Peak Oxygen Uptake is Slope Dependent: Insights from Ground Reaction Forces and Muscle Oxygenation in Trained Male Runners.

BACKGROUND: The aim of this study is to explore the effect of treadmill slope on ground reaction forces and local muscle oxygenation as putative limiting factors of peak oxygen uptake in graded maximal incremental running tests. Thirteen trained male runners completed five maximal incremental running tests on treadmill at - 15%, - 7.5%, 0%, 7.5% and 15% slopes while cardiorespiratory and local muscle oxygenation responses as well as ground reaction forces were continuously recorded. Blood lactate concentration and isometric knee extensor torque were measured before and after each test. RESULTS: Peak oxygen uptake was lower at - 15% slope compared to all other conditions (from - 10 to - 17% lower, p < 0.001), with no difference between - 7.5 and + 15% slope. Maximal heart rate and ventilation values were reached in all conditions. The negative external mechanical work increased from steep uphill to steep downhill slopes (from 6 to 92% of total external work) but was not correlated with the peak oxygen uptake reduction. Local muscle oxygenation remained higher in - 15% slope compared to level running (p = 0.003). CONCLUSIONS: Similar peak oxygen uptake can be reached in downhill running up to - 7.5% slope. At more severe downhill slopes (i.e., - 15%), greater negative muscle work and limited local muscle deoxygenation occurred, even in subjects familiarized to downhill running, presumably preventing the achievement of similar to other condition's peak oxygen uptake. KEY POINTS: Trained male runners can reach like level running V̇O2peak at moderate but not at severe negative slope. Negative external mechanical work increases with increasing negative slope. At maximal intensity Vastus Lateralis muscle oxygenation is higher in steep negative slope. Knee extensor isometric muscle torque is preserved after maximal level and uphill running, but reduced after downhill running, despite lower blood lactate. Progressive reduction of V̇O2 at maximal effort with increasing negative slope might be related to the metabolic consequences of increased lower limb negative external work (i.e., eccentric muscle actions).

Impact of Eccentric versus Concentric Cycling Exercise on Neuromuscular Fatigue and Muscle Damage in Breast Cancer Patients.

INTRODUCTION: This study investigated the magnitude and etiology of neuromuscular fatigue and muscle damage induced by eccentric cycling compared to conventional concentric cycling in patients with breast cancer. METHODS: After a gradual familiarization protocol for eccentric cycling, nine patients with early-stage breast cancer performed three cycling sessions in eccentric or concentric mode. The eccentric cycling session (ECC) was compared to concentric cycling sessions matched for power output (CONpower, 80% of concentric peak power output, 95 ± 23 W) or oxygen uptake (10 ± 2 mL.min.kg-1). Pre- to postexercise changes (30s through 10 min recovery) in knee extensor maximal voluntary contraction force (MVC), voluntary activation, and quadriceps potentiated twitch force (Qtw) were quantified to determine global, central, and peripheral fatigue, respectively. Creatine kinase (CK) and lactate dehydrogenase (LDH) activities were measured in the plasma before and 24 h postexercise as markers of muscle damage. RESULTS: Compared to CONpower (-11 ± 9%) and (-5 ± 5%), the ECC session resulted in a greater decrease in MVC (-25 ± 12%) postexercise (P < 0.001). Voluntary activation decreased only in ECC (-9 ± 6% postexercise, P < 0.001). The decrease in Qtw was similar postexercise between ECC and CONpower (-39 ± 21% and -40 ± 16%, P > 0.99) but lower in (P < 0.001). The CONpower session resulted in twofold greater compared to the ECC and sessions (P < 0.001). No change in CK or LDH activity was reported from preexercise to 24 h postexercise. CONCLUSIONS: The ECC session induced greater neuromuscular fatigue compared to the concentric cycling sessions without generating severe muscle damage. ECC is a promising exercise modality for counteracting neuromuscular maladaptation in patients with breast cancer.

Energy Cost of Running in Well-Trained Athletes: Toward Slope-Dependent Factors.

