How to schedule strength and yoga around endurance

Your muscles are made of thin strands called fibres. There are two kinds. Slow fibres keep going for hours. Fast fibres contract quicker and harder, and run out sooner. Every fast swing, jump and sprint runs on the fast ones.

Both kinds burn glycogen, the sugar stored in your muscles. In 1974, researchers had men ride a bike at different efforts and took small samples of their thigh muscle. At a low effort, the slow fibres did the work and emptied first. The fast fibres joined in as the slow ones ran dry. After three hours, the slow fibres were nearly empty, and almost all the glycogen left was in the fast fibres.

A short base session barely touches your fast fibres. A long base session reaches your fast fibres once the slow fibres run low. So when you plan your week, a long session counts as a hard one. Threshold draws the fast fibres in, and VO₂max and sprints use them from the first minute. If you eat enough, your fast fibres take about a day to fill up again.

Hard work also weakens the signal that makes a muscle pull. Each muscle keeps a little calcium stored inside it. When a nerve tells the muscle to pull, the calcium is released, and the calcium is what starts the pull. After hard work, each nerve signal releases less calcium, so the muscle pulls less hard. That lasts for some hours. Low glycogen makes it worse, because less calcium is released when the glycogen stored beside it runs low.

Running adds damage. Each time your foot lands, your legs brake you, so the muscle is stretched while it pushes. Over a long or hard run, all that braking leaves small tears, and you often feel them most a day or two later. After a race or a very long run, your legs can take four to eight days to recover fully.

The quick fuel for the first seconds of a sprint comes back within minutes. The calcium signal takes hours, your fast fibres a day to refill, and torn muscle days.

A short base session tires mostly your slow fibres. Intervals and long sessions tire the fast ones too. When your fast fibres are empty, short of calcium or torn, the whole muscle switches on more slowly and lets go more slowly. And the faster it has to move, the more force it loses. Power is force made fast, so it drops further than strength does.

Researchers tested well-trained runners after a marathon. Five days later, their jumps still had 12 percent less power. Yet they pushed off the ground just as hard as before the race. They could push as hard. They could not push as fast.

Most of what we know about this comes from jumps, sprints and barbells. The swing behaves the same way. In one study, 16 men who knew the swing well did rounds of all-out swings. As each round went on, their hips slowed and each swing took longer, yet they pushed into the ground as hard as at the start. A fast swing runs on the same fast fibres as a jump, and it slows the same way when they tire.

Slow work is different. In a slow squat, a carry or a long hold, other fibres take over as some tire, and nothing has to happen in a split second. The same tiredness costs a carry far less than a swing.

A tired power session is not wasted. It builds something else.

In one study, 64 trained men squatted twice a week for eight weeks. Some stopped each set as soon as the bar began to slow. Others kept going until it moved 40 percent slower than on the first rep. Every group got just as strong. The men who kept going grew more muscle, but their thighs ended up slower to switch on.

When researchers put 19 training studies together, they found the same pattern. The more a set was allowed to slow, the more the muscle grew, and the less jumps and sprints improved.

In those studies, the reps slowed because the set went on. A swing slowed by last night's intervals is a slow rep too.

So tired swings still build strength and some muscle. What they build less of is spring, the quick stretch and recoil that throws the bell up, and spring is what you came for. One tired swing session costs you little. Tired swings every week move you towards slow strength, and turn some of your fastest fibres into a slower kind.

On a tired day, the better choice is structure: slow, heavy work that holds your shape under a load, like squats and carries. It needs force, not speed, so the tiredness costs it little.

Power never shares a day with threshold, VO₂max, sprints or a long session, in any sport. It does not go on the morning after one either. That morning your fast fibres may still be refilling, and after a run your legs are still mending.

You stop each set while every rep is still fast. And you can spread the work over more days without building any less power. Women footballers who did the same week of jumps in two sessions instead of one gained as much as those who did it in one. Teenage boys who split theirs over three sessions gained as much as boys who did it in one session, and were far less sore. Less soreness makes power easier to fit beside your runs, rides and swims. So you do a little power on several days of the week.

On a day that also has a base session, the bells go first. You come to them with your fast fibres full, and the base session after them runs mostly on slow fibres anyway. Do the base session first, and your swings start a little slower.

A review gathered studies that tried both orders on the same day. People who lifted before their endurance session gained more strength in moving lifts than people who lifted after it. In held positions, the two gained the same. The lifts in those studies were heavy and slow. A swing loses more to tiredness than a slow lift does, so it has more to lose by going second.

Structure can take the morning after a hard session, the day power cannot use. It never goes on the same day as a hard session.

