Gianluca Vernillo

Biomechanics and Physiology of Uphill and Downhill Running

Most running studies have considered level running (LR), yet the regulation of locomotor behaviour during uphill (UR) and downhill (DR) running is fundamental to increase our understanding of human locomotion. The purpose of this article was to review the existing literature regarding biomechanical, neuromuscular and physiological adaptations during graded running. Relative to LR, UR is characterized by a higher step frequency, increased internal mechanical work, shorter swing/aerial phase duration, and greater duty factor, while DR is characterized by increased aerial time, reduced step frequency and decreased duty factor. Grade also modifies foot strike patterns, with a progressive adoption of a mid- to fore-foot strike pattern during UR, and rear-foot strike patterns during DR. In UR, lower limb muscles perform a higher net mechanical work compared to LR and DR to increase the body’s potential energy. In DR, energy dissipation is generally prevalent compared to energy generation. The increased demands for work as running incline increases are met by an increase in power output at all joints, particularly the hip. This implies that UR requires greater muscular activity compared to LR and DR. Energy cost of running (Cr) linearly increases with positive slope but Cr of DR decreases until a minimum slope is reached at −20xa0%, after which Cr increases again. The effects of slope on biomechanics, muscle contraction patterns and physiological responses have important implications for injury prevention and success of athletes engaged in graded running competitions.

Fatigue associated with prolonged graded running

Scientific experiments on running mainly consider level running. However, the magnitude and etiology of fatigue depend on the exercise under consideration, particularly the predominant type of contraction, which differs between level, uphill, and downhill running. The purpose of this review is to comprehensively summarize the neurophysiological and biomechanical changes due to fatigue in graded running. When comparing prolonged hilly running (i.e., a combination of uphill and downhill running) to level running, it is found that (1) the general shape of the neuromuscular fatigue-exercise duration curve as well as the etiology of fatigue in knee extensor and plantar flexor muscles are similar and (2) the biomechanical consequences are also relatively comparable, suggesting that duration rather than elevation changes affects neuromuscular function and running patterns. However, ‘pure’ uphill or downhill running has several fatigue-related intrinsic features compared with the level running. Downhill running induces severe lower limb tissue damage, indirectly evidenced by massive increases in plasma creatine kinase/myoglobin concentration or inflammatory markers. In addition, low-frequency fatigue (i.e., excitation–contraction coupling failure) is systematically observed after downhill running, although it has also been found in high-intensity uphill running for different reasons. Indeed, low-frequency fatigue in downhill running is attributed to mechanical stress at the interface sarcoplasmic reticulum/T-tubule, while the inorganic phosphate accumulation probably plays a central role in intense uphill running. Other fatigue-related specificities of graded running such as strategies to minimize the deleterious effects of downhill running on muscle function, the difference of energy cost versus heat storage or muscle activity changes in downhill, level, and uphill running are also discussed.

An Extreme Mountain Ultra-Marathon Decreases the Cost of Uphill Walking and Running

Purpose: To examine the effects of the worlds most challenging mountain ultramarathon (MUM, 330 km, cumulative elevation gain of +24,000 m) on the energy cost and kinematics of different uphill gaits. Methods: Before (PRE) and immediately after (POST) the competition, 19 male athletes performed three submaximal 5-min treadmill exercise trials in a randomized order: walking at 5 km·h−1, +20%; running at 6 km·h−1, +15%; and running at 8 km·h−1, +10%. During the three trials, energy cost was assessed using an indirect calorimetry system and spatiotemporal gait parameters were acquired with a floor-level high-density photoelectric cells system. Results: The average time of the study participants to complete the MUM was 129 h 43 min 48 s (range: 107 h 29 min 24 s to 144 h 21 min 0 s). Energy costs in walking (−11.5 ± 5.5%, P < 0.001), as well as in the first (−7.2 ± 3.1%, P = 0.01) and second (−7.0 ± 3.9%, P = 0.02) running condition decreased between PRE and POST, with a reduction both in the heart rate (−11.3, −10.0, and −9.3%, respectively) and oxygen uptake only for the walking condition (−6.5%). No consistent and significant changes in the kinematics variables were detected (P-values from 0.10 to 0.96). Conclusion: Though fatigued after completing the MUM, the subjects were still able to maintain their uphill locomotion patterns noted at PRE. The decrease (improvement) in the energy costs was likely due to the prolonged and repetitive walking/running, reflecting a generic improvement in the mechanical efficiency of locomotion after ~130 h of uphill locomotion rather than constraints imposed by the activity on the musculoskeletal structure and function.

