ECSS Paris 2023: CP-PN22
INTRODUCTION: The speed-duration relationship describes the hyperbolic relationship between running speed and time to task failure. Critical speed (CS) is the asymptote of this relationship, defining the boundary between heavy and severe exercise intensity domains, below which a metabolic steady state can be achieved. The curvature constant D' represents a finite distance capacity available when running at speeds >CS before task failure. These parameters are strongly related to middle-distance running performance, with CS broadly reflecting sustainable oxidative energy production and D' the finite capacity for substrate-level phosphorylation. Although laboratory-based constant-speed time-to-exhaustion (TTE) protocols are often considered the gold standard for assessing the speed-duration relationship, the reproducibility of CS and D' derived from TTE trials has not been examined. Therefore, this study aimed to assess the test-retest reliability of CS and D' using TTE trials in well-trained runners. METHODS: Five male (age 25 ± 6 y; maximal oxygen uptake (VO2max) 68 ± 6 mL/kg/min) and 5 female (age 26 ± 7 y; VO2max 57 ± 5 mL/kg/min) well-trained distance runners attended the laboratory on five occasions, each separated by 3-7 days. The first visit characterised blood lactate responses to increased running speed and quantified VO2max. Participants subsequently completed 4 constant-speed TTE trials across visits 2-3 (60 min passive recovery between runs within visits) on a motorised treadmill (1% gradient) at speeds spanning 50% delta to sVO2max to elicit exhaustion between ~2-15 min. The same 4 speeds were repeated in the identical order for each participant during visits 4-5 to allow test-retest analysis. CS and D' were estimated using three two-parameter models (distance-time, inverse-time, and hyperbolic). Reliability was quantified using typical error (TE), coefficient of variation (CV), intraclass correlation coefficients (ICCs), and systematic differences. RESULTS: No systematic differences were observed between test and retest (P > 0.05). CS demonstrated excellent reliability across models (ICCs 0.985-0.992; TEs 0.8-1.1%; CVs 0.7-1.0%), whereas D' exhibited greater variability (TEs 11.1-13.9%; CVs 9.3-10.9%) and moderate (hyperbolic model; ICC 0.692) to good (distance-time and inverse-time models; ICCs 0.783-0.813) reliability, with 95% confidence intervals spanning poor to excellent. CONCLUSION: CS derived from severe-intensity constant-speed TTE trials under controlled laboratory conditions represents a highly reliable performance threshold, such that relatively modest intervention- or condition-induced changes are likely to be detected. The greater variability observed in D' indicates its higher sensitivity to model selection and inherent performance fluctuations during TTE trials. Therefore, caution is warranted when using D' to monitor small performance changes or evaluate intervention effects in well-trained runners.
Read CV Boqing WangECSS Paris 2023: CP-PN22
INTRODUCTION: World-class endurance athletes exhibit very high total daily energy expenditures (TDEE). To normalize these values across athletes, TDEE is often stated as a multiple of the basal metabolic rate (BMR). While across short time frames athletes may exceed 5 times the BMR, evidence suggests that the maximal amount of energy expenditure that can be sustained over extensive periods of time will asymptoticly approach ~ 2.5 times BMR (Best et al., 2025). However, longitudinal data of elite athletes is still scarce. METHODS: To investigate long-term patterns of TDEE, five internationally successful German rowers (Tier 4-5 (McKay et al., 2022); 3 female, 2 male; age 25.2 ± 3.6 years) were monitored across 992 ± 153 consecutive training days [range: 809-1,155]. All training sessions (1,769 ± 956 per athlete; range: 812-3,259) and daily sleep duration were recorded. During the monitoring period, athletes completed repeated spiroergometric step tests (9.4 ± 1.7 per athlete; range: 8-12) at irregular intervals on a rowing ergometer. Individual heart rate-V̇O2 relationships were modeled and used to estimate metabolic equivalents (MET) and exercise energy expenditure (EE) for endurance training sessions. EE of non-endurance sessions was derived