Purpose: To determine if the Physiological Strain Index (PSI), in original or modified form, can evaluate heat strain on a 0–10 scale, in trained and heat-acclimatized men undertaking a competitive half-marathon run in outdoor heat. Methods: Core (intestinal) temperature (TC) and heart rate (HR) were recorded continuously in 24 men (mean [SD] age = 26 [3] y, VO2peak = 59 [5] mL·kg·min−1). A total of 4 versions of the PSI were computed: original PSI with upper constraints of TC 39.5°C and HR 180 beats·min−1 (PSI39.5/180) and 3 modified versions of PSI with each having an age-predicted maximal HR constraint and graded TC constraints of 40.0°C (PSI40.0/PHRmax), 40.5°C (PSI40.5/PHRmax), and 41.0°C (PSI41.0/PHRmax). Results: In a warm (26.1–27.3°C) and humid (79–82%) environment, all runners finished the race asymptomatic in 107 (10) (91–137) min. Peak TC and HR were 39.7°C (0.5°C) (38.5–40.7°C) and 186 (6) (175–196) beats·min−1, respectively. In total, 63% exceeded TC 39.5°C, 71% exceeded HR 180 beats·min−1, and 50% exceeded both of the original PSI upper TC and HR constraints. The computed heat strain was significantly greater with PSI39.5/180 than all other methods (P < .003). PSI >10 was observed in 63% of runners with PSI39.5/180, 25% for PSI40.0/PHRmax, 8% for PSI40.5/PHRmax, and 0% for PSI41.0/PHRmax. Conclusions: The PSI was able to quantify heat strain on a 0–10 scale in trained and heat-acclimatized men undertaking a half-marathon race in outdoor heat, but only when the upper TC and HR constraints were modified to 41.0°C and age-predicted maximal HR, respectively.
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The Physiological Strain Index Modified for Trained Heat-Acclimatized Individuals in Outdoor Heat
Christopher Byrne and Jason K.W. Lee
“There’s a Lifestyle, an Appreciation, a Beauty”: An Interpretative Phenomenological Analysis of Masters Rowers
Jason Rich, Pamela Beach, and Heidi K. Byrne
Masters rowing has seen a measurable increase in participation, with masters rowers engaged in the sport for competition, health, and recreation reasons. Unlike other masters sports, masters rowing has a unique high level of synchronous, cooperative, and interdependent elements. To better understand the benefits and challenges of participation in competitive masters rowing, the purpose of this study was to explore the lived experiences of competitive masters rowers. Twelve competitive masters rowers were recruited and interviewed. Utilizing an interpretative phenomenological analysis approach to guide data collection, analysis, and interpretation, the analysis revealed four major themes: navigating community relationships, finding a reason to row, growing opportunities, and seeking considerate coaches. Utilizing self-determination theory as a framework for interpreting the findings, the identified themes illustrate the varying motivations, needs, and preferences of competitive masters rowers, as well as how their experiences are influenced by their coaches and peers. Efforts should be made by masters rowing coaches and administrators to better understand the needs of their athletes to ensure the maximum benefits of participation, commitment, and enjoyment of the sport.
Continuous Thermoregulatory Responses to a Mass-Participation 89-km Ultramarathon Road Race
Christopher Byrne, Aurelien Cosnefroy, Roger Eston, Jason K.W. Lee, and Tim Noakes
Purpose: To continuously measure body core temperature (T c) throughout a mass-participation ultramarathon in subelite recreational runners to quantify T c magnitude and the influence of aerobic fitness and body fat. Methods: Twenty-three participants (19 men and 4 women; age 45 [9] y; body mass 72.0 [9.3] kg; body fat 26% [6%]; peak oxygen uptake 50 [6] mL·kg−1·min−1) had gastrointestinal temperature measured during an 89-km ultramarathon. Prerace-to-postrace changes in body mass, plasma sodium, and fluid and food recall quantified body water balance. Results: In maximal environmental conditions of 26.3 °C and 53% humidity, 21 of the 23 participants finished in 10:28 (01:10) h:min while replacing 49% (27%) of sweat losses, maintaining plasma sodium (140 [3] mmol·L−1), and dehydrating by 4.1% (1.3%). Mean maximum T c was 39.0 (0.5) (range 38.2–40.1 °C) with 90% of race duration ≤39.0 °C. Mean maximum ΔT c was 1.9 (0.9) (0.9–2.7 °C) with 95% of race duration ≤2.0 °C. Over 0 to 45 km, associations between ΔT c and peak oxygen uptake (positive) and body fat (negative) were observed. Over 58 to 89 km, associations between T c and peak oxygen uptake (negative) and body fat (positive) were observed. Conclusions: Modest T c responses were observed in recreational ultramarathon runners. Runners with higher levels of aerobic fitness and lower levels of body fat demonstrated the greatest changes in T c during the first half of the race. Conversely, runners with lower levels of aerobic fitness and higher levels of body fat demonstrated the greatest absolute T c in the final third of the race.
The Association of Trail Features With Self-Report Trail Use by Neighborhood Residents
Christopher Johansen, Kim D. Reynolds, Jennifer Wolch, Jason Byrne, Chih-Ping Chou, Sarah Boyle, Donna Spruijt-Metz, Brianna A. Lienemann, Susan Weaver, and Michael Jerrett
Background: Urban trails are a useful resource to promote physical activity. This study identified features of urban trails that correlated with trail use. Methods: Multiuse urban trails were selected in Chicago, Dallas, and Los Angeles. An audit of each trail was completed using the Systematic Pedestrian and Cyclist Environmental Scan for Trails instrument, identifying built environmental features. A self-report of trail use was obtained from trailside residents (N = 331) living within 1 mile of each trail. Univariate and multivariate Poisson regressions controlled for trail time from home and motivation for physical activity. Results: Positive associations with the past month’s hours on the trail were observed for the presence of distance signs, vegetation height, vegetation maintenance, and trail crowding, and a negative association was observed for the presence of crossings on the trail. Positive associations with dichotomous trail use were observed for the presence of distance signs, vegetation height, and vegetation maintenance, and a negative association was observed for the presence of crossings on the trail. Conclusions: These correlates should be confirmed in other studies and, if supported, should be considered in the promotion and design of urban trails.
Reasons for Urban Trail Use Predict Levels of Trail-Related Physical Activity
Genevieve Fridlund Dunton, Donna Spruijt-Metz, Jennifer Wolch, Chih-Ping Chou, Michael Jerrett, Jason Byrne, Susan Weaver, and Kim D. Reynolds
Background:
Efforts to increase community levels of physical activity through the development of multiuse urban trails could be strengthened by information about factors predicting trail use. This study examined whether reasons for trail use predict levels of physical activity on urban trails.
Methods:
Adults (N = 335) living within a 1-mile buffer zone of urban trails in Chicago, Dallas, and Los Angeles completed a self-report measure assessing demographics, reason for trail use, and physical activity on the trail. Accelerometers measured total daily moderate-to-vigorous physical activity (MVPA). Environmental features of the urban trail were assessed with the Systematic Pedestrian and Cyclist Environmental Scan for trails measure. Multivariate regression analyses were conducted that accounted for clustering of individuals within trail segments.
Results:
After controlling for demographic and environmental factors and total daily MVPA, reasons for trail use significantly predicted recreational but not transportation activity. Recreational trail activity was greater for participants who reported exercise and health reasons for trail use as compared with other reasons (ie, social interaction, enjoying nature, walking pets) for recreational trail use.
Conclusions:
To increase the use of urban trails, it may be useful to promote the health and exercise benefits of recreational trail use.