PURPOSE: This study aimed to determine the contribution of metabolic, cardiopulmonary, neuromuscular, and biomechanical factors to the energy cost (ECR) of graded running in well-trained runners. METHODS: Eight men who were well-trained trail runners (age: 29 [10] y, mean [SD]; maximum oxygen consumption: 68.0 [6.4] mL·min-1·kg-1) completed maximal isometric evaluations of lower limb extensor muscles and 3 randomized trials on a treadmill to determine their metabolic and cardiovascular responses and running gait kinematics during downhill (DR: -15% slope), level (0%), and uphill running (UR: 15%) performed at similar O2 uptake (approximately 60% maximum oxygen consumption). RESULTS: Despite similar O2 demand, ECR was lower in DR versus level running versus UR (2.5 [0.2] vs 3.6 [0.2] vs 7.9 [0.5] J·kg-1·m-1, respectively; all P < .001). Energy cost of running was correlated between DR and level running conditions only (r2 = .63; P = .018). Importantly, while ECR was correlated with heart rate, cardiac output, and arteriovenous O2 difference in UR (all r2 > .50; P < .05), ECR was correlated with lower limb vertical stiffness, ground contact time, stride length, and step frequency in DR (all r2 > .58; P < .05). Lower limb isometric extension torques were not related to ECR whatever the slope. CONCLUSION: The determining physiological factors of ECR might be slope specific, mainly metabolic and cardiovascular in UR versus mainly neuromuscular and mechanical in DR. This possible slope specificity of ECR during incline running opens the way for the implementation of differentiated physiological evaluations and training strategies to optimize performance in well-trained trail runners.

Performance Profile among Age Categories in Young Cyclists.

Endurance profile assessment is of major interest to evaluate the cyclist's performance potential. In this regard, maximal oxygen uptake and functional threshold power are useful functional parameters to determine metabolic training zones (ventilatory threshold). The aim of this study was to evaluate and compare the physiological profile of different road cyclist age categories (Youth, Junior, and Under-23) to obtain the performance requirements. Sixty-one competitive road cyclists (15-22 years) performed a maximal incremental test on a bike in order to determine functional parameters (maximal fat oxidation zone, ventilatory thresholds, maximal oxygen uptake, and functional threshold power) and metabolic training zones. The results suggest major differences, with the Youth group showing clear changes in all metabolic zones except in fat oxidation. The main differences between Under-23 vs. Junior groups were observed in maximal relative power output (Under-23: 6.70 W·Kg-1; Junior: 6.17 W·Kg-1) and relative functional threshold power (Under-23: 4.91 W·Kg-1; Junior: 4.48 W·Kg-1). The Youth group physiological profile is clearly different to the other age categories. Some parameters normalized to body weight (maximal oxygen consumption, load and functional threshold power) could be interesting to predict a sporting career during the Junior and Under-23 stages.

Professional cyclists have lower levels of bone markers than amateurs. Is there a risk of osteoporosis in cyclist?

Currently, there is a greater number of amateurs that practice cycling. However, there is no clear evidence regarding bone health in amateur cyclists compared to professional cyclists, as the latter has shown to have lower bone mineral content and density. Therefore, the aim of this study was to identify the differences in bone variables between professional (PRO) and amateur (AMA) road cyclists, and to see if these differences were related to differences in cycling performance. A parallel trial was carried out with 15 AMA and 10 PRO cyclists. All cyclists visited the laboratory twice: 1) in a fasted state, body composition measured by dual-energy X-ray absorptiometry (DXA) and 2) physiological variables measured using an incremental test until exhaustion. Significantly lower values were found in bone mineral density, bone mineral content and fat free mass in PRO compared to AMA (p < 0.05). In addition, significantly higher power was produced in ventilatory thresholds 1 and 2 (VT1 and VT2) and VO2MAX in PRO compared to AMA (p < 0.05). Overall, PRO cyclists had lower values in bone health and muscle mass but better results in performance compared to AMA.

The Impact of Coronavirus (COVID-19) Related Public-Health Measures on Training Behaviours of Individuals Previously Participating in Resistance Training: A Cross-Sectional Survey Study.

