A computer-based instrumentation system which accurately measures the seat, handlebar, and pedal loads together with the absolute pedal position during bicycling is presented. The instrumentation system is unique in that for the first time it allows measurement of handlebar and seat loads. With three test subjects riding on rollers, which simulate actual bicycling, loading data were recorded at constant power for different pedaling rates. Analysis of the data enables load characteristics of all three sources (i.e., pedal, seat, and handlebar) to be categorized as being either subject and pedaling rate independent or subject independent but pedaling rate dependent. A complete set of loading data for one subject is presented to illustrate these characteristics. One interesting finding is that peak levels of all but one of the pedal loads are inversely related to pedaling rate. Peak levels of seat and handlebar loads reactive to the driving loads on the pedals, however, are directly related to pedaling rate. Another interesting result is that handlebar and seat loads, except for the lateral seat moment, go through two cycles for each revolution of the crank arm. The interpretation of these results, as well as others, provides insight into the biomechanics of the pedaling process.
Farhad Bolourchi and M.L. Hull
Glenn M. Street and Edward C. Frederick
This paper describes a system that was developed to measure ski pole and roller-ski reaction forces in three dimensions during roller-ski skating. Uni-axial force transducers mounted in the right and left ski poles measure axial loading of the poles. Six transducers in one roller-ski measure biaxial loads beneath the foot. A remote computer stores the amplified transducer signals transmitted from the skier through 100 m cables. Three-dimensional video-graphy determines the orientations of the poles and roller-ski in order to resolve the resultant poling and skating forces into three components. Calibration data suggest that the resolution of the force measurement system is ±3 to 9% of the actual poling and skating forces, respectively. Sample data are presented from a VI skating trial during roller-skiing. These data provide the first glimpse at the major functions of the upper and lower body during roller-ski skating and show how the tool could be used to examine the size and effectiveness of skier-generated forces.
Gerald Barber and Charles T. Heise
Although not well validated, physicians frequently use subjective estimates of exercise ability to assess clinical status and therapeutic results. This study employed a standardized questionnaire and cardiopulmonary exercise test to compare the results of subjective estimates by 211 patients (mean age 13.9 yrs) with objective measurements of exercise ability. Questionnaire data correlated with measured maximal oxygen consumption. Individuals thought to be below average had a maximal oxygen consumption of 21±6 ml/kg/min. Those thought to have average fitness had a maximal oxygen consumption of 26±8 ml/kg/min, and those thought to be above average had a maximal oxygen consumption of 30±7 ml/kg/min. There was a great degree of overlap and scatter of these data, however, such that questionnaire data significantly overestimated exercise ability in 67% and underestimated it in 3% of the subjects. In only 30% of the subjects did the subjective estimate of exercise ability correspond with objectively measured exercise ability. It was concluded that subjective estimates are unreliable and should not be used in assessing the functional status of an individual patient, but subjective estimates may give some idea of objective capabilities in large population studies.
Kent C. Kowalski and Peter R.E. Crocker
Two studies reported the development and validation of the Coping Function Questionnaire (CFQ) for adolescent sport participants. The purpose of the first study was to develop the CFQ and conduct preliminary item and scale analyses. The result was an 18-item CFQ, which assessed problem-focused, emotion-focused, and avoidance coping function. In the second study, confirmatory factor analysis with data from 344 male and 339 female adolescent sport participants showed the CFQ measurement model to be acceptable for both genders. Simultaneous group analysis demonstrated gender invariance for the CFQ measurement model. Convergent and divergent validity was supported by correlations between the CFQ and select coping scales from the COPE, the sport-modified COPE, and Life Situations Inventory. The CFQ appears to be a promising step toward measurement of coping function in adolescent sport samples.
Jason C. Holmes, Ann L. Gibson, J. Gualberto Cremades and Constance M. Mier
To compare estimates of body density (Db) from air-displacement plethysmography (ADP) with measured and predicted thoracic-gas-volume (TGV) measurements and those from hydrodensitometry (HD) in children.
Seventeen participants (13 male and 4 female; 10.1 ± 2.20 yr, 42.0 ± 15.03 kg, 145.6 ± 17.41 cm, 30.0 ± 8.66 kg/m2) were tested using ADP and HD, with ADP always preceding HD. Db estimates were compared between ADP with measured TGV, ADP with predicted TGV, and the reference measure, HD. Regression analyses were used to assess the accuracy of the ADP methods, and potential bias between the ADP procedures and HD were evaluated using Bland–Altman analyses. The cross-validation criteria described by Lohman for estimating Db relative to HD were used to interpret the results of the study.
A significant difference was found between Db estimates from ADP with measured TGV (1.0453 ± 0.01934 g/cm3) and ADP with predicted TGV (1.0415 ± 0.01858 g/cm3); however, neither was significantly different from Db obtained by the reference HD procedure (1.0417 ± 0.02391 g/cm3). For both ADP procedures, regression analyses produced an r = .737–.738, r 2 = .543−.544, and SEE = 0.02 g/cm3, and the regression lines deviated significantly from the line of identity; however, no significant biases were indicated.
