The impact of pack load and footwear on lower limb injuries
An in-depth research article

The following synopsis is from ongoing research being conducted and kindly shared with Crossfire Australia. The author has asked not to be identified at this stage as yet as the research remains ongoing.

I have done work regarding injuries and pack load and also the impact of footwear on lower limb injuries. As far as shoulder injuries are concerned we assessed male and female service personnel to identify the risk of a shoulder injury as the pack they were carrying at the time was believed to be the cause of shoulder injuries. We found 43% of males and 38% of females were at risk of injury due to lack of appropriate upper body conditioning before commencing with training. Our research also revealed the type of pack being used may be a contributing factor to shoulder injuries. The pack being used at the time made use of an internal frame, and when worn without the belt a force in 3 planes is produced – the expected drag down, a rearwards force as the pack levers off the lower back, and also a distracting force or rotational component (the strap attachments are more central on a soft frame). The difference with a framed pack is that it doesn’t lever off the lower back and straps are usually held wider on a fixed frame

Shoulder straps of a pack usually cause a traction injury of the C5 and C6 nerve roots of the upper brachial plexus. This results in the entrapment of the long thoracic nerve causing numbness, paralysis, cramping and pain in the shoulder girdle, elbow flexors and wrist extensors. There are also numerous other factors which may cause shoulder injury to soldiers when carrying packs; these include the amount of load carried, duration of pack carriage, physical conditioning of the soldier and different pack types (badly designed packs not suited for military use). Studies have shown that soldiers carrying packs without a frame had higher incidences of brachial plexus palsy. Bessen et al (1987) reported an injury rate 7.4 times higher for soldiers wearing a pack without a frame compared to those using a frame.

A heavy load transferred through the shoulder strap of a pack to the underlying soft tissue may affect the neural performance of the upper limb due to trapped nerves or a reduction in blood supply. Load/pack carriage systems address this by transferring loads to the hip area through external rigid frames and waist belts, therefore the use of an external frame and hip belt will reduce the incidence of rucksack palsy by reducing pressure on the shoulders. Research has shown that framed packs with hip belts reduce the neuromuscular activation of the trapezius muscle whereas a frameless backpack increases activation of the trapezius muscle, subsequently, a framed pack will reduce the incidence of rucksack palsy.

The wearing of a chest strap also appears to be beneficial for reducing brachial plexus strains by positioning the shoulder straps in a more medial aspect. The more lateral the placing of the shoulder strap, the less protection the clavicle can provide to the subclavian artery and the brachial plexus.

This, in combination with inadequate upper body strength and stability is a significant risk for shoulder injuries.

Our results suggest a frameless pack being carried by cadets with unconditioned, functionally asymmetrical upper bodies are the causes of the high number of shoulder injuries. As a result of this, the pack was replaced with a pack having an external frame, this reduced the injury rate significantly.

As far as lower limb injuries are concerned we have found that continuous wearing of military boots, particularly boots with stiff upper shafts and thick inflexible soles are a cause of ankle and lower limb injuries. We measured the range of movement, electromyography, lower limb strength, balance and stability on military recruits before they were issued with military boots and re-tested them 12 months after being in the military and having worn military boots. This study documents the adaptations due to wearing the military boot for just one year.

It significantly reduces the strength and endurance of the gastrocnemius muscles in plantarflexion in addition to a reduced range of inversion and eversion motion.

• In tandem, these changes cause a weakening of the ankle joint and increased reliance on the boot to support the ankle.
• The stiff and high shaft of the military boot restricts movement and over time decreases normal range of motion in all planes of ankle motion so that the natural structures of the foot become weakened. This leads to the reliance of the footwear to support the foot and ankle.
• When the boot is not worn there is no external support of the joint which would be a major contributor to injuries in activities of sport and running when wearing normal flexible and soft training shoes.
• The ability of the muscles to respond quickly is decreasing.
• The balance is significantly compromised, with a larger movement of the centre of pressure in the medial-lateral direction.
• Medial and Lateral Gastrocnemius becoming less active.
• It appears Tibialis Anterior remains or is more active.
• The lack of medial-lateral muscle engagement likely contributes to the high rates of inversion injuries.
• Tibialis Anterior seems to be overworking to maintain balance – can lead to medial tibial stress syndrome (MTSS) (shin splints).
• The boot is making the muscles crossing the ankle joint ‘lazy’.

After 35 years of building outstanding backpacks for both the civilian and military communities. The Crossfire brains trust has designed what we humbly believe one the very best purpose designed military packs on the market

The DG-16 is designed with one thing in mind, which is to allow you to be functional and not be completely fatigued prior to the task.  The DG-16 will not compress vertebrae, crush nerve groups or displace discs. Fit for the fight.

We had the mild hope that some of the firms copying our designs might actually achieve a half decent result. But they have copied the look, not the quality and function. So instead of retiring we pushed the button on tooling for a very big step up in military packs.

The DG16 embodies everything we have learnt in three decades. Materials science, ergonomics, systems integration, all with end users feedback. This pack has been engineered from first principles. There is nothing else like it, anywhere.

DG16 Polymer Frame

The trick is to source aerospace level resin and invest in vastly expensive high-pressure injection moulds. Then, use finite element analysis to tune the frame to flex at the same rate as the human back. Too little flex, like metal frames, forces the hips and shoulders to fight with every stride. Fatiguing. Overflexing forces the shoulders to fight angular momentum as the load swings wide with each step. Waste of energy.

