Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, P.O. Box 5626, SE-114 86 Stockholm, Sweden.
Mil Med. 2020 Aug 14;185(7-8):e1168-e1174. doi: 10.1093/milmed/usaa050.
The ability to carry heavy loads is an important and necessary task during numerous outdoor activities and especially in military operations. The aim of this study was to investigate factors associated with load-carrying ability in men and women with and without extensive load-carrying experience.
The energy expenditure during carrying no load, 20, 35, and 50 kg at 2 walking speeds, 3 and 5 km h-1, was studied in 36 healthy participants, 19 men (30 ± 6 years, 82.5 ± 7.0 kg) and 17 women (29 ± 6 years, 66.1 ± 8.9 kg), experienced (>5 years) in carrying heavy loads (n = 16, 8 women) or with minor or no such experience (n = 20, 9 women). A standard backpack filled with weights to according carry load was used during the walks. Anthropometric data, leg muscle strength, as well as trunk muscle endurance and muscle fiber distribution of the thigh, were also obtained. Extra Load Index (ELI)-the oxygen uptake (VO2) during total load over unloaded walking-was used as a proxy for load-carrying ability at 20, 35, and 50 kg (ELI20, ELI35, and ELI50, respectively). In addition to analyzing factors of importance for the ELI values, we also conducted mediator analyses using sex and long-term carrying experience as causal variables for ELI as the outcome value. The study was approved by the Regional Ethics Committee in Stockholm, Sweden.
For the lowest load (20 kg), ELI20, was correlated with body mass but no other factors. Walking with 35 and 50 kg load at 5 km h-1 body mass, body height, leg muscle strength, and absolute VO2max were correlated, while relative VO2max, trunk muscle endurance, and leg muscle fiber distribution were not correlated to ELI35 and ELI50.ELI50 at 5 km h-1 differed between the sexes. This difference was only mediated by the difference in body mass. Neither muscle fiber distribution, leg muscle strength, trunk muscle endurance, and body height nor did absolute or relative VO2max explain the difference.Participants with long-term experience of heavy load carrying had significant lower ELI20 and ELI50 values than those with minor or no experience, but none of the above studied factors could explain this difference.
The study showed that body mass, without sex differences, and experience of carrying heavy loads are the dominant factors for the ability to carry heavy loads. Even though the effect of experience alludes to the need for extensive carrying training, no causality can be proven. Load carry training intervention studies is suggested for future investigations.
在许多户外活动中，尤其是在军事行动中，携带重物的能力是一项重要且必要的任务。本研究旨在探讨有和没有负重经验的男性和女性在负重能力方面相关的因素。
36 名健康参与者（19 名男性，30±6 岁，82.5±7.0kg；17 名女性，29±6 岁，66.1±8.9kg）在 2 种步行速度（3 和 5km/h）下分别进行无负重、20、35 和 50kg 负重行走时的能量消耗研究。其中 16 名参与者（8 名女性）有携带重物（＞5 年）的经验，20 名参与者（9 名女性）经验较少或没有此类经验。在行走过程中，参与者使用装满重物的标准背包。还获得了人体测量数据、腿部肌肉力量以及躯干肌肉耐力和大腿肌肉纤维分布。总负重时的耗氧量（VO2）与无负重行走时的耗氧量之比（Extra Load Index，ELI），作为 20、35 和 50kg 负重能力的替代指标（分别为 ELI20、ELI35 和 ELI50）。除了分析对 ELI 值重要的因素外，我们还使用性别和长期携带经验作为因果变量进行中介分析，以 ELI 作为因变量。该研究得到了瑞典斯德哥尔摩地区伦理委员会的批准。
对于最低负荷（20kg），ELI20 与体重相关，但与其他因素无关。以 5km/h 速度携带 35 和 50kg 时，体重、身高、腿部肌肉力量和绝对 VO2max 与 ELI35 和 ELI50 相关，而相对 VO2max、躯干肌肉耐力和腿部肌肉纤维分布与 ELI35 和 ELI50 不相关。5km/h 时的 ELI50 在性别之间存在差异。这种差异仅由体重的差异介导。肌肉纤维分布、腿部肌肉力量、躯干肌肉耐力和身高，以及绝对或相对 VO2max 均无法解释这种差异。有长期负重经验的参与者的 ELI20 和 ELI50 值明显低于经验较少或没有经验的参与者，但上述研究因素均无法解释这种差异。
本研究表明，体重（无性别差异）和携带重物的经验是携带重物能力的主要因素。尽管经验的影响暗示需要进行广泛的携带训练，但不能证明存在因果关系。建议进行携带训练干预研究，以进一步研究。
