Shoulders and Overhead Work

Why this matters

Shoulder injuries from overhead work are slow, stubborn and expensive. A worn rotator cuff tendon does not heal well, surgery to repair one can mean months off the tools, and a shoulder that hurts raising a drill also hurts on a ladder, on a winding bar and lifting a box onto a van shelf. Overhead work is unavoidable in electrical, HVAC, garage door and much plumbing and remodeling work, but the amount of it any one person does in a day is something the shop decides, usually without noticing it is deciding.

Why arms-overhead injures the shoulder

The rotator cuff is a group of four muscles whose tendons wrap the ball of the upper arm bone and hold it centerd in the shallow shoulder socket. One of them, the supraspinatus, runs its tendon through a narrow gap between the top of the arm bone and a bony shelf above it (the acromion).

Raise the arm and that gap narrows. Through the middle of the range, roughly when the elbow passes shoulder height, the tendon is squeezed against the shelf; repeated and sustained, that pinching (impingement) inflames and frays it. Three more things make overhead work worse than the same effort at waist height:

• Poor blood supply. The part of the tendon near its attachment has a thin blood supply, and a muscle held contracted squeezes its own vessels. A static overhead hold starves the tissue that most needs feeding.
• Static fatigue. A muscle held at a high fraction of its maximum effort fatigues in about a minute; low-level efforts can be held much longer. Holding a tool overhead sits uncomfortably high on that curve, and a fatigued cuff stops holding the joint centerd, which narrows the gap further.
• The arm itself is a load. A whole arm weighs roughly 5 percent of body weight, centerd partway down its length. Held straight out or up, it loads the shoulder before you pick up anything.

The research on overhead workers finds risk rising with the cumulative time spent with the upper arm raised high, over months and years, rather than with any one bad day. That is the same accumulated-load pattern behind most strain injuries. See related: How Cumulative Strain Injuries Actually Develop.

Tool weight is a lever, not just a weight

What the shoulder feels is the tool's weight multiplied by how far it is held from the shoulder joint. That turning force is called torque.

Take an illustrative 5 lb drill:

• held at full reach, about 24 in from the shoulder: 5 x 24 = 120 inch-pounds;
• held with the elbow bent, about 12 in from the shoulder: 5 x 12 = 60 inch-pounds.

Same drill, half the load, from bringing the work closer. Now add the arm: a 180 lb person's arm weighs around 9 lb at about 5 percent of body weight, with its center roughly 11 in from the shoulder when straight, so about 9 x 11 = 99 inch-pounds on its own. At full reach the shoulder carries roughly 120 + 99 = 219 inch-pounds; elbow bent, the tool's 60 plus a smaller arm term, since a bent arm's center sits closer to the joint. The arm alone is comparable to the tool, which is why a lighter tool helps but bringing the work closer helps more. These are rounded figures to show the method, not a calculation for a specific person.

Practical consequences: use the smallest battery that will do the job overhead; the big pack belongs on the bench. Use a drill stand or extension pole that pushes from the floor for repeated ceiling holes. Hold tools close, with elbows bent and below shoulder height wherever the work allows.

Where the hands should be

 SIDE VIEW, STANDING: WORKING HEIGHT ZONES

 hands above the head ........ AVOID for more
                               than brief tasks
 ------------------------- top of the head
 hands head to shoulder ...... LIMIT; count
                               these minutes
 ------------------------- shoulder height
 hands shoulder to waist ..... BEST; elbows in,
                               tool close
 ------------------------- waist height
 hands below the knee ........ move the work
                               or kneel/sit

A platform moves the person up, so the work drops a zone relative to the body. For work on a ceiling plane you rarely reach the best zone, because your head hits the ceiling first, but going from arms fully up to hands at head height with elbows bent cuts both the angle and the lever.

Platforms and stands

• Platform ladders and podium steps give a standing surface with a guardrail, so you can work facing the job rather than leaning off a stepladder. They are what makes "get closer" possible on most residential ceilings.
• Rolling scaffold for long runs of ceiling work, such as a basement full of duct hangers or a run of recessed lights.
• A stepladder's top cap and the step below it are not standing surfaces, and overreaching sideways off any ladder is how a shoulder strain becomes a fall. The ladder rules sit in 29 CFR 1910.23 for general industry and 29 CFR 1926.1053 for construction work.

