Metabolic response to repetitive lifting tasks: predetermined vs. self-selected pace
Sevene, TG, DeBeliso, M, Harris, C, Berning, JM, Climstein, M & Adams, KJ 2013, 'Metabolic response to repetitive lifting tasks: predetermined vs. self-selected pace', International Journal of Science and Engineering Investigations, vol. 2, no. 16, pp. 68-71.
Abstract- Understanding the metabolic demands of repetitive lifting tasks with different pacing strategies may help increase productivity and prevent injuries. The purpose of this study was to determine the metabolic response of repetitive lifting tasks performed with different loads and different pacing strategies. Metabolic parameters were recorded as eight male participants (age = 24 ± 6 yr, height = 173 ± 9 cm, weight = 83 ± 23 kg) participated in predetermined pace (PP) and selfselected pace (SP) weight transfer tasks. The tasks required participants to transfer two 11.4, 15.9, and 20.5 kg weight plates individually back and forth a distance of 195.6 cm horizontally and 115.6 cm vertically (lift from 40.6 cm to 156.2 cm high). Task PP required participants to transfer the 6 weight plates each minute for 10 min (i.e., 60 total transfers); task SP required participants to make the 60 transfers in 10 min or less at a self-selected pace. Statistical analyses were made using both steady state and complete task metabolic data. Results were as follows: significant (p = 0.000) differences were observed in VO2 based on pacing strategy (PP or SP) during the transfer of 11.4 kg (PP = 13.0 ± 2.3 vs. SP = 17.8 ± 3.7 ml.kg-1.min-1 ), 15.9 kg (PP = 14.5 ± 2.9 vs. SP = 19.3 ± 4.9 ml.kg-1.min-1 ), and 20.5 kg weights (PP = 17.5 ± 4.2 vs. SP = 21.7 ± 5.3 ml.kg-1.min-1 ); mean VO2 and HR were significantly (p = 0.000) higher during SP (19.6 ± 4.9 ml.kg-1.min-1 , 123 ± 13 bpm) than during PP (15.0 ± 3.7 ml.kg-1.min-1 , 109 ± 12 bpm); mean time (min) to completion was significantly faster during SP: 11.4 kg (6.5 ± 1.0), 15.9 kg (6.9 ± 1.0), and 20.5 kg (7.6 ± 1.0); regardless of pacing strategy, oxygen cost (VO2) was significantly higher (p < 0.05) as weight transferred increased; and time to complete the SP transfer task increased as weight increased; also, there was no significant difference (p < 0.05) in total (i.e., sum of the three work bouts) energy expenditure between SP (169.0 ± 20.0 kcal) and PP (173.0 ± 17.7 kcal). In conclusion: 1) when self-selecting pace, mean VO2 and HR were significantly higher than during predetermined pace at all workloads; 2) metabolic costs increased with increasing workload; 3) task completion was always quicker when pace was self-selected, but total energy expenditure was similar.