using the Adult Compendium of Physical Activities (Herrmann et al., 2024). BMR was estimated using the Harris-Benedict equation (Harris & Benedict, 1918), and TDEE was expressed in relation to BMR (xBMR). EE was quantified separately for sleep, leisure, exercise, and daily total across all monitored days and training days only. The highest consecutive-day TDEE values (expressed as xBMR) were subsequently modeled over time. RESULTS: Mean TDEE amounted to 15.8 ± 3.4 MJꞏday⁻¹ [range: 12.4-19.8 MJꞏday⁻¹] across all days and 17.4 ± 3.7 MJꞏday⁻¹ [14.4-22.6 MJꞏday⁻¹] on training days. Expressed relative to BMR, average daily energy expenditure corresponded to 2.05 ± 0.16 xBMR [1.82–2.24] across all days and 2.26 ± 0.10 xBMR [2.16-2.39] on training days. Peak observed TDEE reached 28.2 ± 9.0 MJꞏday⁻¹ [18.7-41.7 MJꞏday⁻¹], corresponding to 3.64 ± 0.79 xBMR [2.75-4.85]. Exercise contributed 6.90 ± 2.07 MJꞏday⁻¹ [5.16-9.76 MJꞏday⁻¹], while leisure and sleep accounted for 8.54 ± 1.30 MJ·day⁻¹ [7.47-10.6 MJꞏday⁻¹] and 2.49 ± 0.41 MJꞏday⁻¹ [2.13-3.08 MJꞏday⁻¹], respectively. CONCLUSION: Despite prolonged high training volumes across multiple seasons, average daily energy expenditure in elite rowers remained below the proposed ~2.5 xBMR metabolic ceiling, with only transient peak values exceeding this threshold. References: McKay et al., Int J Sports Physiol Perform., 2022 Herrmann et al., J Sport Health Sci., 2024 Harris & Benedict, Proc Natl Acad Sci U S A, 1918
Read CV Ludwig RappeltECSS Paris 2023: CP-PN22
INTRODUCTION: It is well-established that low energy availability (LEA), defined as insufficient dietary energy intake relative to exercise energy expenditure, is associated with negative health and performance outcomes in physically active women. Existing research in the LEA space has historically focused on homogenous, affluent and elite athletic populations, or has not included the race/ethnicity or socioeconomic status of participants, limiting generalizability to the broader and increasingly diverse population of recreational endurance athletes. The purpose of this exploratory study was to describe the prevalence of LEA indicators (LEA-I) in a racially and ethnically, socioeconomically, and performance-level diverse cohort of female runners competing in a U.S. half-marathon. METHODS: 107 female runners aged ≥18 years competing in a U.S. half-marathon in 2025 completed pre-race surveys assessing demographics, running history, socioeconomic status, stress and recovery, and validated LEA-I screening tools (Low Energy Availability in Females Questionnaire (LEAF-Q), Eating Disorder Examination Questionnaire (EDE-Q), and self-reported history of eating disorder and/or disordered eating diagnosis). Descriptive statistics and frequency analysis were used to describe LEA-I prevalence across racial/ethnic and socioeconomic subgroups. RESULTS: 73.8% (79/107) of female runners met at least one LEA-I criteria, with 28% (30/107) meeting multiple criteria. LEA-I prevalence was high across all race/ethnic groups: Caucasian 71.4 % (15/21), African American/Black 80% (8/10), Asian American/Asian 65.5% (19/29), Latinx/Hispanic 79.5% (35/44), and Other 66.7% (2/3). Multiple LEA-I criteria were most frequently observed in Latinx/Hispanic (42% of those with LEA-I) and Asian runners (42.1%). Across income strata, runners earning <$50,000 annually demonstrated the highest prevalence of LEA-I (86.4%, 19/22) and multiple LEA-I criteria (52.6%, 10/19). LEA-I prevalence remained substantial among middle- and high-income runners, including 77.3% (17/22) in the $50,000-$84,999 group, 59.4% (19/32) in the $85,000-$150,000 group, and 77.4% (24/31) among those earning >$150,000. Elevated psychosocial stress followed a socioeconomic gradient, with higher stress observed in lower-income runners. CONCLUSION: LEA indicators are highly prevalent among female recreational-to-highly trained endurance runners across diverse racial/ethnic and socioeconomic backgrounds. These results challenge the historic assumption that LEA primarily affects white, affluent, and elite athletes, and emphasize the need for inclusive LEA screening and prevention strategies that reflect the diversity of women participating in endurance sport and exercise.
Read CV Emily LundstromECSS Paris 2023: CP-PN22