Musculoskeletal injuries are commonly reported in workers employed in labor-intensive agricultural-type tasks. A novel method of determining joint angles, joint torques, and contact forces, using three-dimensional motion capture and musculoskeletal modeling, was applied to the movements of a sample of workers, engaged in the horticultural task of digging, to determine if objective biomechanical data could be correlated with a subjective visual assessment to predict risk of injury. The joint angle time histories of horticulturists were calculated from the motion capture data, and this was used to articulate a musculoskeletal model of the subjects. The joint torques were calculated using inverse dynamics methods from which the individual muscle loads were established using a cost function minimization approach. Finally, the joint contact forces were calculated including the muscle forces. The motion capture data of digging trials were observed by a team of horticulturists and physiotherapists who categorized each of the observed trials according to form, efficiency, and risk of injury. Trials demonstrating techniques which were more likely to yield injuries were identified as “examples of bad technique”; those judged to be less likely to yield injuries were categorized as “examples of good technique.” It was found that the joint torques and contact forces and their variability were lower in the trial which was identified as good technique, and consistently higher in the examples of bad technique. The results of the study suggest that measurement of joint angles, joint torques, joint contact forces, and forces in the muscles could serve as a valuable tool to develop training programs for horticultural workers engaged in certain high intensity tasks, such as digging, to effectively improve efficiency and reduce incidence of injury. It may also be possible to modify horticulture-related equipment to minimize the internal loads within the body to reduce the risk to health and, therefore, extend active participation in horticulture.
James Shippen, Paul Alexander, and Barbara May
Servet Kefi, Paul E. Read, Alexander Pavlista, and Stephen D. Kachman
To determine the influence of gibberellic acid (GA3) and 6-furfuryl aminopurine (kinetin) concentrations alone and in combinations on in vitro tuberization of potato, nine treatments consisting of combinations of gibberellic acid and kinetin at three levels of concentration (0, 2, and 5 mg·liter–1) were included in Murashige and Skoog medium supplemented with 6% sucrose. Four single nodes of in vitro plantlets from Solanum tuberosum L. cultivar Atlantic were placed into each magenta box. All magenta boxes were arranged in a randomized complete box design with five replications and cultured under a short photoperiod condition (8 h light/16 h dark). Gibberellic acid strongly inhibited tuberization when used alone or with kinetin, whereas kinetin induced tuberization at both 2 and 5 mg·liter–1. Although tuberization was initiated in the absence of kinetin because of the high concentration of sucrose and short photoperiod, the presence of kinetin accelerated the in vitro tuberization process of potato.
Servet Kefi, Paul E. Read, Alexander D. Pavlista, and Stephen D. Kachman
The role of sucrose alone and in combination with different cytokinin-like compounds on the microtuberization of potato, Solanum tuberosum `Atlantic', was investigated. Single nodal segments were placed in Magenta boxes containing Murashige & Skoog medium supplemented with one of 15 treatments in a 3 × 5 factorial. Treatment factors were sucrose at 3%, 6%, or 9%, and cytokinin-like compounds at five levels [cytokinin-free; 2 mg kinetin/L; 0.1 mg thidiazuron (TDZ)/L; 1.0 mg AC 243,654/L; 0.1 mg AC 239,604/L]. Except in a few cases in kinetin and TDZ treatments, nearly all cytokinin treatments failed to induce tuberization at the 3% sucrose, noninductive level. However, all cytokinin treatments induced tuberization in the presence of 6% sucrose. By raising the sucrose level from 6% to 9%, more and larger microtubers were obtained in the cytokinin-free medium. At the 9% sucrose level, even though more tubers per box were produced by TDZ and AC 243,654 treatments, less total fresh weight of tubers per box resulted from kinetin, TDZ and AC 243,654 treatments because tubers formed were smaller. Higher sucrose concentrations (9%) favored tuberization in the cytokinin-free medium, whereas 6% sucrose was optimum for the medium containing cytokinins. Sucrose might produce a strong tuberization signal that might either change endogenous hormone levels affecting tuberization or activate a number of genes coding tuber proteins and enzymes related to starch synthesis.