Reliability and Validity of Predicted Performance in the Severe-Intensity Domain From the 3-Minute All-Out Running Test.

PURPOSE: The aim of this study was to analyze the reliability and validity of the predicted distance-time relationship in the severe-intensity domain from a 3-minute all-out running test (3MT). METHODS: Twelve runners performed two 3MTs (test #1 and test #2) on an outdoor 400-m track after familiarization. Eighteen-hertz Global Positioning System data were used to estimate critical speed (CS) and distance covered above CS (D'). Time to cover 1200 and 3600 m (T1200 and T3600, respectively) was predicted using CS and D' estimates from each 3MT. Eight runners performed 2 time trials in a single visit to assess real T1200 and T3600. Intraclass correlation coefficients (ICCs) and standard errors of measurement were calculated for reliability analysis. RESULTS: Good to excellent reliability was found for CS, T1200, and T3600 estimates from 3MT (ICC > .95, standard error of measurement between 1.3% and 2.2%), and poor reliability was found for D' (ICC = .55, standard error of measurement = 27%). Predictions from 3MT were significantly correlated to actual T1200 (r = .87 and .85 for test #1 and test #2, respectively) and T3600 (r = .91 and .82 for test #1 and test #2, respectively). The calculation of error prediction showed a systematic error between predicted and real T3600 (6.4% and 7.8% for test #1 and test #2, respectively, P < .01) contrary to T1200 (P > .1). Random error was between 4.4% and 6.1% for both distances. CONCLUSIONS: Despite low reliability of D', 3MT yielded a reliable predicted distance-time relationship allowing repeated measures to evidence change with training adaptation. However, caution should be taken with prediction of performance potential of a single individual because of substantial random error and significant underestimation of T3600.

Elite vs. Experienced Male and Female Trail Runners: Comparing Running Economy, Biomechanics, Strength, and Power.

ABSTRACT: Besson, T, Pastor, FS, Varesco, G, Berthet, M, Kennouche, D, Dandrieux, P-E, Rossi, J, and Millet, GY. Elite vs. experienced male and female trail runners: comparing running economy, biomechanics, strength, and power. J Strength Cond Res 37(7): 1470-1478, 2023-The increased participation in trail running (TR) races and the emergence of official international races have increased the performance level of the world best trail runners. The aim of this study was to compare cost of running (Cr) and biomechanical and neuromuscular characteristics of elite trail runners with their lower level counterparts. Twenty elite (10 females; ELITE) and 21 experienced (10 females; EXP) trail runners participated in the study. Cr and running biomechanics were measured at 10 and 14 km·h-1 on flat and at 10 km·h-1 with 10% uphill incline. Subjects also performed maximal isometric voluntary contractions of knee and hip extensors and knee flexors and maximal sprints on a cycle ergometer to assess the power-torque-velocity profile (PTVP). Athletes also reported their training volume during the previous year. Despite no differences in biomechanics, ELITE had a lower Cr than EXP (p < 0.05). Despite nonsignificant difference in maximal lower-limb power between groups, ELITE displayed a greater relative torque (p < 0.01) and lower maximal velocity (p < 0.01) in the PTVP. Females displayed shorter contact times (p < 0.01) compared with males, but no sex differences were observed in Cr (p > 0.05). No sex differences existed for the PTVP slope, whereas females exhibited lower relative torque (p < 0.01) and velocity capacities (p < 0.01) compared with males. Although not comprehensively assessing all determining factors of TR performance, those data evidenced level and sex specificities of trail runners in some factors of performance. Strength training can be suggested to lower level trail runners to improve Cr and thus TR performance.

VO2max and Velocity at VO2max Play a Role in Ultradistance Trail-Running Performance.

