The Association of Fatigue With Decreasing Regularity of Locomotion During an Incremental Test in Trained and Untrained Healthy Adults

Fatigue is a key factor that affects human motion and modulates physiology, biochemistry, and performance. Prolonged cyclic human movements (locomotion primarily) are characterized by a regular pattern, and this extended activity can induce fatigue. However, the relationship between fatigue and regularity has not yet been extensively studied. Wearable sensor methodologies can be used to monitor regularity during standardized treadmill tests (e.g., the widely used Bruce test) and to verify the effects of fatigue on locomotion regularity. Our study on 50 healthy adults [27 males and 23 females; <40 years; five dropouts; and 22 trained (T) and 23 untrained (U) subjects] showed how locomotion regularity follows a parabolic profile during the incremental test, without exception. At the beginning of the trial, increased walking speed in the absence of fatigue is associated with increased regularity (regularity index, RI, a. u., null/unity value for aperiodic/periodic patterns) up until a peak value (RI = 0.909 after 13.8 min for T and RI = 0.915 after 13.4 min for U subjects; median values, n. s.) and which is then generally followed (after 2.8 and 2.5 min, respectively, for T/U, n. s.) by the walk-to-run transition (at 12.1 min for both T and U, n. s.). Regularity then decreases with increased speed/slope/fatigue. The effect of being trained was associated with significantly higher initial regularity [0.845 (T) vs 0.810 (U), p < 0.05 corrected], longer test endurance [23.0 min (T) vs 18.6 min (U)], and prolonged decay of locomotor regularity [8.6 min (T) vs 6.5 min (U)]. In conclusion, the monitoring of locomotion regularity can be applied to the Bruce test, resulting in a consistent time profile. There is evidence of a progressive decrease in regularity following the walk-to-run transition, and these features unveil significant differences among healthy trained and untrained adult subjects

Cardiac autonomic modulations and psychological correlates in the Yukon Arctic Ultra : the longest and the coldest ultramarathon

Studies on human physical performance in extreme environments have effectively approached the investigation of adaptation mechanisms and their physiological limits. As scientific interest in the interplay between physiological and psychological aspects of performance is growing, we aimed to investigate cardiac autonomic control, by means of heart rate variability, and psychological correlates, in competitors of a subarctic ultramarathon, taking place over a 690 km course (temperatures between +5 and -47\uc2\ub0C). At baseline (PRE), after 277 km (D1), 383 km (D2), and post-race (POST, 690 km), heart rate (HR) recordings (supine, 15 min), psychometric measurements (Profile of Mood States/POMS, Borg fatigue, and Karolinska Sleepiness Scale scores both upon arrival and departure) were obtained in 16 competitors (12 men, 4 women, 38.6 \uc2\ub1 9.5 years). As not all participants reached the finish line, comparison of finishers (FIN, n = 10) and non-finishers (NON, n = 6), allowed differential assessment of performance. Resting HR increased overall significantly at D1 (FIN +15.9; NON +14.0 bpm), due to a significant decrease in parasympathetic drive. This decrease was in FIN only partially recovered toward POST. In FIN only, baseline HR was negatively correlated with mean velocity [r -0.63 (P.04)] and parasympathetic drive [pNN50+: r -0.67 (P.03)], a lower HR and a higher vagal tone predicting a better performance. Moreover, in FIN, a persistent increase of the long-term self-similarity coefficient, assessed by detrended fluctuation analysis (DFAa2 was retrieved, possibly due to higher alertness. As for psychometrics, at D1, POMS Vigor decreased (FIN: -7.0; NON: -3.8), while Fatigue augmented (FIN: +6.9; NON: +5.0). Sleepiness increased only in NON, while Borg scales did not exhibit changes. Baseline comparison of mood states with normative data for athletes displayed significantly higher positive mood in our athletes. Results show that: the race conditions induced early decreases in parasympathetic drive; the extent of vagal withdrawal, associated to the timing of its recovery, is crucial for success; pre-competition lower resting HR predicts a better performance; psychological profile is reliably depicted by POMS, but not by Borg fatigue scales. Therefore, assessment of heart rate variability and psychological profile may monitor and partly predict performance in long-duration ultramarathon in extreme cold environment

Negative Energy Balance Does Not Alter Fat-Free Mass During the Yukon Arctic Ultra—The Longest and the Coldest Ultramarathon

