# Effects of a Wearable Carriage Aid on Whole-Body Physiological Measures and Balance
## 1 Introduction  
Manual material handling (MMH) tasks are still frequent in many occupational sectors despite developments made in production technologies [1, 2]. Potential motives to keep these tasks manual include benefiting from the worker skill, experience, and movement flexibility [3]. Interventions targeting physically demanding tasks can be broadly classified as administrative or engineering. A frequently used engineering approach is to automate targeted tasks. However, this solution can be practically impossible or requires unreasonably high capital investments. Wearable assistive devices are increasingly emerging for occupational use and may be a suitable alternative or aid to existing intervention methods [4]. This is because using these devices can require relatively minor changes to a present workplace and can be more cost-efficient.  
However, the described wearable assistive devices (also known as exoskeletons) have been mostly assessed for military, rehabilitation, or medical purposes as an aid for patients who are injured, weak, or disabled [5, 6]. A study showed that these devices can considerably reduce physical demands for occupational use [7]. However, wearing these devices can also have unintended influences such as raising physical demands on other body regions while reducing demands on targeted body parts. For example, wearing a passive exoskeleton reduced back and leg demands but increased chest discomfort in a simulated assembly task that involved a truck [8].  
Load carriage is a common MMH task and is considered a combination of lifting and pulling or pushing tasks [9]. Load carriage was considered as one of the three most frequently performed MMH tasks in the U.S. [9]. For the U.S. Army soldiers, carrying and lifting tasks were specified as the most common physically demanding tasks [10]. [PERSON] and [PERSON] [11] showed evidence that carryingtasks can lead to lower back and shoulder pain. To highlight the economic influences of these injuries, the annual direct costs for lower back and shoulder injuries were estimated to be at least $50 billion [12] and $7 billion [13], respectively.  
Generally, carriage wearable aids redistribute the load over the wearer's body to reduce demands on the lower back and shoulder regions [14]. A few studies have specifically investigated the effectiveness of these devices in reducing carrying task physical demands. [PERSON] and [PERSON] [15] found that a simple wearable carriage aid can reduce lumbosacral moments after load carriage tasks. Investigating these wearable devices is commonly completed using regional physical demand measures. While these measures can provide specific effects, knowledge on the global (or whole-body) physical demand measures might be limited. Evaluating the whole-body effects is critical as per the described common and potential unintended consequences of wearing these devices. Therefore, this study examined the influence of a wearable carriage aid on whole-body physiological measures (normalized oxygen consumption, respiratory rate, minute ventilation, and heart rate) while considering the potential moderating influences of carried load mass. Additionally, this study assessed the effect of wearing this device on perceived postural balance. The proposed aid was examined earlier using regional measures and it showed potential to reduce shoulder and arm demands while slightly increasing lower back demands (cf., [14]). To completely understand the effectiveness of the developed aid, this study was conducted as per the whole-body measure. We hypothesized that the aid would improve all physiological measures and perceived postural balance regardless of the carried load mass.