PURPOSE: Previous research has shown that maximal oxygen uptake (VO2max) significantly influences performance in trail-running races up to 120 km but not beyond. Similarly, the influence of running economy on performance in ultratrail remains unclear. The aim of our study was, therefore, to determine the physiological predictors of performance in a 166-km trail-running race. METHODS: Thirty-three experienced trail runners visited the laboratory 4 to 8 weeks before the race to undergo physiological testing including an incremental treadmill test and strength assessments. Correlations and regression analyses were used to determine the physiological variables related to performance. RESULTS: Average finishing time was 37:33 (5:52) hours. Performance correlated significantly with VO2max (r = -.724, P < .001), velocity at VO2max (r = -.813, P < .001), lactate turn point expressed as percentage of VO2max (r = -.510, P = .018), cost of running (r = -.560, P = .008), and body fat percentage (r = .527, P = .012) but was not related to isometric strength. Regression analysis showed that velocity at VO2max predicted 65% of the variability in performance (P < .001), while a model combining VO2max and cost of running combined predicted 62% of the variability (P = .008). CONCLUSION: This is the first study to show that VO2max and velocity at VO2max are significant predictors of performance in a 166-km trail-running race. This suggests that ultratrail runners should focus on the development of these 2 qualities to optimize their race performance.

Changes in Cost of Locomotion Are Higher after Endurance Cycling Than Running When Matched for Intensity and Duration.

INTRODUCTION: Cost of locomotion (C L ) has been shown to increase after endurance running and cycling bouts. The main purpose of this study was to compare, in the same participants, the effect of both modalities on C L when matched for relative intensity and duration. METHODS: Seventeen recreational athletes performed two incremental tests in running and cycling to determine the first ventilatory threshold then two 3-h bouts of exercise at 105% of threshold, with gas exchange measurements taken for 10 min at the start, middle and end of the 3 h to calculate C L . Neuromuscular fatigue during isometric knee extensor contractions and force-velocity profile on a cycle ergometer were assessed before and immediately after the 3-h trials. RESULTS: C L significantly increased at mid (+3.7%, P = 0.006) and end (+7.4%, P < 0.001) of exercise for cycling compared with start, whereas it did not change with time for running. Cardio-respiratory and metabolic variables changed similarly for cycling and running, therefore not explaining the time-course differences in C L between modalities. Changes in C L during cycling correlated significantly with loss of maximal force extrapolated from the force-velocity profile ( r = 0.637, P = 0.006) and changes in cadence ( r = 0.784, P < 0.001). CONCLUSIONS: The type of locomotion influences the effects of exercise on energy cost because 3 h of exercise at the same relative intensity caused a significant increase of cycling C L , and no changes in running C L . The changes in C L in cycling are likely due, at least in part, to fatigue in the locomotor muscles.

Elite Road vs. Trail Runners: Comparing Economy, Biomechanics, Strength, and Power.

ABSTRACT: Sabater Pastor, FS, Besson, T, Berthet, M, Varesco, G, Kennouche, D, Dandrieux, P-E, Rossi, J, and Millet, GY. Elite road vs. trail runners: comparing economy, biomechanics, strength, and power. J Strength Cond Res 37(1): 181-186, 2023-The purpose of this study was to determine the differences between road (ROAD) vs. trail (TRAIL) elite runners in terms of force-velocity profile (FVP), running biomechanics, lower-limb maximal isometric strength, cost of running (Cr), and training. Seventeen male elite athletes (10 TRAIL and 7 ROAD) participated in this study. Force-velocity profile was measured using a 2-sprint test on a cycle ergometer. Strength was assessed with a dynamometer measuring isometric maximum voluntary torque of the knee extensors and knee flexors. Biomechanics parameters (running kinematics and stiffness) were measured, and Cr was calculated at 10 and 14 km·h-1 at 0% slope and at 10 km·h-1 on a 10% slope on a treadmill. Athletes also reported their training duration during the previous year. Theoretical maximal torque (F0) and maximal power (Pmax) in the FVP were higher for TRAIL vs. ROAD (122 ± 13 vs. 99 ± 7 N·m, p = 0.001; and 726 ± 89 vs. 626 ± 44 W; p = 0.016). Cost of running was higher for TRAIL compared with ROAD on flat at 14 km·h-1 (4.32 ± 0.22 vs. 4.06 ± 0.29 J·kg-1·m-1; p = 0.047) but similar at 10 km·h-1 and uphill. No differences were found in maximal isometric strength or running biomechanics. ROAD spent 81% more time training than TRAIL (p = 0.0003). The specific training (i.e., "natural" resistance training) performed during graded running in trail runners and training on level surface at high speed may explain our results. Alternatively, it is possible that trail running selects stronger athletes because of the greater strength requirements of graded running.