Structure is no good when you are spent. Very tired muscles hold your shape badly under load. In one study, 25 men and women who lifted regularly did a punishing workout with 55 back squats in it. As the workout went on, their squats changed shape. Their knees bent less, and they leaned further forward. Practise structure like that and you train the wrong shape. Tired from last night is fine. Spent is not.

Structure also leaves your legs tired for the next day. Heavy work makes the muscle sore, most of all the slow lowering half of each lift. In one study, 14 trained runners did heavy leg lifting and a run on the same day. The next day, they gave out at a hard pace a minute or more sooner than when they were fresh. When they had lifted before running, the next day's running also cost them more oxygen.

The soreness shrinks once the work is familiar. The first time, heavy lowering work left strength at 86 percent two days later. Two weeks on, the same work barely dented it. But your legs still come to the next day's hard session tired.

In one study, 15 active men rode hard intervals on a bike. Afterwards, their squats got slower, but their bench press did not. Tiredness stays in the muscles a session used. So which sport you did matters, as well as how hard you went. A ride or a run leaves your arms and shoulders fresh.

A ride works your thighs. Pedalling pushes without braking, so it leaves little damage. But your thighs are the very muscles a squat or a jump needs, so a hard ride slows them, as it slowed those squats.

A run works your calves and thighs, and every stride lands. At running speeds, your calves take most of each landing, and much of the damage. After a race or a very long run, that damage is why your legs need more than a day.

A swim works your arms and shoulders. In front crawl, the legs add only about a tenth of your top speed. So a base swim leaves your legs fresh.

Yoga builds range and balance. Range is built by holding a position for a long time, like a long fold or a deep squat, and then by working at that new length. The long holds work best when the muscle is relaxed, not working at all.

Part of what resists a stretch is the muscle itself. Inside it sit tiny sensors called spindles. Stretch the muscle quickly and they fire, and the muscle tightens against the stretch. That is the stretch reflex. It is why you move into a long hold slowly and keep still there. Bounce into a stretch, and the muscle tightens on every bounce.

The rest is the tissue in and around the muscle. Researchers held people's hamstrings at a fixed stretch for 90 seconds. The resistance fell by about a third, while the muscle stayed fully relaxed. It fell the same way in people with a spinal cord injury, whose muscles cannot tighten at all. The give came from the tissue itself.

After one session you can reach further, but most of that gain is not new length. What changes is the point where the stretch starts to hurt. It starts to hurt later, so you go further before you stop. Then you work in that new position, so you get strong there too.

A long hold also leaves the muscle relaxed for a while after you stand up. A long stretch turns down the signals from your spinal cord to the muscle, so the muscle stays slack. A swing or a hard stride needs the opposite, a full burst of signals at once. So the long holds go after the bells and after the endurance session, or on a day of their own. They never come right before power or a hard session. A short moving flow is different. It holds no position long enough to leave the muscle slack, so it can go before a run or a swim.

Balance is a skill. Signals from the soles of your feet, your ankles and your eyes tell you where you are, and small, quick corrections go back to your muscles. Each one is a catch, and practice makes the catch quicker and finer. To learn them, you need clear signals, and tiredness blurs them.

A review of the research found that hard exercise above threshold makes people sway more, and long sessions at lower efforts can too. When your muscles are tired, the signals about where your joints are get less precise, and the corrections that come back are rougher.

Worse, what you practise tired, you learn less well, and the cost lasts for days. In one set of experiments, adults learned to control how hard one hand pressed. Those who tired the hand first learned at about a quarter of the rate. The next day they were rested, and still behind. They caught up only on the third or fourth day. Part of the problem was in the brain, not the hand. Balance is a skill of controlling force too, so it is best practised fresh.

So balance goes on a fresh day. It never comes straight after a hard or long session, while your legs are still tired from it.

Here is one week with two hard sessions: VO₂max intervals on the bike, and a long run a few days later. Each of the other days has a base session.

The week opens on a fresh day. Power comes first, then a base swim, then balance.

The next day brings the intervals, and your legs come to them at their best. That evening, you do a long range session.

The morning after the intervals, you leave the swings alone. You carry and squat slowly instead, then go for a base run.

The day after that, you are fresh again. A few fast sets of power come before a base ride, with range after it.

The day before the long run, you do power again, then a base swim. A few fast sets leave little behind. Heavy structure here would have cost the long run something.

The long run has range after it. The day after the long run has no power. You swim at base, and your shoulders do the work while your legs rest.

None of this asks you to train less. Each session moves to the day when the part of you it needs is ready, and away from the day that would spoil it. A session on the wrong day still builds something, just not the thing you did it for.

So on the morning after hard intervals, pick the bell up and carry it. On a fresh morning, swing it, and watch it float.