Despite no significant mean differences between Db estimates from the ADP procedures and HD, more cross-validation research is needed before recommending the BOD POD for routine use with children in clinical and research settings.
Richard W. Bohannon and A. Williams Andrews
Overall muscle strength of extremities is often characterized by measurements from one or more selected actions. This study evaluated the legitimacy of that procedure. Measurements obtained by handheld dynamometry from 13 muscle actions of 156 apparently healthy individuals (50–79 years) were subjected to correlational analysis, principal-components analysis, and cluster analysis. The isometric strengths of all muscle actions correlated significantly with one another (r = .506–.965). Principal-components analysis without rotation showed that all tested actions loaded highly on overall limb muscle strength. Principal-componcnis analysis with varimax rotation revealed high loadings that were grouped by extremity (upper vs. lower). Ankle dorsiflexion strengths were exceptions. These findings, in conjunction with the cluster analysis, support using one or more actions to characterize isometric limb muscle strength among the elderly but suggest that muscle strength in an upper or lower extremity is best characterized by an action (e.g., elbow flexion) of that extremity.
Yvonne Michael, Tracey Beard, Dongseok Choi, Stephanie Farquhar and Nichole Carlson
There is a need for greater understanding of how perceptions and objective measures of the physical environment influence physical activity among seniors. The goal of this study was to examine the degree of association between perceived and objective characteristics of the neighborhood environment and the relation of each type of measurement to neighborhood walking in older adults. Data on self-reported frequency of walking in the neighborhood and perceived measures of neighborhood environment from 105 older adults were linked to objective measures assessed by geographic information systems and an audit instrument. Perceived and objective measurements of the built environment exhibited a low degree of agreement (kappas: <.20). After adjustment for education, age, and gender, presence of a mall was positively associated with neighborhood walking in both the objective and perceived models.
Lauren Waters, Marina Reeves, Brianna Fjeldsoe and Elizabeth Eakin
Several recent physical activity intervention trials have reported physical activity improvements in control group participants. Explanations have been proposed, but not systematically investigated.
A systematic review of physical activity intervention trials was conducted to investigate the frequency of meaningful improvements in physical activity among control group participants (increase of ≥ 60 minutes [4 MET·hours] of moderate-to-vigorous physical activity per week, or a 10% increase in the proportion of participants meeting physical activity recommendations), and possible explanatory factors. Explanatory factors include aspects of behavioral measurement, participant characteristics, and control group treatment.
Eight (28%) of 29 studies reviewed reported meaningful improvements in control group physical activity, most of which were of similar magnitude to improvements observed in the intervention group. A number of factors were related to meaningful control group improvements in physical activity, including the number of assessments, mode of measurement administration, screening to exclude active participants, and preexisting health status.
Control group improvement in physical activity intervention trials is not uncommon and may be associated with behavioral measurement and participant characteristics. Associations observed in this review should be evaluated empirically in future research. Such studies may inform minimal contact approaches to physical activity promotion.
E. Andrew Pitchford, Leah R. Ketcheson, Hyun-Jin Kwon and Dale A. Ulrich
Research measuring physical activity behaviors during infancy is critical for evaluation of early intervention efforts to reduce rapid weight gain. There is little known about the physical activity patterns of infants, due in part to limited evidence for measurement procedures. This study sought to determine the minimal number of days and hours of accelerometry needed to reliably measure daily physical activity in infants using Generalizability (G) theory.
A total of 23 infants (14 female, 9 male) wore an accelerometer on the right ankle and right wrist for 7 days. Data were manually cleaned to remove activity counts not produced by the infant. G theory analyses were conducted on the average counts per epoch.
Reliable estimates were observed with at least 2 days (G & Φ = .910) and 12 hours (G = .806, Φ = .803) at the ankle, and with at least 3 days (G & Φ = .906) and 15 hours (G = .802, Φ = .800) at the wrist.
These results provide some of the first guidelines for objective physical activity measurement during infancy. Accelerometer monitoring periods of at least 3 days including all daytime hours appear to be sufficient for reliable measurement.
Jennifer L. Copeland, Kent C. Kowalski, Rachel M. Donen and Mark S. Tremblay
To accommodate the need for longitudinal physical activity research, we developed the Physical Activity Questionnaire for Adults (PAQ-AD). The PAQ-AD is an adult version of the PAQ-C and PAQ-A questionnaires which were developed for older children and adolescents, respectively.
Two studies assessed the convergent validity of the PAQ-AD using a series of self-report tools and direct measurement of physical activity.
In the first sample (N = 247), the PAQ-AD was significantly related to a series of self-report tools (r = 0.53 to 0.64). In the second sample (N = 184), the PAQ-AD was significantly related to the self-report tools (r = 0.56 to 0.63), a physical activity recall interview (r = 0.24), and to direct measurements of physical activity (r = 0.26 to 0.43).
These results provide preliminary validity evidence for the PAQ-AD and suggest the PAQ “family” of questionnaires might be advantageous for longitudinal research assessing physical activity from childhood to adulthood.