Power Output Manipulation from Below to Above the Gas Exchange Threshold Results in Exacerbated Performance Fatigability.

INTRODUCTION: Performance fatigability is substantially greater when exercising in the severe- versus heavy-intensity domain. However, the relevance of the boundary between moderate- and heavy-intensity exercise, the gas exchange threshold (GET), to performance fatigability is unclear. This study compared alterations in neuromuscular function during work-matched exercise above and below the GET. METHODS: Seventeen male participants completed work-matched cycling for 90, 110, and 140 min at 110%, 90%, and 70% of the GET, respectively. Knee extensor isometric maximal voluntary contraction (MVC), high-frequency doublets (Db100), low- to high-frequency doublet ratio (Db10:100), and voluntary activation were measured at baseline, 25%, 50%, 75%, and 100% of task completion. During the initial baseline visit and after each constant work rate bout, ramp-incremental exercise was performed, and peak power output and oxygen uptake (V̇O 2peak ) were determined. RESULTS: After the 70% and 90% GET trials, similar reductions in MVC (-14% ± 6% and -14% ± 8%, respectively, P = 0.175) and Db100 (-7% ± 9% and -6% ± 9%, respectively, P = 0.431) were observed. However, for a given amount of work completed, reductions in MVC (-25% ± 15%, P = 0.008) and Db100 (-12% ± 8%, P = 0.029) were up to 2.6-fold greater during the 110% than the 90% GET trial. Peak power output and V̇O 2peak during ramp-incremental exercise were reduced by 7.0% ± 11.3% and 6.5% ± 9.3%, respectively, after the 110% GET trial relative to the baseline ramp ( P ≤ 0.015), with no changes after the moderate-intensity trials ( P ≥ 0.078). CONCLUSIONS: The lack of difference in fatigability between the trials at 70% and 90% GET, coupled with the greater fatigability at 110% relative to 90% GET, shows that exceeding the moderate- to heavy-intensity boundary has implications for performance fatigability, while also impairing maximal exercise performance capacity.

Performance Determinants in Trail-Running Races of Different Distances.

PURPOSE: While the physiological determinants of road running have been widely studied, there is a lack of research in trail-running racing performance. The aim of our study was to determine the physiological predictors of trail-running performance in races of different distances in similar terrain and weather conditions. METHODS: Seventy-five trail runners participating in one of the races of the Ultra-Trail du Mont-Blanc were recruited. Previous to the race, each runner was evaluated with (1) an incremental treadmill test to determine maximal oxygen uptake, ventilatory thresholds, cost of running, and substrate utilization; (2) a power-force-velocity profile on a cycle ergometer; (3) maximal voluntary contractions of the knee extensors and plantar flexors; and (4) anthropometric characteristics. Neuromuscular fatigue was evaluated after the races. Twenty-four runners finished a SHORT (<55 km), 16 finished a MEDIUM (101 km), and 14 finished a LONG (>145 km) race. Correlations and multiple linear regressions were used to find the determinants of performance in each race distance. RESULTS: Performance in SHORT was explained by maximal oxygen uptake and lipid utilization at 10 km/h (r2 = .825, P < .001). Performance in MEDIUM was determined by maximal oxygen uptake, maximal isometric strength, and body fat percentage (r2 = .917, P < .001). A linear model could not be applied in LONG, but performance was correlated to peak velocity during the incremental test. CONCLUSIONS: Performance in trail running is mainly predicted by aerobic capacity, while lipid utilization also influences performance in races <60 km and performance in approximately 100 km is influenced by muscle strength and body composition.

Disparate Mechanisms of Fatigability in Response to Prolonged Running versus Cycling of Matched Intensity and Duration.

