By Kari Studley PT, DPT and Erik Moen PT
Did you miss “Bike to Work Day/Month”? Whether you did or not, now is the perfect time to commit to a bike-commute. The logistics of bike commuting include things such as what to do with your bike clothes, bike parking, how much stuff (clothes, computer, food, etc) you can bring, how to carry your stuff, hygiene, tools, etc. This article will evaluate how you carry your stuff to work. We will review the most popular methods (backpack, shoulder bag, and pannier). The load you chose to carry can have a significant impact on the body. Your choice of how much stuff you will carry and how you carry it will be affected by your musculoskeletal tolerance of load.
Weight: Limiting the amount you carry can make your commute more enjoyable as well as easier on your body. While you will want to make sure you have the essentials for work and biking, do you really need to carry it all every commute? Look for ways to lighten your load by leaving a ration of clothes and food at work, try transporting digital data on a portable drive rather than transporting a laptop. Research that studied children and backpacks found that pressures on the shoulder as a result of carrying 10% of their body weight through a backpack or shoulder bag was more than the minimum amount to occlude skin blood flow.1 Basic point is that it doesn’t take much extra weight to add unnecessary strain to your body while bike commuting.
Anatomical Considerations: The main regions of concern with backpacks and shoulder bags are the shoulders, neck, and upper/lower back. Backpack and shoulder bag straps can compress sensitive nerves, arteries and muscles in the shoulder and armpit regions. A nerve which runs on the top of the shoulders and provides upper shoulder sensation (supraclavicular cutaneous nerve) can become injured as a result of carrying a heavy load on the shoulders. Excessive exposure to load at the neck, upper back, shoulder blade, and shoulder musculature can create strain injuries. This is a result of carrying bags that are just too heavy or create asymmetrical/irregular loading to the body.
The Backpack: A backpack balances the load on both shoulders in a symmetric fashion. Backpacks have the potential to create muscle strain, nerve irritation and limit blood circulation. The use of chest and hip straps can help offset some of the direct weight bearing to the shoulder region as improve the stability of your load. The position of your backpack on your back can contribute to commuting discomfort. Scientific research of backpacks and children is so far inconclusive with regards to ideal pack position on the back (high vs. low) and its association with pack-related symptoms in standing. Bicycling requires a forward bent position. A lower position of the backpack may be more ideal in regards to preventing low back strain as it is closer to your center of gravity. There is a lack of research in backpacks and adults and none that we know of with adults wearing backpacks in the bicycling position.
The Shoulder / Messenger Bag: This style of bag is generally worn over one shoulder through a single strap. The asymmetric nature of a shoulder/messenger bag places unequal strain on the shoulders, neck and back. It also results in altered cycling biomechanics as the body tries to compensate for the uneven weight distribution. It has also been found that perceived pain was significantly greater in children that used a single shoulder strap bag (compared to a backpack).1
There are some extra features that you may want to look for in a shoulder bag to improve cycling ergonomics and comfort. Extra padding on the shoulder strap may help improve comfort and alleviate centralized pressure on the shoulder. An additional lower strap that crosses the abdomen will also help relieve pressure and better secure the bag – an important safety factor while cycling!
A general safety consideration with shoulder bags is to ensure that your visibility is not obscured by the bag. If you have to turn your shoulders and trunk significantly to see over/past your bag, consider modifying the position of the bag on your back, carrying less stuff, a smaller bag, and/or an alternative carrying method.
Panniers and Rack System: Panniers are bags that attach to front and/or rear mounted bicycle racks. Panniers place the burden of load on your bike rather than your body. Imagine less weight/load at your saddle and handlebars. Imagine improved trunk and neck motion. Not all bicycles can take racks. Racing-style bicycles do not typically have mounting brackets incorporated to their frame. Have your local bicycle shop help you assess your bicycle’s rack-compatibility.
Any pre-existing chronic neck and back issues can be further exacerbated by bicycling with backpacks and messenger-style bags. Heavily loaded bikes will create extra stress and strain to legs and back. You may need to adjust your gearing to best tackle your commute route. Bike commuting should be an enjoyable extra dimension of bicycling and health promotion. Do not hesitate to consult a qualified health practitioner, such as a Physical Therapist, to further assess your cycling biomechanics and ensure your commute stays pain free and safe!
References: 1. Macias B, Murthy G, Chambers H, Hargens A. Asymmetric loads and pain associated with backpack carrying by children. Journal Of Pediatric Orthopedics [serial online]. July 2008;28(5):512-517. Available from: MEDLINE, Ipswich, MA. Accessed May 8, 2010.
Kari Studley PT, DPT has been a Physical Therapist since 2006. She races mountain bike and cyclocross professionally and has been bike commuting for over 10 years. Kari is working at Corpore Sano Physical Therapy in Kenmore as a treating physical therapist and bicycle biomechanist. Contact Kari by visiting www.CorporeSanoPT.com.