Physical performance during energy deficiency in humans: An evolutionary perspective

Energy deficiency profoundly disrupts normal endocrinology, metabolism, and physiology, resulting in an orchestrated response for energy preservation. As such, despite energy deficit is typically thought as positive for weight-loss and treatment of cardiometabolic diseases during the current obesity pandemic, in the context of contemporary sports and exercise nutrition, chronic energy deficiency is associated to negative health and athletic performance consequences. However, the evidence of energy deficit negatively affecting physical capacity and sports performance is unclear. While severe energy deficiency can negatively affect physical capacity, humans can also improve aerobic fitness and strength while facing significant energy deficit. Many athletes, also, compete at an elite and world-class level despite showing clear signs of energy deficiency. Maintenance of high physical capacity despite the suppression of energetically demanding physiological traits seems paradoxical when an evolutionary viewpoint is not considered. Humans have evolved facing intermittent periods of food scarcity in their natural habitat and are able to thrive in it. In the current perspective it is argued that when facing limited energy availability, maintenance of locomotion and physical capacity are of high priority given that they are essential for food procurement for survival in the habitat where humans evolved. When energetic resources are limited, energy may be allocated to tasks essential for survival (e.g. locomotion) while minimising energy allocation to traits that are not (e.g. growth and reproduction). The current perspective provides a model of energy allocation during energy scarcity supported by observation of physiological and metabolic responses that are congruent with this paradigm

A Comparison of the Accuracy and Reliability of the Wahoo KICKR and SRM Power Meter

The Wahoo KICKR cycling trainer is a new direct-drive electromagnetically braked bike-trainer that allows cyclists to use their own bicycles as ergometer. It is purported to provide ±3% accuracy in power, despite costing considerably less than other cycling ergometers. The purpose of this study was to assess the accuracy and reliability of several KICKR units against the more established SRM power meter using a first-principles based dynamic calibration rig (CALRIG).Five KICKRs and one SRM unit were assessed by a CALRIG-driven incremental test. Following a 15 min warm-up and ‘calibration’ as per manufacturer instructions, power was increased (starting at 50 W) by 50 W every 2 min up to 400 W. Each unit was tested twice non-consecutively, in random order. Data was recorded at 1 Hz, with the last 10 s of each stage being averaged for analysis. The mean error (%) and coefficient of determination (R2) versus CALRIG; as well as the change in mean error and Typical Error of Measurement (TEM) (expressed as a % coefficient of variation) between trials was calculated for each device.The mean error across all KICKR units was -1.5% (range: -3.1% to 0.0%) compared to -1.6% reported by the SRM. R2 >0.999 was found for all KICKR units and SRM compared to the CALRIG. The mean TEM for the KICKRs was 1.5% (range: 1.1% to 1.9%), whereas the SRM reported 0.7%. For test-retest reproducibility, two KICKRs had statistically significant changes in mean error, with an average 1.3% change across all KICKRs. Comparatively, the SRM reported a 0.4% change between trials. The Wahoo KICKR trainer measures power to a similar level of accuracy to the more reputable SRM power meter during an incremental exercise test. Although not as reproducible, the KICKR still demonstrates an acceptable level of reliability for assessing cycling performance

Mind the gap: limited knowledge of carbohydrate guidelines for competition in an international cohort of endurance athletes

Despite the well-documented role of carbohydrate (CHO) in promoting endurance exercise performance, endurance athletes typically fail to meet current recommendations in competition. Adequate nutrition knowledge is key to drive athletes' behaviour, but the current level of knowledge in this population is not known. The present study assessed knowledge of CHO for competition in an international cohort of endurance athletes using the Carbohydrates for Endurance Athletes in Competition Questionnaire (CEAC-Q). The CEAC-Q was completed by 1016 individuals (45% female), from the United Kingdom (40%), Australia/New Zealand (22%), the United States of America/Canada (18%) and other countries (21%). Total CEAC-Q scores were 50 ± 20% (mean ± sd), with no differences in scores between the five subsections (10 ± 5 points, P 2·5 h) and post-competition recovery by 28% (Low), 45% (Moderate), 48% (Moderate), and 29% (Low), respectively. Our findings indicate that endurance athletes typically have limited knowledge of carbohydrate guidelines for competition, and we identify specific knowledge gaps that can guide targeted nutrition education to improve knowledge as an initial step towards optimal dietary practice