The energetics during the world’s most challenging Mountain Ultra-Marathon : a case study at the Tor des Geants®

Purpose: To provide insights into the energy requirements as well as the physiological adaptations of an experienced 50-year-old ultra-marathon male athlete during the worlds most challenging mountain ultra-marathon (MUM). Methods: The international race supporting the study was the Tor des Geants®, characterized by 330 km with +24,000 m D+ to be covered within 150 h. Before the MUM, we assessed the peak oxygen uptake (V˙O2peak) by means of an incremental graded running test. During the MUM we monitored six ascents (once per race day) with a portable gas analyzer, a GPS and a finger pulse oximeter. We then calculated the net metabolic cost per unit of distance (C), the vertical metabolic cost (Cvert) and the mechanical efficiency of locomotion (Effmech) throughout the six uphills monitored. We further monitored the distance covered, speed, altimetry and D+ from the GPS data as well as the pulse oxygen saturation with the finger pulse oximeter. Results: Subjects V˙O2peak was 48.1 mL·kg−1·min−1. Throughout the six uphills investigated the mean exercise intensity was 57.3 ± 6.0% V˙O2peak and 68.0 ± 8.7% HRpeak. C, Cvert and Effmech were 11.4 ± 1.9 J·kg−1·m−1, 57.9 ± 15.2 J·kg−1·mvert−1, and 17.7 ± 4.8%, respectively. The exercise intensity, as well as C, Cvert, and Effmech did not consistently increase during the MUM. Conclusions: For the first time, we described the feasibility of assessing the energy requirements as well as the physiological adaptations of a MUM in ecologically valid environment settings. The present case study shows that, despite the distance performed during the MUM, our participant did not experience a metabolic fatigue state. This is likely due to improvements in locomotor efficiency as the race progressed.

Bone turnover response is linked to both acute and established metabolic changes in ultra-marathon runners

Bone and energy metabolisms regulation depends on a two-way street aimed at regulating energy utilization. Mountain ultra-marathons are highly demanding aerobic performances that deeply affect the whole body homeostasis. In this study we aimed to investigate and characterize the metabolic profile (in terms of hormones involved in energy metabolism), the inflammatory adipokines, and the bone turnover; in particular the osteocalcin-mediated response has been compared in experienced mountain ultra-marathons runners versus control subjects. Serum concentrations of specific markers of bone turnover (pro-collagen type I N-terminal propeptide, carboxylated/undercarboxylated osteocalcin), measured by enzyme-linked immunosorbent assay, and metabolic hormones (C-peptide, insulin, glucagon, glucagon-like peptide, gastric-inhibitory peptide, ghrelin, leptin, resistin, and visfatin), measured by fluorescent-based multiplex assay, were compared before and after a 65u2009km mountain ultra-marathons in 17 trained runners and 12 age-matched controls characterized by a low physical activity profile. After the mountain ultra-marathons, runners experienced a reduction in pro-collagen type I N-terminal propeptide, though it remained higher than in controls; while carboxylated osteocalcin remained unchanged. Among the metabolic hormones, only glucagon and leptin were different between runners and controls at rest. C-peptide and leptin decreased after the mountain ultra-marathons in runners; while glucagon, glucagon-like peptide 1, resistin, and visfatin were all increased. Uncarboxylated osteocalcin (and uncarboxylated/carboxylated osteocalcin ratio) was decreased and this highly correlated with insulin and C-peptide levels. In conditions of high energy expenditure, homeostasis is maintained at expenses of bone metabolism. Changes in the uncarboxylated osteocalcin clearly mark the global energy needs of the body.