INTRODUCTION: Running and cycling represent two of the most common forms of endurance exercise. However, a direct comparison of the neuromuscular consequences of these two modalities after prolonged exercise has never been made. The aim of this study was to compare the alterations in neuromuscular function induced by matched-intensity and duration cycling and running exercise. METHODS: During separate visits, 17 endurance-trained male participants performed 3 h of cycling and running at 105% of the gas exchange threshold. Neuromuscular assessments were taken are preexercise, midexercise, and postexercise, including knee extensor maximal voluntary contractions (MVC), voluntary activation (VA), high- and low-frequency doublets (Db100 and Db10, respectively), potentiated twitches (Qtw,pot), motor evoked potentials (MEP), and thoracic motor evoked potentials (TMEP). RESULTS: After exercise, MVC was similarly reduced by ~25% after both running and cycling. However, reductions in VA were greater after running (-16% ± 10%) than cycling (-10% ± 5%; P < 0.05). Similarly, reductions in TMEP were greater after running (-78% ± 24%) than cycling (-15% ± 60%; P = 0.01). In contrast, reductions in Db100 (running vs cycling, -6% ± 21% vs -13% ± 6%) and Db10:100 (running vs cycling, -6% ± 16% vs -19% ± 13%) were greater for cycling than running (P ≤ 0.04). CONCLUSIONS: Despite similar decrements in the knee extensor MVC after running and cycling, the mechanisms responsible for force loss differed. Running-based endurance exercise is associated with greater impairments in nervous system function, particularly at the spinal level, whereas cycling-based exercise elicits greater impairments in contractile function. Differences in the mechanical and metabolic demands imposed on the quadriceps could explain the disparate mechanisms of neuromuscular impairment after these two exercise modalities.

Effect of ground technicity on cardio-respiratory and biomechanical parameters in uphill trail running.

The goal of this study was to analyse the effects of ground technicity on cardio-respiratory and biomechanical responses during uphill running. Ten experienced male trail-runners ran ∼10.5 min at racing pace on two trails with different (high and low) a priori technicity levels. These two runs were replicated (same slope, velocity, and distance) indoor on a motor-driven treadmill. Oxygen uptake, minute ventilation (V̇E), heart rate as well as step frequency and medio-lateral feet accelerations (i.e. objective indices of uneven terrain running patterns adjustments) were continuously measured throughout all sessions. Rating of perceived exertion (RPE) and perceived technicity were assessed at the end of each bout. Oxygen cost of running (O2Cr) (+10.5%; p < 0.001), V̇E (+21%; p < 0.004) and the range and variability of feet medio-lateral accelerations (+116% and +134%, respectively; p < 0.001), were significantly greater when running on trail compared to the treadmill, regardless of the a priori technicity level. Despite perceived technicity being lower on treadmill (p < 0.001), RPE was not different between trail and treadmill runs (p < 0.68). It is concluded that running uphill on a trail vs. a treadmill significantly elevates both O2Cr and magnitude/variability of feet medio-lateral accelerations but no difference could be identified between trails of different a priori technicities. These results strengthen the need for trainers and race organisers to consider terrain technicity per se as a challenging cardio-respiratory and biomechanical component in uphill trail running.Highlights Ten experienced male trail-runners ran ∼10.5 min at racing pace on two trails with different a priori technicity levels. The two runs were replicated (same slope, velocity, and distance) indoor on a motor-driven treadmill.Oxygen cost of running (O2Cr), minute ventilation (V̇E) as well as medio-lateral feet accelerations (i.e. objective indices of uneven terrain running patterns adjustments) were continuously measured throughout all sessions. Rating of perceived exertion (RPE) and perceived technicity were assessed at the end of each bout.O2Cr (+10.5%; p < 0.001), V̇E (+21%; p < 0.004) and the magnitude and variability of feet medio-lateral accelerations (+116% and +134%, respectively; p < 0.001) were significantly greater when running on trail compared to treadmill, regardless of the a priori technicity level. Despite O2Cr being different between trail and treadmill runs, RPE was not.Thus, running uphill on a trail vs. on a treadmill significantly elevates both O2Cr and magnitude/variability of feet medio-lateral accelerations but no difference could be identified between trails of different a priori technicities.

Sex Differences in Neuromuscular Fatigue and Changes in Cost of Running after Mountain Trail Races of Various Distances.

