Feb 25, 2013 at 7:19 pm #1299719
@robertm2sLocale: Lake Tahoe
Heavy Backpacks May Damage Nerves, Muscles and Skeleton, Study Suggests
Feb. 21, 2013 — Trudging from place to place with heavy weights on our backs is an everyday reality, from schoolchildren toting textbooks in backpacks to firefighters and soldiers carrying occupational gear. Muscle and skeletal damage are very real concerns. Now Tel Aviv University researchers say that nerve damage, specifically to the nerves that travel through the neck and shoulders to animate our hands and fingers, is also a serious risk.
Prof. Amit Gefen of TAU's Department of Biomedical Engineering and Prof. Yoram Epstein of TAU's Sackler Faculty of Medicine, along with PhD student Amir Hadid and Dr. Nogah Shabshin of the Imaging Institute of the Assuta Medical Center, have determined that the pressure of heavy loads carried on the back have the potential to damage the soft tissues of the shoulder, causing microstructural damage to the nerves.
The result could be anything from simple irritation to diminished nerve capacity, ultimately limiting the muscles' ability to respond to the brain's signals, inhibiting movement of the hand and the dexterity of the fingers. In practice, this could impact functionality, reducing a worker's ability to operate machinery, compromise a soldiers' shooting response time, or limiting a child's writing or drawing capacity.
The research was published in the Journal of Applied Physiology and partially supported by a grant from TAU's Nicholas and Elizabeth Slezak Super Center for Cardiac Research and Biomedical Engineering.
Modeling impaired nerve function
Focusing their study on combat units in which soldiers must carry heavy backpacks, the researchers discovered that, in addition to complaining of discomfort or pain in their shoulders, soldiers also reported tickling sensations or numbness in the fingers.
Exploring this issue in a non-invasive manner, they used biomechanical analysis methods originally developed for investigating chronic wounds. The analyses show how mechanical loads, defined as the amount of force or deformation placed on a particular area of the body, were transferred beneath the skin to cause damage to tissue and internal organs.
Based on data collected by MRI, Profs. Gefen and Epstein developed anatomical computer models of the shoulders. These showed how pressure generated by the weight of a backpack load is distributed beneath the skin and transferred to the brachial plexus nerves. The models also account for mechanical properties, such as the stiffness of shoulder tissues and the location of blood vessels and nerves in the sensitive areas which are prone to damage.
Extensive mechanical loading was seen to have a high physiological impact. "The backpack load applies tension to these nerves," explains Prof. Gefen. He notes that the resulting damage "leads to a reduction in the conduction velocity — that is, the speed by which electrical signals are transferred through the nerves." With a delay or reduction in the amplitude or the intensity of signals, nerve communication cannot properly function, he says.
A danger to adults and children
These results apply to people from all walks of life, says Prof. Gefen. Many professions and leisure activities, such as hiking or travelling, involve carrying heavy equipment on the back. The researchers plan to extend this study in two directions: first, to study the effects of load on nerve conductivity, and second, to examine the impact of these heavy loads on a child's anatomy.
School bags are a major concern, he warns. It cannot be assumed that children's bodies react to shoulder stress in exactly the same way as adults. Differences in physiology could lead to different consequences, tolerance, and damage levels.Feb 25, 2013 at 7:21 pm #1958717
– -K.T.- –Participant
Hipbelts good then. Soldier sized loads, ugh. Nobody here should be even close to half of what they have to carry.Feb 25, 2013 at 7:54 pm #1958723
@cameronLocale: Idaho Falls
Soldiers get it bad in a number of ways
1. Those bullet proof vest are all on their shoulders. Often it looks like they are adding ammo to this load.
2. I've seen soldiers carrying rucksacks that were way too short for their torso length. The could just be "GI" sizing. I've also seen discussions where military packs were rated on whether or not you could tilt your head back enough to shoot from the prone position.
3. They run and jump off things with those heavy loads.
I'm not part of the military but apparently there has been somewhat of a debate over whether or not soldiers would fight better with less stuff, even if that meant going lighter on body armor.
Kids in school have all the weight on their shoulder and those bags can be HEAVY. No hipbelts or structural support and most of the book bags have less padding on them then a SUL pack.
I really doubt a hiker would have any problems with a properly fitted pack. Even a with a non-UL load.Feb 25, 2013 at 10:05 pm #1958758
@rexLocale: Central California Coast
Way back when, carrying 45-60 pound loads in traditional framed backpacks (REI, Trailwise), I had serious problems with numbness on the top surface of my thighs. Sometime the numbness would continue for days after a trip.
