Scott MacKinnon

Reliability of electromyographic and force measures during prone isometric back extension in subjects with and without low back pain

Maximal voluntary isometric activations (MVIA) are frequently used as inputs for models attempting to predict muscle force and as normalization values in studies assessing muscle function. However, pain may adversely affect maximal muscle activation. The purpose of this study was to assess reliability of MVIA force and electromyographic (EMG) activity during prone isometric back extension in subjects with and without low back pain (LBP). A novel sub-maximal method using the percentages of the estimated mass of the head-arms-trunk (HAT) segment was also investigated. Repeated measures on 20 male volunteers divided into an LBP (n=10) and a control group (n=10) were made on 4 occasions. Force and EMG activity were recorded bilaterally from upper lumbar erector spinae (ULES), lower lumbar erector spinae (LLES), and biceps femoris (BF). Subjects exerted a maximal extension effort against a harness assembly that was attached to a force transducer. Submaximal exertions were also performed with an additional resistance of 100%, 110%, 120%, 130%, 140%, 150%, 160%, and 170% of HAT. Mean MVIA forces were significantly (p<or=0.05) lower in LBP vs. control. Intraclass correlation coefficients (ICC) for MVIA force, right and left ULES, and LLES EMG indicated high reliability in controls (R>0.90), but were significantly less in LBP (R=0.36-0.80). EMG of BF demonstrated excellent reliability across both groups (R>0.90). The resistance at 100% HAT demonstrated the highest reliability for LBP patients, whereas higher percentages of HAT showed either similar or higher reliability for controls. Force output and back EMG activity are less reliable with LBP individuals and should be taken into consideration when testing.

The energetics of walking on sand and grass at various speeds

This study investigated the energetics of walking on sand and grass. Fourteen adult males, participated in the study. Participants had a mean age of 34.6 years old, 72.6 kg in mass and 172.5 cm in stature, who walked at 3, 4, 5, 6 and 7 km per h on sand and grass surfaces. Physiological measures included heart rate, O2 uptake, CO2 exhalation, ventilation and relative O2 uptake using a MetaMax Ergospirometer. Speed was controlled in a methodology similar to the ‘Multistage 20-m Shuttle Run Test’. Data were collected during physiological steady rate at each determined speed. A minimum of 2 h rest was enforced between randomized conditions. Results indicate that there was a significant increase (p < 0.01) in all measured physiological indices indicative of energy expenditure when walking on sand compared to grass at 3–7 km per h, with the greatest disparity between the surfaces (ratio = 1.63) in relative O2 consumption at 5 km per h.

Interactive simulation for training offshore workers

This paper presents AVERT, a first-person simulator for general offshore workers that exposes them to a virtual environment similar to actual offshore sites and facilitates training in and assessment of spatial awareness, alarm recognition, and emergency response procedures. We follow the technical introduction with a case study showing the efficacy of AVERT by finding a correlation between trainee route selection and hazard exposure in a set of test scenarios.

Human Factor Risk Assessment During Emergency Condition in Harsh Environment

This paper presents a quantitative approach to human factors risk analysis during emergency conditions on an offshore petroleum facility located in a harsh environment. Due to the lack of human factors data for emergency conditions, most of the available human factors risk assessment methodologies are based on expert judgment techniques. Expert judgment is a valuable technique, however, it suffers from vagueness, subjectivity and incompleteness due to a lack of supporting empirical evidence. These weaknesses are often not accounted for in conventional human factors risk assessment. The available approaches also suffer from the unrealistic assumption of independence of the human performance shaping (HPS) factors and actions. The focus of this paper is to address the issue of handling uncertainty associated with expert judgments and to account for the dependency among the HPS factors and actions. These outcomes are achieved by integrating Bayesian Networks with Fuzzy and Evidence theories to estimate human error probabilities during different phases of an emergency. To test the applicability of the approach, results are compared with an analytical approach. The study demonstrates that the proposed approach is effective in assessing human error probability, which in turn improves reliability and auditability of human factors risk assessment.