INTRODUCTION: Women have been shown to experience less neuromuscular fatigue than men in knee extensors (KE) and less peripheral fatigue in plantar flexors (PF) after ultratrail running, but it is unknown if these differences exist for shorter trail running races and whether this may impact running economy. The purpose of this study was to characterize sex differences in fatigability over a range of running distances and to examine possible differences in the postrace alteration of the cost of running (Cr). METHODS: Eighteen pairs of men and women were matched by performance after completing different races ranging from 40 to 171 km, divided into SHORT versus LONG races (<60 and >100 km, respectively). Neuromuscular function and Cr were tested before and after each race. Neuromuscular function was evaluated on both KE and PF with voluntary and evoked contractions using electrical nerve (KE and PF) and transcranial magnetic (KE) stimulation. Oxygen uptake, respiratory exchange ratio, and ventilation were measured on a treadmill and used to calculate Cr. RESULTS: Compared with men, women displayed a smaller decrease in maximal strength in KE (-36% vs -27%, respectively, P < 0.01), independent of race distance. In SHORT only, women displayed less peripheral fatigue in PF compared with men (Δ peak twitch: -10% vs -24%, respectively, P < 0.05). Cr increased similarly in men and women. CONCLUSIONS: Women experience less neuromuscular fatigue than men after both "classic" and "extreme" prolonged running exercises but this does not impact the degradation of the energy Cr.

Degradation of energy cost with fatigue induced by trail running: effect of distance.

PURPOSE: The effect of trail running competitions on cost of running (Cr) remains unclear and no study has directly examined the effect of distances in similar conditions on Cr. Accordingly, the aims of this study were to (i) assess the effect of trail running races of 40-170 km on Cr and (ii) to assess whether the incline at which Cr is measured influences changes in Cr. METHODS: Twenty trail runners completed races of < 100 km (SHORT) and 26 trail runners completed races of > 100 km (LONG) on similar courses and environmental conditions. Oxygen uptake, respiratory exchange ratio, ventilation, and blood lactate were measured before and after the events on a treadmill with 0% (FLAT) and 15% incline (UH) and Cr was calculated. RESULTS: Cr increased significantly after SHORT but not LONG races. There was no clear relationship between changes in Cr and changes in ventilation or blood lactate. There was a significant correlation (r = 0.75, p < 0.01) between changes in FLAT and UH Cr, and the change in Cr was not affected by the incline at which Cr was measured. CONCLUSION: The distance of the trail running race, but not the slope at which it is measured, influence the changes in Cr with fatigue. The mechanism by which Cr increases only in SHORT is not related to increased cost of breathing.

Redox regulation of E3 ubiquitin ligases and their role in skeletal muscle atrophy.

Muscle atrophy is linked to reactive oxygen species (ROS) production during hindlimb-unloading due, at least in part, to the activation of xanthine oxidase (XO). The major aim of our study was to determine the mechanism by which ROS cause muscle atrophy and its possible prevention by allopurinol, a well-known inhibitor of XO widely used in clinical practice, and indomethacin, a nonsteroidal anti-inflammatory drug. We studied the activation of p38 MAP Kinase and NF-?B pathways, and the expression of two E3 ubiquitin ligases involved in proteolysis, the Muscle atrophy F-Box (MAFb) and Muscle RING Finger-1 (MuRF-1). Male Wistar rats (3 mold) conditioned by 14 days of hindlimb unloading (n=18), with or without the treatment, were compared with freely ambulating controls (n=18). After the experimental intervention, soleus muscles were removed, weighted and analyzed to determine oxidative stress and inflammatory parameters. We found that hindlimb unloading induced a significant increase in XO activity in plasma (39%, p=0.001) and in the protein expression of CuZnSOD and Catalase in skeletal muscle. Inhibitionof XO partially prevented protein carbonylation, both in plasma and in soleus muscle, in the unloaded animals. The most relevant new fact reported is that allopurinol prevents soleus muscle atrophy by ~20% after hindlimb unloading. Combining allopurinol and indomethacin we found a further prevention in the atrophy process. This is mediated by the inhibition of the p38 MAPK-MAFbx and NF-?B -MuRF-1 pathways. Our data point out the potential benefit of allopurinol and indomethacin administration for bedridden, astronauts, sarcopenic and cachexic patients.

