A backpack is a carrying device designed to distribute a load across the back using shoulder straps. When worn correctly, it helps maintain an upright posture and minimizes mechanical strain on the spine. Improper use can disrupt natural alignment and increase the risk of discomfort or injury. Understanding how to select, adjust, and load a pack is fundamental to managing carried weight effectively.
Selecting the Right Backpack Size and Style
Choosing a backpack that fits the wearer’s body is the first step, determined by torso length, not overall height. To find the correct measurement, identify the bony protrusion at the base of the neck (C7 vertebra) and the top of the hip bones (iliac crest). The distance between these two points defines the torso length, which should correspond to the backpack’s back panel size for an optimal fit.
The backpack should possess features that help manage the load efficiently. Padded shoulder straps provide comfort, but they should not bear the majority of the weight. A well-designed backpack includes both a hip belt and a sternum (chest) strap. The padded hip belt transfers the load to the pelvis and legs, which handle significantly more weight than the shoulders. The sternum strap secures the shoulder straps and prevents the pack from shifting side-to-side, aiding stability during movement.
Step-by-Step Adjustment of Straps
The process for achieving a proper fit is sequential and begins with loosening all straps before putting the pack on. Once the backpack is on, the first adjustment is the hip belt. The hip belt should be centered over the iliac crest (the bony shelf of the hips) and tightened firmly to transfer the bulk of the load (ideally 70 to 80 percent of the total weight) away from the shoulders.
With the hip belt secured, the shoulder straps are adjusted next, pulling them down and back until they are snug against the shoulders. The shoulder straps should gently hug the shoulders but not be so tight that they pull the pack away from the hips or cause discomfort. They function primarily to stabilize the load and keep the top of the pack close to the body, not to carry the weight.
Finally, the sternum strap is fastened across the chest, typically an inch or two below the collarbones. This strap should be adjusted just enough to prevent the shoulder straps from sliding outward. The sternum strap works to pull the shoulder straps inward, which increases the stability of the load and allows for unrestricted arm movement. When all straps are adjusted in this sequence, the pack should feel like a secure extension of the body.
Optimal Loading and Weight Distribution
The placement of contents inside the backpack is nearly as important as the fit of the straps for maintaining balance and reducing strain. The weight of the entire loaded pack should not exceed 10 to 15 percent of the wearer’s body weight for daily use, or up to 20 percent for heavier loads carried during activities like backpacking. Exceeding this range increases the likelihood of postural changes and muscle fatigue.
The heaviest items should be positioned closest to the back and centered between the shoulder blades. Placing dense objects near the center of the back aligns the pack’s center of gravity with the wearer’s, preventing the pack from pulling backward. This arrangement reduces the force required by the back muscles to maintain an upright posture. Lighter items, such as clothing or sleeping bags, should be placed further away from the back, often toward the bottom or the outside compartments.
Recognizing Signs of Improper Wear
The body provides several immediate and long-term signals when a backpack is not worn correctly or is overloaded. A common postural sign is a tendency to lean forward excessively to counterbalance the weight of the pack, which strains the lower back muscles. Another indication of improper fit or excessive load is the presence of persistent back, neck, or shoulder pain that worsens while wearing the pack.
Tight or misplaced shoulder straps can compress the nerves that pass through the shoulder area, leading to symptoms like tingling or numbness in the arms or hands. Red marks or chafing on the shoulders or hips also signal that the straps are digging into the skin and creating unhealthy pressure points. If these symptoms appear, the load needs to be reduced, the contents rearranged, or the straps readjusted to ensure weight is transferred appropriately to the hip belt.