Completely forgot about that until this thread came up, because much lighter loads and internal frame packs with more flex solved that problem for me a long time ago.
The problems described in the article probably depend on body variations (size, fat, muscle, fitness, gender), pack design, weight, and field conditions.Feb 26, 2013 at 7:18 am #1958810
@carpenhLocale: St. Vrain River Valley
"The problems described in the article probably depend on body variations (size, fat, muscle, fitness, gender), pack design, weight, and field conditions."
Agreed. I'd like to read the original study. There's bound to be discrepancies.Feb 26, 2013 at 8:09 am #1958827
In my experience, all of my military gear performed much better than anything I can find in the civilian world. My bivy was actually 100% waterproof. My Goretex Jacket was bomber in the brush, never delaminated on me, ventilated well and kept me reasonably dry (of course I'd DX it every 2-3 years). My poncho was only used as a hooch shelter but with a few bungee cord and in conjunction with my bivy and USGI sleep system made for an awesome 4 season shelter.
That bomber performance comes with a massive weight penalty. The USGI sleep system is several pounds. The poncho is another 1.5 lbs.
Then add extra batteries for the RTO. A couple belts of ammo for the gun team. Extra mortar rounds for the mortar maggots. 72hrs of MREs. 1 – 1.5 gallons of water. Extra personal ammo. Other mission essential equipment. Etc, etc.
The Alice Pack technically has a hip belt but you never use it as it's not a safe practice on combat patrols and does not work when you are wearing an LCE which is loaded down with at least 6 full mags and whatever other. By the time everything is said and done, the ruck is >75lbs and all of that weight is carried on the shoulders.
Thank goodness that the military has learned from this and has gone to assault packs which are geared to keeping the load lighter (relatively speaking). I lost an inch of height due to my vulture infantry posture.
Needless to say I now embrace the UL experience and enjoy watching other vets make that transition as well.Feb 26, 2013 at 12:27 pm #1958942
@acrosomeLocale: Back in the Front Range
@ "1. Those bullet proof vest are all on their shoulders."
Nah- the IBA, IOTV, and more recent vests have a belly-band. I'll grant that it doesn't work nearly as well as a true hipbelt, though.
@ "I've also seen discussions where military packs were rated on whether or not you could tilt your head back enough to shoot from the prone position."
This is also a consideration with helmets. The old PASGT helmets would roll down over your face if you tried to shoot from prone, because the rear of the helmet was so low that it would hit your back. The ACH is better.Feb 27, 2013 at 6:25 am #1959176
The school backpacks issue is real and a total PITA. Many schools have eliminated lockers, partly out of hysteria over "contraband being stored" and partly due to real issues, and the end-result is that kids have to carry all their books, food and (2 days a week) their PE gear on their backs every day.
For middle-schoolers with several large books, it's common for backpacks to be 15lb or more. Yet, these packs often have only the most rudimentary of straps and the necessity of design/utility means it's gonna be shoulder-straps only.
One benefit: when I help set up a Scout with his Kelty and a total pack weight of 17 or 18lb for seven days out, they often say, "Mr. Basil, this feels lighter than my school pack!" The benefit being a glass-half-full kinda benefit.Feb 27, 2013 at 8:11 am #1959212
W I S N E R !Participant
"For middle-schoolers with several large books, it's common for backpacks to be 15lb or more…"
My son's (6th grade) backpack weighs, on average, 27 pounds. We've put it on the scale.
But it has helped with backpacking; he now thinks all the loads I have him carry are light.Feb 28, 2013 at 8:08 am #1959665
Ever ridden a bicycle for hours and you end up with a numb crotch and a lifeless peener? It's probably a blessing.
Anyway, real world weight—70 lbs to 80 lbs for backpacking—only causes me problems when the pack is not fitted right regarding torso length and hipbelt cant, etc etc and all the rest. Ever wear a 60 lb ALICE pack without the hipbelt? The hands swell up and you get a good neck headache.
My Mystery Ranch packs are designed to carry weight with comfort and so I don't have the problems mentioned in the study. What fails? Not my body but these bloody boots—Feb 28, 2013 at 8:11 am #1959667Feb 28, 2013 at 8:53 am #1959686
In the world of expedition trips without resupply.Feb 28, 2013 at 9:06 am #1959688
@skopeoLocale: British Columbia
>> My son's (6th grade) backpack weighs, on average, 27 pounds. We've put it on the scale. <<
I think this is a real concern. At age 18 my son had to have back surgery to repair a damaged disk that was attributed to him carrying heavy school backpacks without a waist belt. This is particularly bad when they are young and the damage accumulates over the years. He always insisted on carrying "all" of his books all of the time and I nagged him but couldn't get him to change. His surgeon told us that a young back shouldn't be carrying heavy loads of books without a really good waist belt.Feb 28, 2013 at 9:08 am #1959689Feb 28, 2013 at 9:22 am #1959699
Average base weight, lets say 16lbs.