Mechanisms of Fatigue and Recovery in Upper versus Lower Limbs in Men.

Purpose To compare the mechanisms of fatigue and recovery between upper and lower limbs in the same subjects. Methods Twelve healthy young men performed a 2-min sustained maximal voluntary isometric contraction (MVC) of the knee extensors (KE) and on another day a 2-min MVC of the elbow flexors (EF). Neuromuscular function evaluations were performed with both transcranial magnetic and peripheral stimulations before (PRE), at the end of the 2-min MVC, and five more times within 8 min of recovery. Results Decreases in MVC and cortical voluntary activation were approximately 12% (P < 0.001) and approximately 25% greater (P = 0.04) in KE than EF at end of the 2-min MVC. Conversely, twitch response decreased approximately 29% more (P = 0.02) in EF than KE. Changes in motor-evoked potential with fatigue were not different between upper and lower limbs (P > 0.05), whereas the increase in silent period duration was approximately 30% greater in EF than KE (P < 0.05). Conclusions Upper and lower limbs presented different magnitudes of total, central and peripheral fatigue. Total neuromuscular fatigue and central fatigue were greater in KE than EF. Conversely, peripheral fatigue and corticospinal inhibition were greater in EF than KE.

Does the Running Economy Really Increase after Ultra-Marathons?

Over the years, ultra-endurance events have increasingly piqued the interest of the scientific community as they are considered an outstanding model to study the adaptive responses to both extreme loads and stresses on the human body (Millet andMillet, 2012). Notably, ultra-marathons, i.e., any event longer than the traditional marathon length of 42.195 km (Millet and Millet, 2012), have seen rising trends in participation (Hoffman et al., 2010; Cejka et al., 2014). It is well-established that endurance running speed depends on the interaction betweenmaximal oxygen uptake (V̇O2max), the ability to sustain a high percentage of V̇O2max (fractional utilization of V̇O2max), and a low economy of running (di Prampero et al., 1986). However, though the running economy (RE) is recognized to be a key determinant of running performance for “classic distances” (up to the marathon) (Saunders et al., 2004), whether or not it is also a primary determinant of ultra-marathon performances remains debated (Millet et al., 2011a, 2012b; Millet, 2012; Perrey et al., 2012). Indeed, although strategies to improve RE aremandatory in events shorter than or equal to the marathon distance, optimizing other factors associated with low-intensity endurance (e.g., minimizing damage to lower limb tissue andmuscle fatigue)may cause the runners to choose strategies that lead to a deteriorated RE in ultra-marathons (Millet et al., 2012a,b). However, although V̇O2max and its fractional utilization have been described as determinants of ultra-marathon performances (Davies and Thompson, 1986; Millet et al., 2011a), it has been argued that the greatest variance in performance (∼85%) was explained when the mean RE throughout was also added (Lazzer et al., 2012, 2014). Consequently, investigating the effects of fatigue on RE is still a crucial scientific question in ultra-marathon, both for performance optimization and a better understanding of the limits of the adaptive responses of the human body.