Low energy availability: history, definition and evidence of its endocrine, metabolic and physiological effects in prospective studies in females and males

Energy availability (EA) is defined as the amount of dietary energy available to sustain physiological function after subtracting the energetic cost of exercise. Insufficient EA due to increased exercise, reduced energy intake, or a combination of both, is a potent disruptor of the endocrine milieu. As such, EA is conceived as a key etiological factor underlying a plethora of physiological dysregulations described in the female athlete triad, its male counterpart and the Relative Energy Deficiency in Sport models. Originally developed upon female-specific physiological responses, this concept has recently been extended to males, where experimental evidence is limited. The majority of data for all these models are from cross-sectional or observational studies where hypothesized chronic low energy availability (LEA) is linked to physiological maladaptation. However, the body of evidence determining causal effects of LEA on endocrine, and physiological function through prospective studies manipulating EA is comparatively small, with interventions typically lasting ≤ 5 days. Extending laboratory-based findings to the field requires recognition of the strengths and limitations of current knowledge. To aid this, this review will: (1) provide a brief historical overview of the origin of the concept in mammalian ecology through its evolution of algebraic calculations used in humans today, (2) Outline key differences from the ‘energy balance’ concept, (3) summarise and critically evaluate the effects of LEA on tissues/systems for which we now have evidence, namely: hormonal milieu, reproductive system endocrinology, bone metabolism and skeletal muscle; and finally (4) provide perspectives and suggestions for research upon identified knowledge gaps

Carbohydrate for Endurance Athletes in Competition Questionnaire (CEAC-Q): validation of a practical and time-efficient tool for knowledge assessment.

Purpose: Despite unequivocal evidence demonstrating high carbohydrate (CHO) availability improves endurance performance, athletes often report under-eating CHO during competition. Such findings may be related to a lack of knowledge though currently there are no practical or time-efficient tools to assess CHO knowledge in athletes. Accordingly, we aimed to validate a novel questionnaire to rapidly assess endurance athletes’ knowledge of competition CHO guidelines. Methods: The Carbohydrate for Endurance Athletes in Competition Questionnaire (CEAC-Q) was created by research-active practitioners, based on contemporary guidelines. The CEAC-Q comprised 25 questions divided into 5 subsections (assessing CHO metabolism, CHO loading, pre-event meal, during-competition CHO and recovery) each worth 20 points for a total possible score of 100. Results: A between-group analysis of variance compared scores in three different population groups to assess construct validity: general population (GenP; n = 68), endurance athletes (EA; n = 145), and sports dietitians/nutritionists (SDN; n = 60). Total scores were different (mean ± SD) in all pairwise comparisons of GenP (17 ± 20%), EA (46 ± 19%) and SDN (76 ± 10%, p < 0.001). Subsection scores were also significantly different between the groups, with mean subsection scores of 3.4 ± 4.7% (GenP), 9.2 ± 5.2% (EA) and 15.2 ± 3.5% (SDN, p < 0.001). Test–retest reliability of the total CEAC-Q was determined in EA (r = 0.742, p < 0.001). Conclusion: Taking ~ 10 min to complete, the CEAC-Q is a new psychometrically valid, practical and time-efficient tool for practitioners to assess athletes’ knowledge of CHO for competition and guide subsequent nutrition intervention

Reliability of resting metabolic rate between and within day measurements using the Vyntus CPX system and comparison against predictive formulas