Assuming one water refill a day, one must carry ~4 liters. 8lbs.
Food, assuming 1.5 ppd.
80-24 (full water + gear) = 56lbs left for food.
56/1.5ppd food= 37.3 days
Dang. nearly 40 days without resupply.Feb 28, 2013 at 9:31 am #1959703
@dwambaughLocale: Pacific Northwest
People hauling scientific, climbing or photo gear get some big loads. There are a lot of folk using UL techniques to help offset those other goodies.
The guys who did the Arctic 1000 started out with pack weights of about 59 pounds and they are some of the most experienced UL hikers out there, so hearing about 80 pound totals is little surprise. Nuts, but still not surprising.Feb 28, 2013 at 9:35 am #1959705
And they (Arctic 1000) had to wear their closed foam sleeping pads around their torsos while hiking to stay warm—not something I'd ever consider doing.
Here are some food weight quotes worth considering. Ray Jardine recommends 2.5 lbs of food per day on a thruhike.
WIKIPEDIA QUOTE ON UL BACKPACKING
"Ray Jardine suggest 2.5 lbs of food per day for thru hiking."
QUOTE FROM LAWTON "DISCO" GRINTER
"It took me the bulk of 10,000 miles of long-distance hiking to really grasp the concept that junk food and carrying less food to save overall pack weight works against you both in the short-term and the long run." From SectionHiker.com.Feb 28, 2013 at 9:50 am #1959713
"Dang. nearly 40 days without resupply."
Dang, Tipi is only getting 8 days out of 80 lbs.
@dale – I am aware of that but wanted to have Tipi clarify his 'real world backpacking' commentary. Last I checked, Ryan's Alaska Trip was to be for 600 miles with a 55 lb pack. Just curious as to how many miles Tipi is getting in 'real world' backpacking.
I still want to see a gear list… "My Dana Terraplane is obscenely heavy with about 80 pounds of food, books, camera, radio, sodas and all else."
Coke or Pepsi?Feb 28, 2013 at 9:53 am #1959715
So let me understand this, Tipi. "Real World" backpacking to you is Thru hiking. Have you ever thru hiked with your 80 lb load?Feb 28, 2013 at 10:46 am #1959734
Canards on a tangent… :)
The "nerve damage" issue is one many kids face, with heavy backpacks in the "bookbag" or "daypack" style and a significant period of time with them on, either walking or riding to school. Our son couldn't ride his bike home from the day in 6th grade when he got all his books, because his backpack was so heavy he was unstable as he struggled to haul it…
Aside from book bags, I have certainly heard complaints about shoulder pain from youth I backpack with. In some cases, it's clearly an issue with too much weight and a pack that doesn't fit well. With others' kids, it's not always so simple to spend our way into UL or the right "kind of pack", but we do try to reduce those loads in volume and mass.
Many times, with either adults or youth, the matter is really that the pack is poorly fitted. With a torso that's too short, the hiker must choose between too much weight on the shoulders or a hip belt cinched on the belly. A pack that's super light might have super-thin or flimsy shoulder straps that dig into the untrained [by pain! :)] shoulder, and a pack with big, old hardened pads might bruise the collar bones over the course of a day. A pack that's too long in the torso might result in the rig floating high off the shoulders and then, of course, either flopping backward or inciting the hunched-forward posture that often suggests one is fighting with the backpack.
Those well-fitted and designed packs, like we see described/claimed about Dan McHale and Dick Kelty's products [ :) ], sure pay off and resolve these issues for many of us. One thing for sure: lighter loads have less impact and effect whether or not there are problems with the pack.Feb 28, 2013 at 5:26 pm #1959864
Erik says it right—
"Those well-fitted and designed packs, like we see described/claimed about Dan McHale and Dick Kelty's products [ :) ], sure pay off and resolve these issues for many of us."
As I was saying about my Mystery Ranch pack. Designed to haul weight with attention paid to physical comfort.
On my last 18 day trip my food load was almost identical to Jardine's recommendation of 2.5 lbs a day—45 lbs.Feb 28, 2013 at 8:25 pm #1959953
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