Inter-individual variability in load carriage economy and comparisons between different load conditions

Abstract

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Evaluating the human capacity of carrying loads without costs: A scoping review of the Free‐Ride phenomenon

“…Nonetheless, and remarkably, despite the characteristics related to load size, speed, and expertise that the 8 studies reporting the Free-Ride have in common, the analysis of the 45 studies shows that none of these aspects influence the probability to find Free-Ride or not (p value >.05) (Table 1). Either way, even when our main results do not support a general Free-Ride capacity, many authors (Abe et al, 2008b;Falola et al, 2000;Hudson et al, 2020Hudson et al, , 2021Kramer, 2003;Pal et al, 2014;Soule et al, 1978;Vickery-Howe et al, 2021;Watson et al, 2008) recognize that some of the participants in similar experiments were able to carry loads very economically under certain conditions. Therefore, many researchers highlight the high individual variability, affecting the costs of both loaded and unloaded trials (de Mendonça & Pereira, 2008;Heglund et al, 1995;Hudson et al, 2020;Kramer, 2010;Rue & Kramer, 2017;Vidal-Cordasco et al, 2021), were some individuals decrease their locomotion costs for some burdened trials, whereas other subjects increase their costs of locomotion when the load is increased.…”

“…Thus, experience, especially at a high level of training, maybe also an important factor to consider for future experimental designs. However, many others considering also highly experienced carriers disagree with this assumption (Grenier et al, 2012; Hudson et al, 2020; Lloyd et al, 2011; Lloyd, Parr, Davies, & Cooke, 2010; Pal et al, 2014), and according to this review, the possibility to find a Free‐Ride capacity in the literature is not related with the interaction between the experience of the carriers and the load position, neither between the experience of the carriers and the load size (Table S2).…”

“…Load transport is necessary for many daily labors, in hunter‐gatherer and farming societies (Bastien, Schepens, et al, 2005; Hilton & Greaves, 2003; Hurtado et al, 1985; Malville, 1999) and in urban populations (Attwells et al, 2006; Bouterse & Wall‐Scheffler, 2018; Godhe et al, 2020; Hudson et al, 2020). In fact, humans devote most of their energy expenditure to locomotion during physical activities (Passmore & Durnin, 1955), with load carrying being a crucial behavior that influences the costs of walking and, in consequence, human daily energy budgets (Kramer, 2003; Wall‐Scheffler & Myers, 2013).…”

“…Following previous publications, in order to test the Free‐Ride phenomenon, it is important to consider existing investigations comparing the cost of transporting a load with the cost of unloaded locomotion (Hudson et al, 2017; Lloyd, Hind, Parr, Davies, & Cooke, 2010); as well as papers including both heavy (considered here as >10 kg or >15% of the participant's body mass) and light to moderate burdens (≤10 kg or ≤15% of the participant's body mass), because some authors support that the Free‐Ride capacity will not be found carrying heavy loads (Watson et al, 2008); but see Maloiy et al (1986) who suggested that above the 20% of body mass, the energy expenditure increases proportionally (e.g., a 30% load increases energy consumption by a 10%). Other aspects, such as the experience of the participants as carriers (Maloiy et al, 1986; but see Hudson et al, 2020) and the speed selected for the experimental tests (Bastien, Willems, et al, 2005) should also be taken into account to address if other researchers find the Free‐Ride capacity. These considerations are essential to designing future experimental tests.…”

Energy cost of walking and body composition changes during a 9-month multidisciplinary weight reduction program and 4-month follow-up in adolescents with obesity

“…The extra weight or mass added to the chest wall, as in obesity condition, causes a compression of the thorax, thus decreasing respiratory compliance and lung volumes (Wang and Cerny 2004). As previously observed in healthy and lean subjects, a load on the D r a f t trunk between 15-20% of body weight, as observed in obesity (Hong et al 2008;Hudson et al 2020), causes chest wall restriction with a concomitant increase in work of breathing and Cw (Faghy et al 2016;Faghy and Brown 2014;Phillips et al 2016). Therefore, previous studies showed that a 12-week diet and physical activity program, induced BM loss and reduction of trunk FM, which significantly enhanced breathing mechanics in men and women with obesity (Babb et al 2011;Bhammar et al 2016).…”