Purpose: The objective of this study was to determine alterations in caloric balance, body composition, metabolites, and cytokines in athletes participating in the Yukon Arctic Ultra.Methods: Ten participants traveling on foot in the 2017 692-km event were recruited for the study. Measurements and samples were obtained at pre-event, 278 km (C1), 384 km (C2), and post-event. Body composition measurements were obtained using bioelectrical impedance analysis. Accelerometer devices were utilized to provide an estimation of caloric expenditure and dietary recalls provided assessments of caloric intake. Blood serum samples were collected, processed, and analyzed using enzyme-linked immunosorbent assays or nuclear magnetic resonance. Results were analyzed using linear mixed model, presented as means ± SD, and considered significant at p < 0.05.Results: Participants (8 males, 2 females; age: 37 ± 10 years; body mass index: 24.4 ± 2.5 kg/m2) were recruited. Four males and one female completed the entire event in 260 ± 19 h. Caloric intake/expenditure was 4,126 ± 1,115 kcal/day and 6,387 ± 781 kcal/day, respectively, indicating a caloric deficit of 2,261 ± 1,543 kcal/day. Total mass, body mass index, and fat mass were reduced at each time point of the event. Fat-free mass (FFM) was unchanged throughout the event. Follistatin was increased at C1 (1,715 ± 876 pg/ml) in comparison to baseline. Acetoacetate increased significantly at post-event (6.1 ± 1.5 mg/ml).Conclusions: Despite a pronounced caloric deficit and sustained activity under extreme cold conditions, FFM was preserved with an increase in serum follistatin and acetoacetate. Future studies should be directed at the role of nutrient strategies and/or training methods on the retention of FFM under these conditions

SERUM MYOKINE LEVELS DURING THE 430 MILE YUKON ARCTIC ULTRA

A. N. Weaver1, M. S. Coker1, M. Steinach2, R. H. Coker1 1Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, 2Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany This research was presented by representatives from the Alaska chapter of the American College of Sports Medicine. PURPOSE: The Yukon Arctic Ultra is considered the longest and coldest ultraendurance event in the world. Recently, cold exposure and exercise have been reported to influence circulating levels of certain myokines and proteins that may influence the “browning” of white adipose tissue. The purpose of the study was to evaluate the influence of the Yukon Arctic Ultra (430 mile participants) on serum irisin, meteorin, IL-6, and FGF21 in healthy individuals. METHODS: Eight male and female participants (mean±SEM; age = 44±3 yr; BMI = 23.3±0.9) were recruited for participation. Blood samples were collected at pre-event, mid event (200 mile) and post-event checkpoints. RESULTS: The average temperature during the event ranged from -45ºC to -8ºC. Due to the challenging conditions, only 50% of the participants finished the event and they lost 2.2±0.3 kg of body weight. Serum irisin was 307±63 ug/ml (pre-event), rose to 496±17 ug/ml (mid-event), and remained elevated at 513±18 (post-event) but the lack of significance was likely due to attrition. Serum meteorin remained stable at 3.1±0.1 ng/ml (pre-event), 3.1±0.0 (mid-event), and 3.0±0.1 ng/ml (post-event). Serum IL-6 fell from 183±51 ug/ml (pre-event), to 118±55 ug/ml (mid-event), to 90±39 ug/ml (post-event). Serum FGF21 was 30±3 ug/ml (pre-event), 34±8 ug/ml (mid-event), and 62±21 ug/ml (post-event). CONCLUSION: The combined influence of cold exposure and extreme levels of prolonged ultraendurance exercise may promote elevations in serum irisin and FGF21, while IL-6 may decline under these circumstances. Despite previous reports in pre-clinical studies of cold exposure induced increments in serum meteorin, these responses were not evident in a limited number of humans undergoing substantially greater metabolic stress. Utilizing participants competing in all distances of Yukon Arctic Ultra 2016 and hot-weather marathons, future studies are planned to gather more data on serum myokines, and examine potential changes in FNDC5 and PGC-1α in muscle and UCP-1 gene expression in white adipose tissue

A Fluid Shift for Endurance Exercise - Why Hydration Matters

As modern-day humans, we still bear the genetic heritage of our ancestors who evolved under conditions very different from today and who were selected for a great amount of daily physical exercise.1 We should be aware of this two-million-year-old heritage 2 and include physical exercise in our everyday lives to prevent civilization-induced disorders, as for example metabolic syndrome and cardiovascular diseases,3 and to stay physically and mentally fit.4 Indeed, regular endurance training has many beneficial consequences such as improved cardiovascular function, lower morbidity, and mortality rates and overall improved physical fitness.5-7 Moreover, exercise training may even reverse pathological changes associated with diseases of civilization

