Men shave their legs for reasons that predate any grooming trend. Road cyclists, competitive swimmers, triathletes, bodybuilders and some runners all do it, and in each case there is a specific practical problem being solved rather than a look being chased.
The method is not the same as shaving a face. Two legs carry many times the hair of a jawline, the skin over a shin behaves nothing like the skin behind a knee, and blade wear becomes the limiting factor rather than an afterthought.
The actual reasons, sport by sport
Road cycling. A crash at speed grinds gravel into the skin of the hip, thigh and calf. Cleaning that wound is faster and less painful on bare skin, dressings adhere properly, and removing a dressing from hairy skin tears the scab off with it. Riders also get frequent sports massage, which is uncomfortable through leg hair. Aerodynamic gains from shaved legs have been claimed in wind tunnel work, and even if real they are marginal next to the wound care argument.
Swimming. Competitive swimmers shave down before a target meet. Part of the effect is drag, part of it is a documented increase in skin sensitivity to water that swimmers describe as feeling faster.
Bodybuilding and physique sport. Muscle definition reads on camera and on stage only if the skin is bare. This is the one case where appearance is the whole reason.
Physiotherapy and taping. Kinesiology tape and rigid strapping do not adhere to hair, and removing them from hairy skin is unpleasant enough that most clinics shave the area anyway.
Trim first, then shave
Leg hair longer than about 5mm needs a trimmer pass before a blade. A razor pushed through full length hair clogs almost immediately, and a clogged blade pulls.
Run a body hair trimmer over both legs with a 3mm guard. That takes about five minutes and removes roughly three quarters of the hair volume, which is the volume that would otherwise have destroyed a cartridge in one session.
Then get in a warm shower for two to three minutes before shaving. Leg hair is coarse and hydration matters more here than on a face.
The three zones, and why they need different handling
Shins. The easiest area on the body to shave. Skin is thin and tightly bound to the tibia, so it does not move, and grain runs straight down. Long strokes work. This is where beginners get confident.
Knees and ankles. The hardest. Both are bony, both change shape depending on how you hold the joint, and both have skin that folds. Bend the knee to a right angle before shaving over the cap, which stretches the skin flat across it. For ankles, point the toes to tension the skin over the bone. Use strokes of about 3cm and expect to reposition constantly.
Thighs and calves. Large muscle, loose skin, and grain that changes. The back of the thigh in particular has hair growing at a shallow angle, often sideways rather than downward. Shaving straight down across sideways hair is the reliable way to produce razor bumps there a couple of days later. Map the direction first with the grain map tool.
Blade economics, which is the part nobody warns about
Blades dull in proportion to the total quantity of hair they cut, not the number of times you pick them up.
A cartridge rated for five to seven face shaves will start tugging after two or three full leg shaves. At a three to five day shaving interval that adds up quickly, and a pulling cartridge is also the cause of most leg nicks, because a blade that is not shearing needs pressure to work.
This is where a double-edge safety razor makes a straightforward case. Blades cost a small fraction of a cartridge, so you can fit a fresh one for every leg session without thinking about it, and a single sharp blade cutting at the skin surface produces fewer ingrowns than four blades cutting below it. The one adjustment is technique: a safety razor has no pivot, so on a knee you move the razor in short strokes and let your wrist do the angle. Razor choices are in best safety razor.
Direction, passes and pressure
Shave with the grain on the first pass, everywhere. On shins that is downward. On the backs of the thighs it may be diagonal.
A second pass across the grain is reasonable on shins and calves. Against the grain on legs is where people get into trouble, particularly on the thigh, and it buys very little because leg hair regrowing at a few tenths of a millimetre is not visible anyway.
Keep the pressure at the weight of the razor. Skin over the shin is directly on bone with almost no padding, and pressing there produces surface irritation quickly, the mechanism described in how to prevent razor burn.
Regrowth, and what maintenance actually looks like
Stubble becomes noticeable on legs at around day two and rough at day three. A maintenance shave every three to five days keeps it smooth and takes eight to twelve minutes once you know the terrain.
The prickle phase is milder than on a chest, because leg hair lies flatter and legs spend the day inside looser fabric. Socks are the exception: an elasticated cuff on freshly shaved ankles is where irritation shows up first.
If you stop, there is no penalty. Leg hair grows back at the same density it had before, because shaving never touches the follicle. The only change is the blunt tip, which disappears once the hair reaches its previous length.
When trimming is the better answer
If the reason is appearance rather than function, a 1mm guard gives you most of the effect with none of the maintenance. Legs at 1mm read as smooth from more than a metre away, there is no regrowth prickle, and there is no ingrown risk at all.
Shaving earns its place when something has to stick to your skin or come off it: tape, dressings, massage oil, a wetsuit. That framing is the same one that applies across the rest of the body in what is manscaping.
The short version
Trim to 3mm, shower for two to three minutes, then shave with the grain in one pass. Bend the knee and point the toes to flatten the bony areas. Expect a cartridge to last two or three sessions, which is the reason a cheap double-edge blade suits legs better than any cartridge. And if nothing needs to adhere to your skin, a 1mm trim does the same job with none of the upkeep.