There are essentially 4 types of sprayers on the market these days for weed control. Since this article focuses on Ergonomics, keep in mind that I will be talking about the product design rather than the chemicals involved.
The four sprayer types differ on weight, hand strength requirements, need for repetitious movements, and grip posture, but most are available for all major brands of weed control product.
For many people, the choice is a preference rather than a real concern. Massive attention to weeds usually happens once or twice a year, for an intense weekend or two – sometimes three.
For some people, the choice of product design can make the difference between intense and long – lasting pain and a controlled increase in activity.
Muscles like it better if you can ramp activity up – starting with a short period of a half hour to two hours in a day (depending on your present condition), and gradually increasing. If you have a lot of arm / wrist / hand issues, it may be better to hire a gardener for most of the work.
BASIC SPRAY BOTTLE
Every spray bottle has issues. Due to the position and balance of the liquid container, you have to hold the weight against gravity while simultaneously using the finger flexors to activate the pump. If your wrist or fingers are weak, maintaining a good position may be difficult. How much stress this creates depends on the weight of the bottle and the resistance of the mechanism. If you have a lot of weeds, this may be a real problem.
For each spray, the force involved may not seem like much, but with the wrist muscles stabilizing the bottle, force comes from finger flexors. These are not particularly strong. If there are already flexor tendon or muscle issues, endurance for this activity may be very limited.
An additional point is that there is no sustained spray with this design. It only lasts for a second or less. Your gain in area per muscle contraction is low.
Although in the best spray bottle designs, three to four fingers are involved in the pulling the trigger, this type of activity can also irritate trigger finger.
PULL AND SPRAY
There are some good aspects to the Pull and Spray containers. Since the liquid container is not attached directly to the sprayer head, it can be either held in the other hand or placed on the ground or on a table. This alone makes the task easier and should increase endurance for the action.
The sprayer heads have two designs:
• Spray Bottle style: The trigger is separated from the handle. This is not recommended as it forces a wider grip and more restrictive finger position.
• Trigger built into Handle: The type is recommended. It generally requires lees force. Spray is activated by slightly tightening the grip. The ones I have tried are very low force.
Models from 2010 produced weak and short-lived streams of liquid. 2011 models show improvement in this area.
Setting the sprayer head for action requires slowing pulling a ring attached to the bottom of the head. The design of the head is problematic in some models.
Although I enjoy the length, size and heft of the head on the Round Up version, the most natural way to hold the head while pulling the ring positions the non-dominant wrist bent towards the little finger and flexed beyond 15°, using force while in an awkward posture.
The work around is to turn the head around in your grip, so that the nozzle points downward before beginning the pull. Then hold your wrist steady, making sure it doesn’t flex forward. This allows the wrist to remain in a neutral posture. I have not tried this year’s version of the Ortho, so I’m not sure about it, but from what I have observed, the same directions apply.
Because a forceful elbow extension is required, there is a chance of irritation if you have epicondylitis, however there is only a 6 inch movement so this is minimal. Watch your posture.
The pump sprayer is available in several sizes, and is probably the best choice for wrist position if you remember to keep it straight rather that let it fall into flexion when you pump. It also has the longest spray action., so it requires fewer pumps to cover the same territory.
This again has the advantage of the spray head being separate from the liquid container. Here, however, the handle on that container is not as well designed for carrying. These bottles do come in different designs, so if you choose to go with the pump sprayer, you may want to look around for one that will really suit you.
HOSE POWERED LIQUID
Gadgets of different kinds are available that attach to your hose. They have benefits and problems (just like everything else). Most of these require a moderate strength sustained grip for the duration of the spray (more than the other products).
Another drawback is the powered hose (e.g. filled with water under pressure) that you need to bring with you and manipulate into the proper position for reaching your target. This can be a problem if you have shoulder or wrist issues. You may be able to successfully wear light wrist supports for this task.
The only other issue I have run across with these is that they are frequently not very pin-pointed in their targeting. You may spray more than you intend to.
Please let me know if you have any questions.