthotics and trainers are finally having to do their jobs. And for that reason, I do it from time to time to keep my body honest.
My job is to be an athlete and a coach and I find I can't do it without being a student as well. A student that looks at all sides, considering all the things that make people stronger, faster, and more efficient. I rarely believe everyone the first time around and I recommend you do the same...unless everyone goes by the name Einstein. I have a feeling those guys at Harvard are going to be at it for a long time.