PHYSIOLOGICAL CHANGES IN PARTICIPANTS OF AN ULTRAMARATHON IN SUBARCTIC CLIMATE

Introduction The Yukon Arctic Ultra (YAU) is an ultramarathon in the Yukon-Territory of Canada taking place during February. We assessed changes in participants entering the 690km footrace and evaluated energy expenditure (EE), energy intake (EI), energy deficit (ED), body weight (BW) and composition (fat mass FM, fat-free mass FFM), sleep parameters (sleep time ST, REM-sleep RS, deep-sleep DS) and heart rate variability HRV (pNN50 and lowfrequency to high-frequency ratio LF/HF). We hypothesized that high levels of physical exertion in the extremely cold environment would lead to changes in these parameters. Material & Methods N=4 of n=6 volunteers finished and were included in the analysis. BW, FM, FFM were measured using a scale and the bio-impedance-analysis. EI, ED were estimated using food protocols. EE, ST were measured using the SenseWear-actimeter continuously and RS and DS using the Zeo-Sleep-device at distinctive nights. HRV (pNN50, LF/HF) was evaluated using the Polar-monitor RS800CX and beat-to-beat analysis. Resulting data were statistically analyzed using respective statistical software. Results The evaluation revealed high rates of daily EE (an average of 4.5 MET/d with peak values of 38,000 kJ/d). We also found a considerable ED: only 44% of the EE was covered by EI (p<0.001). Considerable changes in BW, FM, FFM occurred: participants lost an average 6.2 kg of BW (p<0.001) with a maximum loss of 7.9 kg. Regarding body composition, there was an initial loss in FM (p<0.001) and in progression a loss in FFM (p=0.052). The average FM loss was 3.9 kg and 2.3 kg in FFM (=27.9% from starting-FM, 3.4% from starting-FFM). We found a sleep deficit at the start and end of the race; however, ST decreases were not significant (p=0.05). There were changes in the sleep phases: a decrease in RS after the beginning (p=0.005) and increase in DS after the end of the race (p=0.386). Analysis of HRV revealed a decrease in the pNN50 (p=0.429) and a significant decrease in the LF/HF (p=0.035). Discussion & Conclusions Participation in the YAU leads to extensive increases in EE, ED; decreases in BW, FM, FFM; decreases in ST and changes in sleep-phases. We found decreases in pNN50 and LF/HF-ratio indicating an increase of rhythms predominantly influenced by the parasympathetic nervous system

Can skin temperature recordings predict GLOC?

Background: Modern aerial combat manouevres are an enormous challenge for human physiology [1,2].To predict the probability of a g- force induced loss of consciousness (GLOC) has been subject of numerous studies. Changes in perfusion (NIRS) and/or function of the brain (EEG, evoked potentials) have been the primary focus searching a predictor while centrifugal reallocation of blood volume is the primary cause for this blackout.To determine the peripheral bloodflow skin temperature might be used [3]. We present a pilot study using fast measurements of peripheral temperatures to predict this peripheral pooling effect. Material & Methods: 9 of the 20 subjects suffered an almost loss of consciousness (ALOC). Peripheral temperatures tended to be higher in subjects with an almost blackout.The strongest effect regarding the difference of the two groups was recorded at the upper arm (p<0.05). 20 healthy subjects were tested using a combined lower body negative pressur/tilt table.The produced push-pull effect has been used to select pilots suited to fly a forth generation jet fighter. The complete procedure was split in two phases before, one phase during and one phase after the induced push-pull effect. Recording skin III temperatures proximal and distal of the upper and lower limbs allowed to quantify the effect of a peripheral perfusion change. Results & Discussion: The probability of ALOC in this experiment could be predicted recording peripheral temperatures. Higher peripheral temperatures before the push-pull phase might be an indicator for peripheral vasodilation or a lowered sympathetic activation [4]. However, to verify this effect, the experiment has to be repeated using more subjects and different hyper-g scenarios as the short and long arm centrifuge and real aircraft manoeuvres. References: 1. Hanousek, J, P Dosel, J Cmiral, and J Petricek. "Physiological Response of Pilots to the Load of Lower Body Negative Pressure." J Gravit Physiol 4, no. 2 (1997): P33-4 2. Dosel, P, J Hanousek, J Cmiral, and J Petricek. "Physiological Response of Pilots to the LBNP-, Flight-, and Centrifuge Load." J Gravit Physiol 5, no. 1 (1998): P41-2 3. Rubinstein, E H, and D I Sessler. "Skin-surface Temperature Gradients Correlate with Fingertip Blood Flow in Humans." Anesthesiology 73, no. 3 (1990): 541-5 4. Charkoudian, Nisha. "Skin Blood Flow in Adult Human Thermoregulation: How It Works, When It Does Not, and Why." Mayo Clinic proceedings. Mayo Clinic 78, no. 5 (2003): doi:10.4065/78.5.60