The study of dual task interference has gained increasing attention in the literature for the past 35 years, with six MEDLINE citations in 1979 growing to 351 citations indexed in 2014 and a peak of 454 cited papers in 2013. Increasingly, researchers are examining dual task cost in individuals with pathology, including those with neurodegenerative diseases. While the influence of these papers has extended from the laboratory to the clinic, the field has evolved without clear definitions of commonly used terms and with extreme variations in experimental procedures. As a result, it is difficult to examine the interference literature as a single body of work. In this paper we present a new taxonomy for classifying cognitive-motor and motor-motor interference within the study of dual task behaviors that connects traditional concepts of learning and principles of motor control with current issues of multitasking analysis. As a first step in the process we provide an operational definition of dual task, distinguishing it from a complex single task. We present this new taxonomy, inclusive of both cognitive and motor modalities, as a working model; one that we hope will generate discussion and create a framework from which one can view previous studies and develop questions of interest.

The purpose of this article is to provide a brief review of the principles of motor control and learning. Different models of motor control from historical to contemporary are presented with emphasis on the Systems model. Concepts of motor learning including skill acquisition, measurement of learning, and methods to promote skill acquisition by examining the many facets of practice scheduling and use of feedback are provided. A fictional client case is introduced and threaded throughout the article to facilitate understanding of these concepts and how they can be applied to clinical practice.

Exercise has been recommended as a way to maintain quality of life in individuals with Parkinson disease (PD). Experiments examining the cardiovascular response to exercise, however, have yielded controversial results. This study was designed to determine if there is any difference in vital signs and Rate of Perceived Exertion (RPE) between a group of individuals (50–80 years old) with PD and a comparison group of healthy individuals during exercise on a treadmill. Twenty seven volunteers (16 with PD and 11 healthy) participated in this study. Subjects with PD were divided into 2 groups; one that reached target heart rate and one that failed to reach it. In this study, heart rate (HR), systolic blood pressure (BP), and the RPE were measured during a Modified Bruce Protocol. We hypothesized that treadmill testing would result in differences between individuals with PD and healthy subjects when HR and systolic BP were compared at submaximal exercise (defined as Stage 2 of the Modified Bruce Protocol) and at peak exercise (defined as 85% of age predicted target heart rate). During submaximal exercise, no significant differences were found between the PD group and the control group for HR, B P, or RPE. At peak exercise, one half of the subjects with PD exhibited blunted cardiovascular responses, despite reaching a comparable intensity of exercise during a Modified Bruce Protocol. Although cardiovascular responses to exercise on a treadmill appear similar between individuals with PD and controls at lower levels of exercise, half the subjects with PD in the present study displayed abnormal cardiovascular responses at higher exercise intensities. Administering an exercise stress test will illustrate the expected cardiovascular responses for each individual, therefore guiding exercise prescription.

Study Design: Case control, repeated-measures, experimental laboratory study. Objective: To determine if, during a whole-body lifting task, individuals with low back pain (LBP) breathe differently than age-matched controls. Background: Breath control may be optimized to provide increased intersegmental control of the lumbar spine through the generation of intra-abdominal pressure. Consequently, impairments in respiratory and trunk muscle coordination during lifting tasks may contribute to the occurrence or maintenance of LBP. Methods: Participants without LBP (n = 30) were matched by gender and age with those presenting with chronic mechanical LBP (n = 32) of at least 1 year in duration. Participants completed a total of 8 self-paced lifts of a crate from the floor to a table, with the crate empty during 4 of the lifts and loaded to 25% of the participant's body weight during 4 of the lifts. The amount of volume in the lungs, measured as a percentage of the individual's vital capacity (%VC), was identified at 9 points during the lifting task. A 2 × 2 × 2 × 9 (group by gender by load by time) mixed-model analysis of covariance (ANCOVA), with age as the covariate, was used to identify differences among conditions and groups of %VC used during the lift. Results: Individuals with LBP performed the lifting task with more volume in their lungs (48.2 %VC) than healthy peers (40.9 %VC). Age significantly affected %VC used during the lift: with increasing age, participants with LBP increased inspired volume and participants without LBP decreased inspired volume. Conclusions: Individuals with LBP performed a lifting task with more inhaled lung volume than individuals without LBP. These findings are consistent with the theoretical link between breath control, intra-abdominal pressure, and lumbar segmental control. J Orthop Sports Phys Ther 2011;41(3):141–148, Epub 4 January 2011. doi:10.2519/jospt.2011.3437