A complexity study of human-machine interaction on motion platforms

This paper presents a quantitative complexity theory for human-machine interaction and validates the developed theory through experiments. Based on work in basic research an information-theoretic complexity measure C is introduced The main advantage of the novel measure is that it solely relies on information theoretic quantities and is independent from possibly unreliable subjective ratings or psychophysiological measurements. The validity of the complexity measure is studied through interactive visual search experiments with electronic chart displays for vessel navigation and control. The experiments were carried out in a high fidelity marine simulator with 30 participants. The platform motion and the ambient light conditions were varied systematically. The results show a significantly lower interaction complexity when the simulator is put in sea state characteristics and the operator is facing considerable motion forces. In addition, significantly lower complexity values were observed, if the ambient light intensity is reduced from 800 Lux (daylight) to 30 Lux (twilight). Under the daylight condition the average complexity reduction due to the platform motion was 10%. However, under the twilight condition there was a stronger average complexity reduction with 17%. Therefore, the novel complexity theory seems to be a valid approach for the quantitative assessment of human machine interaction on motion platforms

Achieving Competence in Offshore Emergency Egress Using Virtual Environment Training

As a precursor to simulation transfer studies, this research assessed the level of competence in basic offshore safety gained through a virtual environment training program and investigated the training time required to reach competence. The experiment demonstrated that the offshore egress learning objectives can be taught using the All-hands Virtual Emergency Response Trainer (AVERT) training program with some limitations. The two main findings were: 1. due to individual differences in spatial learning, some individuals required more exposure to the virtual setting to ensure knowledge retention; and 2. the procedural learning objectives required reinforcement during training scenarios to ensure knowledge acquisition. Overall, this research recommends modifications to the training and technology design in order to prepare for future transfer studies and offshore applications.Copyright

Using a Dacon Scoop to Recover a Loaded Liferaft at Sea

Service and supply vessels that perform standby duties in the offshore sector are equipped with a variety of resources with which to perform rescue at sea. For light to moderate sea conditions, techniques currently understood and practiced tend to involve using a fast rescue craft (FRC) to rescue survivors and subsequently transfer them to a safe haven (often a standby vessel). Rescuing evacuees in higher, more challenging sea states, however, is difficult given that it can be unsafe to launch and recover FRCs in such conditions. For these cases, many standby vessels in Eastern Canada and the North Sea are equipped with a device called a Dacon Scoop. The Dacon Scoop is a 6 to 8m semi-rigid net that is deployed directly from the side of the standby vessel and designed to rescue people directly from the water. While not a conventional use, it has been suggested that the scoop could also be used to recover small rescue craft (life rafts, lifeboats and fast rescue craft) at sea. Although life rafts provide occupants with some protection from the elements, there are still issues that can make it less than desirable to remain inside for extended periods of time if an effective means of system recovery is available. This paper presents the findings of research carried-out to determine if it is safe to use a Dacon Scoop to recover a loaded liferaft. The research trials made use of a loaded inflatable 25 person davit launched life raft and two different standby vessels 75m in length. A total of 34 tests were carried out over three days in significant wave heights up to 3.7m. Recommendations are given in the context of a human factor assessment related to the procedures, equipment and field trials experiences.Copyright

Free-Fall Lifeboats: Experimental Investigation of the Impact of Environmental Conditions on Technical and Human Performance

Free-fall lifeboats offer a means to evacuate a ship or offshore installation rapidly, without the lowering operations associated with conventional davit launched lifeboats on wire falls. The performance of free-fall lifeboats during launch and sail-away has been investigated using a model test campaign. The main focus of the experimental evaluation was on the performance of this evacuation system in a range of different weather conditions. Measurements were also made of motions during the launch process, which are relevant to occupational safety issues. Examples of the tests are presented with a focus on results that warrant scrutiny in terms of human health and performance. The results lead us to question the IMO criteria used to assess the occupational safety of free-fall lifeboats.Copyright