The DG16 flexes just right, hips and shoulders move freely, the stride is longer and less exhausting. Active ventilation keeps things cool, reminds you of ALICE? The window shape snugs over a body armour plate. The harness system can be quickly set at different levels to accommodate different torso lengths.

DG16 Shoulder Harness

We don’t slap some fabric over a piece of foam and call it a shoulder strap. We would call that rope. The harness arms are laminated from multiple layers of specialty, expensive materials. Plastic plate reinforcements distribute heavy loads, memory foams to customise to the user. Shoulder straps are shaped and tapered to work over CBA and smoothly transfer load away from the brachial plexus nerve group. The whole shoulder harness yoke assembly can be quickly extended up or retracted down with three height settings built into the webbing attachments.

Shoulder Release

It is our belief that any pack which uses a 25mm plastic side release buckle as a load element is not fit for service. Such a culpable object should be recalled and destroyed before it injures the user. Such buckles were never intended for heavy, load-bearing use. They can release or break inadvertently, slewing the fully loaded pack and wrenching the spine. The DG16 shoulder harness uses reliable, strong yet easy-to-release-under-load military-proven buckles. Because we really do care.

Hip Belt System

Choose the set up according to personal preference and type of rig. There are three plug-in adjustment levels for the padded components so they can be tuned to back length, set high to clear a belt rig, or set low to hip load. Or remove hip fins and use lumbar loading.

DG-16 Pack Bag

User designed, just brilliant.
Walk through the gallery photos or read on down the comprehensive list of design features follows, and be amazed just how diligent we are in providing the features required by those who put themselves in harms way.

Learning from the past is important as they say otherwise you’ll repeat the same mistakes. Can we learn from old traditional designs, or techniques and apply them to modern design? Are all earlier design’s and technology inferior?

External frame backpacks are interesting not only of their more versatile modularity but also because the structural component of the pack is clearly visible and offers a great opportunity to explore structural innovation. New technology and new materials open new opportunities. The civilian backcountry and mountaineering community have generally been at the cutting edge of pack innovation with the mantra “every gram counts”.

From the first recognised commercially made external frame in 1952 when Asher “Dick” Kelty started the Kelty brand from their garage in Glendale, California. One of the biggest innovators in backpack design, Kelty was not only one of the first to produce and market external-frame backpacks specifically for civilian use, but Kelty is also considered to be the inventor of the rectangular aluminium framed backpack, the hip belt, using nylon, adding zippers to the pack pockets and the padded shoulder straps Jump forward a few years and the emergence of The ALICE (All-Purpose Lightweight Individual Carrying Equipment) load-bearing system, was adopted as United States Army on 17 January 1973 to replace the M-1956 Load-Carrying Equipment (LCE). A simple pack that took-pretty much anything you threw at it. Its critical vulnerability being the aluminium frame and the dreaded rivet pop.

Since then there have been variants of the ALICE Frame that have come and gone in plastics, metal, polymers but all still largely drawing on the tech and innovation of the original 1973 adopted system. Jump forward to 1985 and our own Ian Malley’s WE SAS Pack design completely  out of the left field but was widely accepted and adopted across both SOF and big army.

One would think that a country’s soldiers would be afforded the very best equipment that could be provided. Up until 2001, Australia like the US and a number of our close allies received the very best training in the world, some of the most advanced weaponry, but the worst large field packs. In the field, the soldier’s packs are their home and everything for their comfort, survival, and efficiency must be carried on their backs. Throughout World War 1 and World War 2, the packs carried by the soldiers were nothing more than bags with straps sewn into them. They were made from cotton, they became saturated in the rain and their carrying capacity was limited. The evolution of the army’s backpacks was slow and in the early 1980s, the ALICE pack was developed by the US.

Although an improvement over the preceding models, the full packs on long marches became uncomfortable and chafing not to mentioned the dreaded popped rivet after a not so soft jump. Uncomfortable, broken soldiers are inefficient soldiers and being miserable is a good road to failure. Finding a Better Solution after September 11, 2001, Australia as with most modern armies started the Rapid Fielding Initiative to equip their warfighters with the best state of the art equipment to enhance their mobility, lethality, and survivability in the fields of Afghanistan and Iraq.

As part of this initiative, the MOLLE pack was developed. M.O.L.L.E. stands for ‘modular lightweight load-carrying equipment’. It is constructed of 1000 Denier Cordura, it has an external pack frame, a shoulder strap assembly, waist belt, and a quick release. The main rucksack is 3000 cu in. and houses the Gortex sleeping system, night vision goggles, GPS, personal items and body armor. There are pouches for grenades, a hydration bladder that eliminates canteens and there is a separate assault pack to carry extra ammunition. The MOLLE pack has seen extensive service by all nations involved in Iraq and Afghanistan since 2001. However, soldiers in the field voiced criticisms of certain aspects of the MOLLE design. For example, the external plastic frame of the main pack was prone to breakdown under field conditions and a number of lower back injuries were attributed to the ball-and-socket mechanism between the frame and waist-belt. In addition, the straps were too short to accommodate body armor.

Since 2001 the search for the optimal field pack has continued. The Australian model seems to have largely followed for better or worse the US model of bigger, wider, more pouches for the field pack large. The experience of the civilian mountaineering world seems to have been largely excluded or ignored. The revolution in the civilian world in both type of materials used for both frames and bag and the frame sizing has very much left defense in its shadow. The days of one size fits all and the thought process that a pack has been 1000D to be robust enough is very much gone the way of the dodo. The Crossfire DG family of packs begin to represent the innovation of the civilian mountaineering into the military environment.