MiR-320a as a Potential Novel Circulating Biomarker of Arrhythmogenic CardioMyopathy

Diagnosis of Arrhythmogenic CardioMyopathy (ACM) is challenging and often late after disease onset. No circulating biomarkers are available to date. Given their involvement in several cardiovascular diseases, plasma microRNAs warranted investigation as potential non-invasive diagnostic tools in ACM. We sought to identify circulating microRNAs differentially expressed in ACM with respect to Healthy Controls (HC) and Idiopathic Ventricular Tachycardia patients (IVT), often in differential diagnosis. ACM and HC subjects were screened for plasmatic expression of 377 microRNAs and validation was performed in 36 ACM, 53 HC, 21 IVT. Variable importance in data partition was estimated through Random Forest analysis and accuracy by Receiver Operating Curves. Plasmatic miR-320a showed 0.53u2009±u20090.04 fold expression difference in ACM vs. HC (pu2009<u20090.01). A similar trend was observed when comparing ACM (nu2009=u200913) and HC (nu2009=u200917) with athletic lifestyle, a ACM precipitating factor. Importantly, ACM patients miR-320a showed 0.78u2009±u20090.05 fold expression change vs. IVT (pu2009=u20090.03). When compared to non-invasive ACM diagnostic parameters, miR-320a ranked highly in discriminating ACM vs. IVT and it increased their accuracy. Finally, miR-320a expression did not correlate with ACM severity. Our data suggest that miR-320a may be considered a novel potential biomarker of ACM, specifically useful in ACM vs. IVT differentiation.

Effect of repeated-sprints on the reliability of short-term parasympathetic reactivation

This study determined the reliability of post-exercise heart rate recovery (HRR) and vagal-related HR variability (HRV) after repeated-sprints (RSs), and contrasted it with the smallest worthwhile change (SWC) of these indices. Fourteen healthy male participants performed on four occasions, separated by 7 days, five 30-m sprints interspersed by 25-s of recovery. Post-exercise HR during 10 min of seated rest was measured. HRR during the first 60-s of recovery was computed (HRR60s). HRV indices were calculated in time and frequency domains during the last 5-min of the recovery. Absolute and relative reliability were assessed by typical error of measurement expressed as coefficient of variation (CV) and intraclass correlation coefficients (ICCs), respectively. Sensitivity was assessed comparing SWC to the typical error of measurement. CV ranged from 3.6% to 13.5% and from 6.3% to 109.2% for the HRR and HRV indices, respectively. ICCs were from 0.78 to 0.96 and from 0.76 to 0.92, respectively. HRR and HRV indices showed large discrepancies reliability. HRR60s and the square root of the mean sum of the squared differences between R-R intervals presented the highest levels of both absolute and relative reliability. However, SWC was lower than the typical error of measurement, indicating insufficient sensitivity to confidently detect small, but meaningful, changes in HRR and HRV indices.

Postexercise autonomic function after repeated-sprints training

PurposeWe examined the effects of an 8-week repeated-sprint (RS) training protocol on postexercise parasympathetic reactivation (PNSr) in healthy adults.MethodsEighteen male adults (24.3xa0±xa03.7xa0years) were assigned to either of two groups. One group (nxa0=xa09) performed RS training (EXP, 3 timesxa0week−1, 18 maximal all-out 15-m sprints interspersed with 17xa0s of passive recovery); the other served as the control group (CON, nxa0=xa09). Performance before, during, and after was assessed by measuring RS ability time (Sdec) and total sprint time. The subjects were then seated for 10xa0min immediately after each trial and postexercise HR recovery (HRR), and vagal-related HR variability (HRV) indices were measured.ResultsAll subjects demonstrated a decrease in Sdec. However, only EXP showed a decrease in total sprint time (−10.5xa0% of baseline value). Using a qualitative statistical analysis method, we found a likely to almost certain positive effect of RS training on HR. The mean of each HRR and HRV index indicated a greater change in PNSr in EXP than in CON (e.g. with a 78/22/1xa0% chance to demonstrate a positive/trivial/negative effect on HRR60s after RS training; 74/21/5xa0% on LN rMSSD5–10min). Large correlations were noted between the changes in Sdec [rxa0=xa00.59, 90xa0% CI (0.43)], total sprint time [rxa0=xa0−0.61 (0.42)] and HRR60s.ConclusionRS training seems to be an effective method to improve postexercise PNSr in healthy adults. Also, HRR60s appears to be a method for evaluating positive adaption to RS training.