Humeral surface replacement for osteoarthritis.

BACKGROUND AND PURPOSE: Humeral resurfacing has shown promising results for osteoarthritis, but revisions for glenoid erosion have been reported frequently. We investigated the hypothesis that preoperative glenoid wear and postoperative progress of glenoid erosion would influence the clinical outcome. METHODS: We reviewed 61 resurfacing hemiarthroplasties (55 patients) for primary osteoarthritis. 6 patients were lost to follow-up and 5 had undergone revision arthroplasty. This left 50 shoulders in 44 patients (mean age 66 years) that were followed for mean 30 (12-44) months. Complications, revisions, and the age- and sex-related Constant score were assessed. Radiographs were evaluated for loosening and glenoid erosion according to Walch. RESULTS: Of the 50 shoulders that were functionally assessed, the average age- and sex-related Constant score was 73%. In patients with preoperative type-B2 glenoids, at 49% it was lower than in type-A1 glenoids (81%, p = 0.03) and in type-B1 glenoids (84%, p = 0.02). The average age- and sex-related Constant score for patients with type-A2 glenoids (60%) was lower than for type-A1 and -B1 glenoids and higher than for type-B2 glenoids, but the differences were not statistically significant. In the total population of 61 shoulders, the radiographs showed postoperative glenoid erosion in 38 cases and no humeral prosthetic loosening. Revision arthroplasty was performed in 11 cases after 28 (7-69) months. The implant size had no statistically significant influence on the functional outcome. The size was considered to be adequate in 28 of the 50 functionally assessed shoulders. In 21 cases, the implant size was too large and in 1 case it was too small. INTERPRETATION: We found frequent postoperative glenoid erosion and a high rate of revision arthroplasty after humeral resurfacing for primary osteoarthritis. Oversizing of the implants was common, but it had no statistically significant influence on the functional outcome. Inferior results were found in the presence of increased eccentric preoperative glenoid wear. Total shoulder arthroplasty should be considered in these patients.

Bone mineralization defects and vitamin D deficiency: histomorphometric analysis of iliac crest bone biopsies and circulating 25-hydroxyvitamin D in 675 patients.

Parathyroid hormone (PTH) is only one measurable index of skeletal health, and we reasoned that a histomorphometric analysis of iliac crest biopsies would be another and even more direct approach to assess bone health and address the required minimum 25-Hydroxyvitamin D [25(OH)D] level. A cohort from the northern European population with its known high prevalence of vitamin D deficiency therefore would be ideal to answer the latter question. We examined 675 iliac crest biopsies from male and female individuals, excluding all patients who showed any signs of secondary bone diseases at autopsy. Structural histomorphometric parameters, including osteoid indices, were quantified using the Osteomeasure System according to ASBMR standards, and serum 25(OH)D levels were measured for all patients. Statistical analysis was performed by Student's t test. The histologic results demonstrate an unexpected high prevalence of mineralization defects, that is, a pathologic increase in osteoid. Indeed, 36.15% of the analyzed patients presented with an osteoid surface per bone surface (OS/BS) of more than 20%. Based on the most conservative threshold that defines osteomalacia at the histomorphometric level with a pathologic increase in osteoid volume per bone volume (OV/BV) greater than 2% manifest mineralization defects were present in 25.63% of the patients. The latter were found independent of bone volume per trabecular volume (BV/TV) throughout all ages and affected both sexes equally. While we could not establish a minimum 25(OH)D level that was inevitably associated with mineralization defects, we did not find pathologic accumulation of osteoid in any patient with circulating 25(OH)D above 75 nmol/L. Our data demonstrate that pathologic mineralization defects of bone occur in patients with a serum 25(OH)D below 75 nmol/L and strongly argue that in conjunction with a sufficient calcium intake, the dose of vitamin D supplementation should ensure that circulating levels of 25(OH)D reach this minimum threshold (75 nmol/L or 30 ng/mL) to maintain skeletal health.