Modeling trajectories of perceived leg exertion during maximal cycle ergometer exercise in children and adolescents

Abstract

BackgroundBorg developed scales for rating pain and perceived exertion in adults that have also been used in pediatric populations. Models describing functional relationships between perceived exertion and work capacity have not been studied in children. We compared different models and their fits to individual trajectories and assessed the variability in these trajectories.MethodsRatings of perceived exertion (RPE) were collected from 79 children. Progressive cycle ergonometric testing was performed to maximal work capacity with test duration ranging from 6‐ 12 minutes. Ratings were obtained during each 1‐minute increment. Work was normalized to individual maximal work capacity (Wmax). A delay was defined as the fraction of Wmax at which point an increase in ratings of leg fatigue occurred. Such a delay term allows the characterization of trajectories for children whose ratings were initially constant with increasing work. Two models were considered, a delay model and a power model that is commonly used to analyze Borg ratings. Individual model fit was assessed with root mean squared error (RMSE). Functional clustering algorithms were used to identify patterns.ResultsLeg tiredness developed quickly for some children while for others there was a delay before an in‐ creased ratings of leg exertion occurred with increasing work. Models for individual trajectories with the smallest RMSE included a delay and a quadratic term (quadratic‐delay model), or a power function and a delay term (power‐delay model) compared to a simple power function. The median delay was 40% Wmax (interquartile range (IQR): 26‐49%) in a quadratic‐delay model, while the median exponent was 1.03 (IQR: 0.83‐1.78) in a power‐delay model. Nine clusters were identified showing linear or quadratic patterns with or without a delay. Cluster membership did not depend on age, gender or diagnosis.ConclusionChildren and adolescents vary widely in their capacity to rate their perceptions and exhibit different functional relationships between ratings of perceived exertion and work capacity normalized across individuals. Models including a delay term, a linear component, or a power function can describe these individual trajectories of perceived leg exertion during incremental exercise to voluntary exhaustion.

Dalhousie Pictorial Scales Measuring Dyspnea and Perceived Exertion during Exercise for Children and Adolescents

“…This figure also illustrates well the principal reason for the marked interindividual variability in ratings that we detailed previously (13,14) (i.e., the delay or "lag" during incremental exercise before ratings of perceived exertion or dyspnea rose above resting levels). Such a trajectory during ORIGINAL RESEARCH exercise with short (1 min) duration at each level resulted in the leftward, long, flat leader in plots shown in Figure 3 before perceived sensation finally began to rise in heavy exercise in some subjects, whereas in other subjects the rise occurred early, during light exercise.…”

“…In other words, children and adolescents seem to require greater change in stimulus intensity (resistance in cited studies) above resting level before reporting a change in sensation. Although inability to detect or report change in sensory perceptions slightly above resting levels explains relative insensitivity at the lower ends of the Dalhousie or Borg scales, many subjects reported dyspnea or perceived exertion values below the highest possible rating on either scale (Table 2), a finding discussed in our prior publications (13,14) and reported by others using other rating scales (25). Table 2 shows Borg ratings at peak exercise averaged close to 50% of maximum values for dyspnea and perceived exertion, respectively, while reaching 64% (4.5/7) and 70% (4.9/7) for dyspnea and perceived exertion of maximum Dalhousie scale ratings, respectively.…”

“…We have already reported extensive analyses of Borg ratings during exercise in children (13,14). Therefore, they are reported here merely for purposes of comparison with Dalhousie ratings of dyspnea and perceived exertion.…”

“…There was considerable intersubject variability in that study, which was also problematic as we described a mathematical model of the sensory response for ratings of dyspnea and perceived exertion during incremental exercise to voluntary exhaustion. Many children reported no change in perceived exertion above resting level until work exceeded one-third peak work capacity (13), and we recently extended these findings to describe ratings of exertional dyspnea in a pediatric population (14).…”

Dalhousie Dyspnea and Perceived Exertion Scales: Psychophysical properties in children and adolescents

“…Scale design has been described (McGrath, Pianosi, Unruh, Smith, 2005) and the scales accurately tracked dyspnea during histamine-induced bronchoconstriction (Pianosi, Smith, Almudevar, & McGrath, 2006). We recently showed that ratings of perceived exertion obtained using the Borg CR-10 scale in children and adolescents conformed equally well to a quadratic function as to a power function, but goodness of fit was improved by introducing a delay term to account for the lag observed before these sensations were perceived (or reported) to exceed resting levels (Huebner, Zhang, McGrath, Therneau, & Pianosi, 2014). The aims of the present report were to demonstrate concurrent validity and describe the trajectory of dyspnea and perceived exertion ratings obtained using these pictorial scales in children and adolescents.…”