Background: To detect longitudinal changes of resting metabolic rate (RMR) resulting from the effects of energetic stress, reliable RMR measurements are crucial. The Vyntus CPX is a new automated indirect calorimetry system for which RMR reliability has not been determined. Additionally, its agreement with common predictive RMR formulas is unknown. Aim: To determine the within and between-day reliability of RMR measurements using the Vyntus CPX system and its agreement with predictive RMR formulas. Methods: Young (31 ± 7 years) healthy participants (n = 26, 12 females, 14 males) completed three measurements of RMR, two consecutive measures on the same day, one the day before/after, all under standardised conditions. Reliability was assessed with pairwise comparisons of between-day at the same time (BDST), within day consecutive measurements (WDCM) and between-day different time (BDDT), for parameters of reliability (mean change (MC), intraclass correlation (ICC) and typical error of measurement (TEM)). Measured RMR values (kcal/day) were compared against predictive values of 4 common formulas. Results: Parameters of reliability (mean, (95% confidence interval)) were: -BDST: MC, 0.2(-2.3—2.7)% (p = 0.67); ICC, 0.92(0.84—0.97); TEM, 4.5(3.5—6.2)%. -WDCM: MC, −2.5(-6.2—1.3)% (p = 0.21); ICC, 0.88(0.74—0.88); TEM, 7.0(5.4—9.8)%. -BDDT: MC, −1.5(-4.8—1.9)% (p = 0.57); ICC, 0.90(0.76—0.95); TEM, 6.1(4.8—8.5)%. RMRratios (measured/predicted) were: 1.04 ± 0.14 (Nelson, p = 0.13), 1.03 ± 0.10 (Mifflin, p = 0.21), 0.98 ± 0.09 (Harris-benedict, p = 0.30), 0.95 ± 0.11 (Cunningham1980, p = 0.01), 1.00 ± 0.12 (Cunningham1991, p = 0.90) and 0.96 ± 0.13 (DXA, p = 0.03). Conclusions: The Vyntus CPX is reliable and measured RMR values agreed with four predictive formulas but are lower than Cunningham1980 and DXA RMR estimates for this population

The Psychological and Physiological Consequences of Low Energy Availability in a Male Combat Sport Athlete.

PURPOSE: To evaluate the effects of low energy availability (EA) on health and performance indices associated with the Male Athlete Triad and Relative Energy Deficiency in Sports (RED-S) models. METHODS: Over an 8 week period, a male combat sport athlete adhered to a phased body mass (BM) loss plan consisting of 7 weeks energy intake (EI) equating to resting metabolic rate (RMR) (1700 kcal·day) (Phase 1), 5 days of reduced EI (1200-300 kcal·day) prior to weigh-in (Phase 2) and one week of ad libitum EI post-competition (Phase 3). EA fluctuated day by day due to variations in exercise energy expenditure. Regular assessments of body composition, RMR, cardiac function, cardiorespiratory capacity, strength & power, psychological state and blood clinical chemistry for endocrine, bone turnover, hydration, electrolyte, renal, liver and lipid profiles were performed. RESULTS: BM was reduced over the 8 week period by 13.5% (72.5 to 62.7 kg). No consequences of Male Athlete Triad or RED-S were evident during phase 1, where mean daily EA equated to 20 kcal·kg·FFM·day (range: 7 to 31 kcal·kg·FFM·day) and BM and fat mass (FM) losses were 6.5 and 4.4 kg, respectively. However, consequences did present in phase 2 when mean daily EA was consistently <10 kcal·kg·FFM·day, as evidenced by alterations to endocrine hormones (e.g. testosterone: <5 nmol.L) and reduced RMR (-257 kcal·day). CONCLUSION: Data demonstrate that 7 weeks of daily fluctuations in EA equating to a mean value of 20 kcal·kg·FFM·day permits reductions of BM and FM without perturbations to physiological systems associated with the Male Athlete Triad and RED-S. In contrast, a subsequent period of 5 consecutive days of EA <10 kcal·kg·FFM·day induced consequences of Male Athlete Triad and RED-S

Prevalence of surrogate markers of relative energy deficiency in male Norwegian Olympic-level athletes

