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Upper Body Light is a month of unloaded arm and shoulder work done standing up. It targets your deltoids, upper back and arms with three movements that need no floor, no equipment, no jumping and no space beyond what you take up with your arms out. Every day can be done sitting down, which makes it one of the few upper body challenges that works from a desk chair, a wheelchair or a hotel bed. It is silent. It is difficulty 1 because nothing in it is heavy or fast. What it builds is endurance in the muscles that hold your arms up, plus a daily habit of moving your shoulders through their full range. It will not build size or serious strength and it is not meant to.

Two day types alternate and each has its own progression. Odd days are sets: shoulder taps and bicep extensions, 3 sets with 30 seconds of rest between them. The rep count starts at 40 of each and climbs in steps of 10, with every number held for three sessions before it moves - 40 for the first week, then 50, 60, 70 and finally 80 for the last week. Even days are one unbroken block of raised arm circles with no sets and no rest. Those climb by 20 every single time, from 60 on day 2 to 340 on day 30, and never plateau. There are no step-down days on this calendar. The odd days give you a breather by staying flat for three sessions at a time while the even days just keep going up.

How to do the exercises

Three exercises run through this challenge: shoulder taps, bicep extensions and raised arm circles.

• Shoulder Taps: stand or sit tall with your fingertips resting on your shoulders. Extend both arms straight up overhead then bring your fingertips back down to your shoulders. That is one rep. Reach all the way up so your elbows lock out and keep your shoulders down away from your ears rather than shrugging them up with every rep. Keep your ribs down and your back neutral instead of arching to get the arms higher. Arm raises to the front are an easier alternative if overhead reaching bothers your shoulders.
• Bicep Extensions: start with your fists at your shoulders, elbows bent and tucked in. Punch both arms straight out in front of you at shoulder height then pull them back. Keep the movement controlled in both directions rather than letting the arms flop back and keep your shoulders square so you are not twisting to add reach. Overhead punches are the harder swap and alternate sides so they also take a little longer.
• Raised Arm Circles: hold both arms straight out to the sides at shoulder height and draw small circles with your hands, about the size of a dinner plate. Count each full circle as one rep. Switch direction halfway through the day's number. Keep your arms level the whole time since dropping them below the shoulder line is what your body will try to do as it tires and it takes the work out. Smaller circles are harder than bigger ones. If your shoulders cannot manage the full count at height, arm scissors in front of your chest work the same muscles with less strain.

Adjust Difficulty

Make it easier: On set days, take 60 seconds of rest instead of 30 or drop to 2 sets. On circle days, split the number into two or three blocks and shake your arms out between them. Lowering your arms to about 45 degrees on the circles makes them much easier and is a fair place to start if 60 in a row at shoulder height already burns. Do the whole challenge seated if standing for the duration is the hard part. If your shoulders are sore from something else, shoulder shrugs can stand in for the circles on a bad day and keep the streak going.

Make it harder: Hold a can of food or a small bottle of water in each hand for every movement. It sounds like nothing and it is not. Cut the rest on set days to 15 seconds or run the three sets back to back. On circle days make the circles smaller and slower and add a 30 second straight-arm hold at the end with your arms out to the sides. Doubling the day's circle number turns the last week into something that will make your shoulders shake.

What to expect

The first week feels like a warm-up and that is fine. Your shoulders will notice the circles before anything else since holding your arms out at height for a minute or more is harder than it has any right to be. Expect a burn across the tops of your shoulders on even days and a mild ache in your upper back the next morning. The set days stay comfortable for longer because the reps only move every three sessions. From around day 20 the circle numbers cross 200 and the unbroken block becomes the hard half of the month even though the rating says 1. Your posture will likely feel a little taller by week three because the muscles that pull your shoulders back have been working every day. By day 30 you will hold 340 circles in one go, which most people could not do on day 1.