In Book 1 of “The Iliad,” when Achilles and Agamemnon quarrel over a question of honor, one of the first to attempt to speak reason is the aged warrior, Nestor. Though shown some deference, neither party is keen to accept Nestor’s wisdom–one almost gets the sense that they’re humoring him as they do often later in the poem.  To be fair, Nestor can go on a bit, and is quick to throw his age and associated experience at his junior colleagues. The thing is, Nestor was right–had Achilles and Agamemnon listened to him the problem would have been solved. Of course we wouldn’t have the poem either. In fencing we have a wide variety of Nestors. Sometimes it is a gimpy limb clamoring via pain to remind one that it might be best to stop a drill or sit out the next bout. Sometimes it is an elder fencer or an even older master. If we’re really unlucky, Nestor may take the form of one’s physician.
Achilles chose glory and a short life over less fame and a long one, and many fencers are the same. In one’s teens, twenties, even thirties one can still do many things one maybe shouldn’t, but since recovery time is relatively fast, since one is still nimble, strong, etc. it’s easier to go for broke and relegate any worry to later. I’m a good example. As a younger person, say 17-35, I could fence for hours; I fenced several days a week; any injury was normally minor and healed quickly; and I took chances that only those without larger responsibilities take, such as fencing with 3-4lb sabres and only a brass stirrup guard to protect the hand (or fail to protect it as I found out once).  There is no round-trip ticket to yesterday, so hindsight is as useless as it can be painful. However, like a Nestor, meaning I realize that neither Achilles nor Agamemnon are likely to listen, I feel compelled to encourage anyone keen to fence into their dotage to be mindful of their choices and take care of themselves. Cultivating sense at a younger age is tough, but ideal–the sooner we take care of ourselves, the longer we’re likely going to be able to fence.
Conditioning, Stretching, and Rest
We’re less likely to be injured if our over-all health is decent. If we eat right, exercise regularly, and maintain decent cardio everything is easier. For those keen to lift weights, fine, but for fencing you don’t need to be a body-builder or circus strongman. It’s better to build useful, appropriate strength than attempt to be yet another six-pack clad wanna-be model.  There are a number of resources for diet and exercise–if all else fails ask your doctor.
Stretching before and after fencing is important. Normally we warm up a bit, then stretch. None of this needs to be strenuous, just enough to keep you limber and less likely to pull or tear anything. Here too, it’s unnecessary to do the splits–don’t push anything, even a stretch, too far.
Equally important is recovery time. Our bodies need rest after exercise, and if we push past rest we only increase the chances of injury. This could mean tearing your ACL or striking an opponent too hard. Take breaks. It’s a fencing class, not boot camp, and no instructor should push anyone beyond reason. Likewise, no instructor should ever shame anyone for taking that break, being unable to do a particular exercise, or anything else. There are usually alternatives to many stretches and a decent instructor will suggest one of those if possible.
Injury and Recovery
If you end up with an injury take care of it. Happily, injuries are normally few and far between in fencing provided one isn’t a knucklehead. Wear your protective gear, observe the safety rules of the sala, and look out for one another. Most injuries occur because people fail to heed safety precautions, or they’re mucking about, or they purposefully disdain safety protocols out of some he-man notion of toughness.
For anything beyond the occasional bruise it’s often wise to see a medical professional. A deep cut, a stab wound, a potential concussion, a broken bone, a torn or pulled muscle or ligament, anything like this could have serious consequences. See a doctor, and see a proper one, one with MD behind their name, not one of the many purveyors of pseudo-science. 
Give yourself time to heal. I once sprained my ankle the night before a tournament, but being 21 just wrapped it tightly and fenced anyway. That wasn’t smart. If we start training before an injury heals we run the risk of making it worse, but sometimes we also ensure that we keep that injury for the rest of our lives. Most of the joints on my right side are compromised in some degree, and some of these injuries, such as tennis-elbow, could have been alleviated by dealing with them properly at the time.
Age: It just plain SUCKS
Age in some degree is relative, but as a general rule the older we get the longer it takes to heal, the more recovery time we need, and much as we might hate it we slow down. It sucks. I know because I’ve fenced for over three decades. IF we want to keep fencing until we literally cannot, then we have to be cognizant of our choices early on.
Somethings, alas, are just a younger person’s game. Longsword, for example, one “can” do as an older person, but one probably shouldn’t. It’s one thing to dabble with another old codger or take the occasional seminar, but it’s less wise to enter tourneys at a certain age. They can be rough, and tough as some old people are the simple fact is that they break more easily. No 20 or 30 something is going to take it easy on you, and if they did, you’d only be insulted.
This can be super hard to accept when we really love something. In the past year or so I’ve realized that the clock is ticking for me and using appropriately weighted historical sabres. I “can” fence with them, and still do, but not as often as I did, because much as I miss it if I continue to use them all the time I won’t be fencing any sabre down the road. When this happens we have to make some difficult choices. I teach more than I fight now, I often use lighter sabres (such as the S2000 Olympic with kids), and I focus on other weapons I enjoy.
For example, though I’ve always read up on and dabbled in smallsword, it’s increasingly becoming one of my chief studies.  The others are largely related to it, such as late period rapier and smallsword’s 19th century descendent, epee. They don’t have the flash and fire of sabre, and I miss that, but they share the same intellectual aspects, rely on similar strategies, and even include, epee excepted, some of the more physical options in sabre and broadsword. Weapons seizures, for example, add a bit of spice.
The Take Away
Fence, and fence hard, but be smart. To me, the best approach is a middle-way, something between Sterne’s health miser and Blake’s supposed palace of wisdom. This is to say that we don’t want to be so careful that we’re bored and learn nothing–the Art is about fighting and thus must be practiced–but nor do we want to fight like our lives depended on it each and every time. Moderation will serve most of the time.
Whatever one fences, it pays to be aware of the wear and tear on your body, because it is a pain delayed. We pay for the fun of our 20s in our 40s, and it’s all downhill after that. If you don’t plan to fence into your 90s, cool, then go nuts. If you do think you might enjoy fencing until you drop, and you’d prefer not to do it from a wheelchair or from behind a walker, then maintain your health, fence responsibly, and let that ligament heal no matter how long it takes.
 Cf. “The Iliad,” Book 1, ll. 318ff
 In the age before better gloves, a guard that turned in a sweaty grip or broke could mean a trip to the ER. Pinky nails, btw, do grow back, but it takes months.
 I know a lot of people keen to lift, and some may be unhappy with this statement, but I stand by it. Unless one intends to wrestle a fair amount, where size and power mean more, any weight-training for fencing shouldn’t focus on bulk.
 This may also offend, but chiropractors, some massage outfits, and others are not doctors. In the PNW I have found that a lot of people go to chiropractors–I’m not sure why. While I’m sure there are some who provide what is probably decent massage, the “science” behind their practice is dubious. See for example:
 The first work on fencing I ever bought was a facsimile copy of Domenico Angelo’s The School of Fencing (1763; 1787); I found it at a used book store in 1986.