The syndrome of Relative Energy Deficiency in Sport (RED-S) includes wide-ranging effects on physiological and psychological functioning, performance, and general health. However, RED-S is understudied among male athletes at the highest performance levels. This cross-sectional study aimed to investigate surrogate RED-S markers prevalence in Norwegian male Olympic-level athletes. Athletes (N=44) aged 24.7±3.8 years, body mass 81.3±15.9kg, body fat 13.7±5.8%, and training volume 76.1±22.9 hours/month, were included. Assessed parameters included resting metabolic rate (RMR), body composition, and bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and venous blood variables (testosterone, free triiodothyronine (fT3), cortisol and lipids). Seven athletes (16%) grouped by the presence of low RMR (RMRratio <-1) was found in 16% of the athletes, all with normal RMR. Subclinical low testosterone and fT3 levels were found in nine (25%) and two (5%) athletes, respectively. Subclinical high cortisol was found in 23% of athletes while 34% had elevated LDL cholesterol levels. Seven of twelve athletes with 2 or more RED-S markers had normal RMR. In conclusion, this study found that multiple RED-S markers also exist in male Olympic-level athletes. This highlights the importance of regular screening of male elite athletes, to ensure early detection and treatment of RED-S

Patterns of energy availability of free-living athletes display day-to-day variability that is not reflected in laboratory-based protocols: Insights from elite male road cyclists

The physiological effects of low energy availability (EA) have been studied using a homogenous daily EA pattern in laboratory settings. However, whether this daily EA pattern represents those of free-living athletes and is therefore ecologically valid is unknown. To investigate this, we assessed daily exercise energy expenditure, energy intake and EA in 10 free-living elite male road cyclists (20 min Mean Maximal Power: 5.27 ± 0.25 W · kg−1) during 7 consecutive days of late pre-season training. Energy intake was measured using the remote-food photography method and exercise energy expenditure estimated from cycling crank-based power-metres. Seven-day mean ± SD energy intake and exercise energy expenditure was 57.9 ± 10.4 and 38.4 ± 8.6 kcal · kg FFM−1 · day−1, respectively. EA was 19.5 ± 9.1 kcal · kg FFM−1 · day−1. Within-participants correlation between daily energy intake and exercise energy expenditure was .62 (95% CI: .43 – .75; P < .001), and .60 (95% CI: .41 – .74; P < .001) between carbohydrate intake and exercise energy expenditure. However, energy intake only partially compensated for exercise energy expenditure, increasing 210 kcal · day−1 per 1000 kcal · day−1 increase in expenditure. EA patterns displayed marked day-to-day fluctuation (range: −22 to 76 kcal · kg FFM−1 · day−1). The validity of research using homogenous low EA patterns therefore requires further investigation

Under-Fuelling for the Work Required? Assessment of Dietary Practices and Physical Loading of Adolescent Female Soccer Players during an Intensive International Training and Game Schedule

Previous studies demonstrate that “under-fuelling” (i.e., reduced carbohydrate (CHO) and energy intake (EI) in relation to recommended guidelines) is prevalent within adult female soccer players, the consequence of which may have acute performance and chronic health implications. However, the dietary practices of adolescent female soccer players, a population who may be particularly at risk for the negative aspects of low energy availability (LEA), are not well documented. Accordingly, we aimed to quantify EI and CHO intake, physical loading and estimated energy availability (EA) in elite national team adolescent female soccer players (n = twenty-three; age, 17.9 ± 0.5 years) during a 10-day training and game schedule comprising two match days on day six (MDa) and nine (MDb). The players self-reported their EI via the remote food photography method, whilst the physical loading and associated exercise energy expenditure were assessed via GPS technology. The relative CHO intake was significantly greater (all p 6 g·kg−1) for intensive training and game schedules. These data provide further evidence for the requirement to create and deliver targeted player and stakeholder education and behaviour change interventions (especially for younger athletes) that aim to promote increased daily CHO intake in female soccer players