INTRODUCTION: Understanding the impact of lockdown upon resistance training (RT), and how people adapted their RT behaviours, has implications for strategies to maintain engagement in similar positive health behaviours. Further, doing so will provide a baseline for investigation of the long-term effects of these public health measures upon behaviours and perceptions, and facilitate future follow-up study. OBJECTIVES: To determine how the onset of coronavirus (COVID-19), and associated 'lockdown', affected RT behaviours, in addition to motivation, perceived effectiveness, enjoyment, and intent to continue, in those who regularly performed RT prior to the pandemic. METHODS: We conducted an observational, cross-sectional study using online surveys in multiple languages (English, Danish, French, German, Italian, Portuguese, Slovakian, Swedish, and Japanese) distributed across social media platforms and through authors' professional and personal networks. Adults (n = 5389; median age = 31 years [interquartile range (IQR) = 25, 38]), previously engaged in RT prior to lockdown (median prior RT experience = 7 years [IQR = 4, 12]) participated. Outcomes were self-reported RT behaviours including: continuation of RT during lockdown, location of RT, purchase of specific equipment for RT, method of training, full-body or split routine, types of training, repetition ranges, exercise number, set volumes (per exercise and muscle group), weekly frequency of training, perception of effort, whether training was planned/recorded, time of day, and training goals. Secondary outcomes included motivation, perceived effectiveness, enjoyment, and intent to continue RT. RESULTS: A majority of individuals (82.8%) maintained participation in RT during-lockdown. Marginal probabilities from generalised linear models and generalised estimating equations for RT behaviours were largely similar from pre- to during-lockdown. There was reduced probability of training in privately owned gyms (~ 59% to ~ 7%) and increased probability of training at home (~ 18% to ~ 89%); greater probability of training using a full-body routine (~ 38% to ~ 51%); reduced probability of resistance machines (~ 66% to ~ 13%) and free weight use (~ 96% to ~ 81%), and increased probability of bodyweight training (~ 62% to ~ 82%); reduced probability of moderate repetition ranges (~ 62-82% to ~ 55-66%) and greater probability of higher repetition ranges (~ 27% to ~ 49%); and moderate reduction in the perception of effort experienced during-training (r = 0.31). Further, individuals were slightly less likely to plan or record training during lockdown and many changed their training goals. Additionally, perceived effectiveness, enjoyment, and likelihood of continuing current training were all lower during-lockdown. CONCLUSIONS: Those engaged in RT prior to lockdown these behaviours with only slight adaptations in both location and types of training performed. However, people employed less effort, had lower motivation, and perceived training as less effective and enjoyable, reporting their likelihood of continuing current training was similar or lower than pre-lockdown. These results have implications for strategies to maintain engagement in positive health behaviours such as RT during-restrictive pandemic-related public health measures. PRE-REGISTRATION: https://osf.io/qcmpf . PREPRINT: The preprint version of this work is available on SportRχiv: https://osf.io/preprints/sportrxiv/b8s7e/ .

Differences between Professional and Amateur Cyclists in Endogenous Antioxidant System Profile.

Currently, no studies have examined the differences in endogenous antioxidant enzymes in professional and amateur cyclists and how these can influence sports performance. The aim of this study was to identify differences in endogenous antioxidants enzymes and hemogram between competitive levels of cycling and to see if differences found in these parameters could explain differences in performance. A comparative trial was carried out with 11 professional (PRO) and 15 amateur (AMA) cyclists. All cyclists performed an endogenous antioxidants analysis in the fasted state (visit 1) and an incremental test until exhaustion (visit 2). Higher values in catalase (CAT), oxidized glutathione (GSSG) and GSSG/GSH ratio and lower values in superoxide dismutase (SOD) were found in PRO compared to AMA (p < 0.05). Furthermore, an inverse correlation was found between power produced at ventilation thresholds 1 and 2 and GSSG/GSH (r = -0.657 and r = -0.635; p < 0.05, respectively) in PRO. Therefore, there is no well-defined endogenous antioxidant enzyme profile between the two competitive levels of cyclists. However, there was a relationship between GSSG/GSH ratio levels and moderate and submaximal exercise performance in the PRO cohort.

Physiological factors determining downhill vs uphill running endurance performance.

OBJECTIVES: Recent studies investigated the determinants of trail running performance (i.e., combining uphill (UR) and downhill running sections (DR)), while the possible specific physiological factors specifically determining UR vs DR performances (i.e., isolating UR and DR) remain presently unknown. This study aims to determine the cardiorespiratory responses to outdoor DR vs UR time-trial and explore the determinants of DR and UR performance in highly trained runners. DESIGN: Randomized controlled trial. METHODS: Ten male highly-trained endurance athletes completed 5-km DR and UR time-trials (average grade: ±8%) and were tested for maximal oxygen uptake, lower limb extensor maximal strength, local muscle endurance, leg musculotendinous stiffness, vertical jump ability, explosivity/agility and sprint velocity. Predictors of DR and UR performance were investigated using correlation and commonality regression analyses. RESULTS: Running velocity was higher in DR vs UR time-trial (20.4±1.0 vs 12.0±0.5km·h-1, p<0.05) with similar average heart rate (95±2% vs 94±2% maximal heart rate; p>0.05) despite lower average V̇O2 (85±8% vs 89±7% V̇O2max; p<0.05). Velocity at V̇O2max (vV̇O2max) body mass index (BMI) and maximal extensor strength were significant predictors of UR performance (r2=0.94) whereas vV̇O2max, leg musculotendinous stiffness and maximal extensor strength were significant predictors of DR performance (r2=0.84). CONCLUSIONS: Five-km UR and DR running performances are both well explained by three independent predictors. If two predictors are shared between UR and DR performances (vV̇O2max and maximal strength), their relative contribution is different and, importantly, the third predictor appears very specific to the exercise modality (BMI for UR vs leg musculotendinous stiffness for DR).

High-intensity downhill running exacerbates heart rate and muscular fatigue in trail runners.