The rule and two cases

A shop default to start from: drop the arms to the sides at least every couple of minutes during overhead work, and cap each person at about an hour a day of hands above shoulder height, then rotate the overhead tasks to someone else. Tune it to your crews. Here is that hour-a-day gate applied to two jobs that resolve in opposite ways.

Case A: the electrician who could change the work

A two-person electrical crew installs 14 ceiling fixtures and 22 smoke alarms in a remodel, working from 6 ft stepladders. Illustrative overhead minutes per item: 8 for a fixture, 3 for an alarm. For the lead, who does all of it: 14 x 8 = 112 minutes plus 22 x 3 = 66 minutes, 178 minutes overhead, nearly three times the hour.

Changes:

• Pre-assemble at the bench. Mounting brackets, pigtails and alarm harnesses made up at waist height before anyone climbs. That roughly halves the time spent overhead: 4 minutes per fixture, 2 per alarm. 14 x 4 = 56 plus 22 x 2 = 44, 100 minutes.
• Swap the stepladders for a podium step, so the work sits at head height with elbows bent instead of at full reach. That does not change the minutes, but it cuts the load in each one.
• Split the overhead work between both techs. 100 minutes split evenly is 50 each, under the hour.

Outcome: the job design changed and the gate is met without changing the schedule.

Case B: the garage door tech who could not

A garage door tech does torsion spring replacements: the spring sits on a shaft above the door at header height, and the winding, bearing plates and cable drums are all overhead. Illustrative figure: about 18 minutes of hands-above-shoulder time per spring job. On a busy day he does 6, so 6 x 18 = 108 minutes.

Changes:

• Position the platform so the spring is near shoulder height for the winding, which is most of the effort. Cable drums and the end bearing plates stay overhead. That brings it to about 12 minutes a job: 6 x 12 = 72 minutes, still over the hour.
• Pre-assembly does not apply. The spring goes up already assembled; the overhead part is the install.

What is left is the schedule. At 12 minutes a job, 5 jobs is exactly 60 minutes, and a day that runs long on even one job puts him over, so the dispatcher caps spring jobs at 4 a day per tech (4 x 12 = 48 minutes) and fills the rest of his day with ground-level work: panel replacements, bottom seals, tune-ups. Opener installs are ceiling work too and count against the same hour. Outcome: the gate is met only by changing who does what, not how.

The point of running both: the same rule sent one job back to the bench and the other to the dispatch board. A shop that only knows the first answer tells the garage door tech to "use better form" and keeps booking him six spring jobs a day.

Early signs, and when to see a doctor

• An ache at the top or outer side of the shoulder that comes on during overhead work and eases after
• Pain through a middle arc of raising the arm, roughly around shoulder height, that eases as the arm goes higher (the arc where the gap under the shelf is narrowest)
• Clicking or catching in the shoulder on the way up, or reaching for the top van shelf with the other arm without noticing you have started doing it
• Pain at night, especially lying on that side, and weakness raising the arm or holding it out: see a doctor, and tell them how much overhead work you do, in minutes a day and with what tools.

Night pain and weakness can mean a tendon that is tearing rather than just inflamed, and a tear treated early has more options than one found after a season of working through it. A shoulder that suddenly cannot lift after a jolt or a fall needs to be seen promptly. See related: Talking to a Doctor About What Your Job Actually Involves, and The Early Discomfort Report SOP.

Rotation is a design tool, not a favor

Rotation only works if overhead minutes are treated as a scarce resource the dispatcher allocates, the way drive time is. Write the overhead-heavy tasks into each role's physical demands description so it is visible which roles carry them and how much. See related: Writing a Physical Demands Description for Each Role. And watch who never gets rotated: the most experienced tech is usually the one who does all the overhead finish work, because they are fastest at it, which is how the best tech on the crew ends up with the worst shoulders on it.

References

• 29 CFR 1910.23, ladders (general industry); 29 CFR 1926.1053, ladders (construction)
• NIOSH, "Musculoskeletal Disorders and Workplace Factors" (DHHS NIOSH Publication 97-141), shoulder chapter on posture and repetition
• See related: How Cumulative Strain Injuries Actually Develop; Writing a Physical Demands Description for Each Role
• See related: Talking to a Doctor About What Your Job Actually Involves; The Early Discomfort Report SOP