Towards the establishment of a worker-centered framework to physically prepare firefighters: The evaluation of movement and the transfer of training
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Firefighter injuries are a billion dollar problem every year with an even larger human impact. Substantial efforts have been made to reduce the associated costs, yet many of the injuries sustained are the director result of efforts to become better physically prepared. Because firefighters depend on their physical abilities to perform safely and effectively, worker-centered strategies, wherein an emphasis is placed on how individuals perform are needed. However, to date, there is little evidence to help guide the evaluation of an individual’s movement patterns, particularly within the context of their occupation, and even less known about the transfer of training. To assist in the establishment of a worker-centered framework that can be used to physically prepare firefighters, four studies were conducted to address the following global thesis objectives: 1) Examine the impact of task and environmental constraints on individuals’ movement behaviour. 2) Examine the impact of exercise on individuals’ movement behaviour. 3) Examine the homogeneity of individuals’ movement behaviour. Study 1: Movement variability and the estimation of “meaningful” change Background: The within-subject variation may offer a viable means to examine the individual so that studies are not limited to group analyses. Study objectives were to examine the within-subject variation and between-session repeatability of select descriptors of motion and evaluate the potential in using the within-subject variation as a criterion with which to define biologically significant or “meaningful” within-subject differences. Methods: Twenty professional firefighters were assigned to a lifting or firefighter group, each completing three testing sessions. Participants performed 25 repetitions of two lifting (heavy and light) or two simulated firefighting tasks (hose advance, forced entry). The magnitude and within-subject variation of select kinematic measures were described for each session, and sequential averaging was used to explore the efficacy of using the within-subject variability to define “meaningful” within-subject differences. Results: All dependent measures were repeatable for each of the four tasks examined; however, the individuals did not exhibit the same movement patterns as were demonstrated by the group. Using only 2 (of 25) repetitions, the within-subject variation successfully captured the 25-trial variation in 70% of all instances; using 3, 5, and 10 trials increased the success rate to 74%, 81% and 89%, respectively. Conclusions: Aggregate data may not represent that of the individuals, and therefore it might be important to examine within-subject changes to correctly interpret the effects of an intervention. The within-subject variation may offer a simple means to accommodate participants’ variability without having to collect a large number of trials, and thus could provide a tremendous opportunity to explore various interventions designed to prevent musculoskeletal injury or improve performance. Study 2: Load, speed and the evaluation of movement: A task’s demands influence the way we move Background: If individuals adapt their movement patterns in response to the demands of a task, the utility of movement evaluations comprising only low demand activities could be limited. The study objective was to determine whether individuals adjust their movement patterns in response to variation of the external load and speed of movement. Methods: Fifty-two professional firefighters performed five low-demand (i.e. light load, low movement speed) whole-body tasks (i.e. lift, squat, lunge, push, pull). Once each task had been performed its demands were modified by increasing the movement speed, external load, or speed and load. Select measures of motion were used to characterize the performance of each task and comparisons were made between conditions. Results: Participants adapted their movement patterns in response to the demands of a task (64% and 70% of all variables were influenced (p<0.05) by changing the load and speed, respectively), but in a manner unique to the task and type of demand in question, and not always in the same way as that of the group. During the first phase of each task, there were 246 individual “meaningful” negative adaptations observed in response to an increase in speed, but only 125 in response to the heavier loads. Conclusions: Simply because an individual exhibits the ability to perform a low-demand task does not imply that they will also be physically prepared to perform safely or effectively when the task’s demands are increased. Movement screens comprising only low demand activities may not adequately reflect an individual’s capacity, or their risk of injury, and could skew any recommendations that are made for training. Study 3: The predictive value of general movement tasks in assessing occupational task performance Background: Attempts to generalize the results of a movement evaluation or screen may lead to inaccurate characterizations (e.g. high risk) and inappropriate recommendations for training. The study objective was to investigate whether a battery of general tasks could be used to describe the movement patterns adopted to perform select job-specific skills. Methods: Fifty-two professional firefighters performed a battery of general (i.e. lift, squat, lunge, push and pull) and occupation-specific (i.e. chop, forced entry, hose drag, hose pull, heavy drag) tasks that simulated the demands of firefighting. Participants’ peak spine flexion, range of spine lateral bend and twist, and peak medial displacement of each knee in the frontal plane were compared across tasks. Results: The general tasks could be used to estimate the magnitude of spine and frontal plane knee motion adopted while performing the battery of complex firefighting-specific skills. In only 14.6% of all instances across variables and tasks were individuals’ general task scores not greater than those observed during the firefighter skills. There may be attributes, or “key features”, of an individual’s movement behaviour that can be used to generalize their movement competency across a range of activities. Conclusions: The findings provide support for the notion that a general whole-body movement evaluation, or pre-participation screen, can be used to estimate an individual’s risk of injury or make recommendations for training, provided that the screening tasks are chosen and administered in such a way that they challenge participants’ capacity to control the motions of interest. Study 4: Periodized exercise and the transfer of training: Can we change the way an individual moves? Background: Exercise programs that emphasize fitness characteristics and performance outcomes alone may not offer an effective means to elevate one’s level of physical preparedness. The study objective was to examine the adaptations (fitness and movement) exhibited by professional firefighters in response to two training methodologies, differing most notably in the attention that was given to how each exercise was performed. Five tasks not included in the interventions were used to evaluate the transfer of training. Methods: Fifty-two firefighters were assigned to a “movement-oriented fitness” training (MOV), “fitness” training or control (CON) group. Before and after 12 weeks of exercise, subjects performed a comprehensive fitness evaluation and laboratory test, comprising five general whole-body tasks. Participants’ peak spine flexion, range of lateral bend and twist, and peak medial displacement of each knee in the frontal plane were quantified. Results: FIT and MOV exhibited significant improvements in nearly all aspects of fitness tested; however, only MOV demonstrated less joint motion while performing each transfer task. FIT showed select improvements, although spine flexion and frontal plane knee motion increased while squatting, lunging, pushing and pulling. More and fewer MOV participants exhibited only positive and negative “meaningful” post-training changes, respectively, in comparison to the FIT and CON groups. Conclusions: A well-designed exercise program can be used to change an individual’s habitual movement patterns, which for occupational athletes such as firefighters, soldiers and police officers, implies that training can have a direct impact on their safety and effectiveness. However, emphasizing fitness characteristics and performance outcomes alone may not be the most effective strategy to reduce one’s risk of injury or elevate their level of preparedness. Summary and Conclusions: An individual’s movement patterns are variable and influenced by the task and environmental constraints (e.g. speed of movement). Therefore, whether attempting to prevent injury, enhance performance or improve one’s quality of life, any physical preparation program should give adequate consideration to the individuals’ adaptations. When focused solely on the group’s behaviour, there is greater opportunity to skew the interpretation of any findings and overlook several important and potentially novel insights regarding the movement-related adaptations that are exhibited by each individual in response to the particular stimulus, demand, or exercise being investigated. Although several novel insights were provided by the findings of this thesis, the most practical and perhaps influential was that a well-designed exercise program can change an individual’s habitual movement patterns. A group of firefighters with little knowledge or appreciation for how they move, exhibited more control and coordination while performing five whole-body transfer tasks following twelve weeks of training. There is no single exercise or coaching cue that can be used to improve every individual’s capacity; however, one inappropriate recommendation can negate any potential benefit that a program can offer. Consequently, critical to the establishment of a worker-centered framework to physically prepare firefighters is an appreciation for movement and the transfer of training.