This study explores the cardiorespiratory and muscular fatigue responses to downhill (DR) vs uphill running (UR) at similar running speed or similar oxygen uptake (⩒O2). Eight well-trained, male, trail runners completed a maximal level incremental test and three 15-min treadmill running trials at ±15% slope: i) DR at ~6 km·h-1 and ~19% ⩒O2max (LDR); ii) UR at ~6 km·h-1 and ~70% ⩒O2max (HUR); iii) DR at ~19 km·h-1 and ~70% ⩒O2max (HDR). Cardiorespiratory responses and spatiotemporal gait parameters were measured continuously. Maximal isometric torque was assessed before and after each trial for hip and knee extensors and plantar flexor muscles. At similar speed (~6 km·h-1), cardiorespiratory responses were attenuated in LDR vs HUR with altered running kinematics (all p < 0.05). At similar ⩒O2 (~3 l·min-1), heart rate, pulmonary ventilation and breathing frequency were exacerbated in HDR vs HUR (p < 0.01), with reduced torque in knee (-15%) and hip (-11%) extensors and altered spatiotemporal gait parameters (all p < 0.01). Despite submaximal metabolic intensity (70% ⩒O2max), heart rate and respiratory frequency reached maximal values in HDR. These results further our understanding of the particular cardiorespiratory and muscular fatigue responses to DR and provide the bases for future DR training programs for trail runners.

Small-Sided Games Are Not as Effective as Intermittent Running to Stimulate Aerobic Metabolism in Prepubertal Soccer Players.

PURPOSE: The purpose of this study was to investigate the influence of the soccer pitch area during small-sided games (SSG) in prepubertal children on physiological and technical demands, and to compare them, for the physiological demands, to high-intensity interval training (HIIT). METHODS: Ten young soccer players (13.0 [0.3] y) performed a HIIT and 3 SSG of various field sizes (30 × 20 m, 42 × 38 m, and 51 × 34 m). Each SSG was performed with 5 players per team, during 4 × 4-minutes interspaced with 1 minute of passive recovery in between. HIIT also followed a 4 × 4-minute protocol with running speed set on an individual basis. Heart rate (HR) was continuously monitored during training sessions. For each exercise modality, time spent above 90% of HRmax (T≥90%,HRmax) was calculated, and technical actions were quantified during SSG by video analysis. RESULTS: T≥90%,HRmax was similar between the 3 SSG (∼587 [276] s; P > .2) but 24% to 37% lower than during HIIT (826 [140] s, P < .05). Coefficients of variations in T≥90%,HRmax were 2.3 to 3.5 times larger in SSG compared with HIIT. For technical actions, greater number of possessions (21 [6] vs ∼14 [4]), and lower ball touches per possession (2.4 [0.6] vs ∼2.9 [0.6]) were found in the small SSG compared with larger SSG, respectively (P < .05). CONCLUSION: The 3 SSG led to lower acute stimulation of the aerobic metabolism, suggesting a lower potential for chronic aerobic adaptations, compared with HIIT. Moreover, interindividual variability in the physiological response was substantially greater in SSG compared with HIIT, indicating increased heterogeneity among players performing the same training protocol.

Evolution of Physical Status From Diagnosis to the End of First-Line Treatment in Breast, Lung, and Colorectal Cancer Patients: The PROTECT-01 Cohort Study Protocol.

Background: Cancer cachexia and exacerbated fatigue represent two hallmarks in cancer patients, negatively impacting their exercise tolerance and ultimately their quality of life. However, the characterization of patients' physical status and exercise tolerance and, most importantly, their evolution throughout cancer treatment may represent the first step in efficiently counteracting their development with prescribed and tailored exercise training. In this context, the aim of the PROTECT-01 study will be to investigate the evolution of physical status, from diagnosis to the end of first-line treatment, of patients with one of the three most common cancers (i.e., lung, breast, and colorectal). Methods: The PROTECT-01 cohort study will include 300 patients equally divided between lung, breast and colorectal cancer. Patients will perform a series of assessments at three visits throughout the treatment: (1) between the date of diagnosis and the start of treatment, (2) 8 weeks after the start of treatment, and (3) after the completion of first-line treatment or at the 6-months mark, whichever occurs first. For each of the three visits, subjective and objective fatigue, maximal voluntary force, body composition, cachexia, physical activity level, quality of life, respiratory function, overall physical performance, and exercise tolerance will be assessed. Discussion: The present study is aimed at identifying the nature and severity of maladaptation related to exercise intolerance in the three most common cancers. Therefore, our results should contribute to the delineation of the needs of each group of patients and to the determination of the most valuable exercise interventions in order to counteract these maladaptations. This descriptive and comprehensive approach is a prerequisite in order to elaborate, through future interventional research projects, tailored exercise strategies to counteract specific symptoms that are potentially cancer type-dependent and, in fine, to improve the health and quality of life of cancer patients. Moreover, our concomitant focus on fatigue and cachexia will provide insightful information about two factors that may have substantial interaction but require further investigation. Trial registration: This prospective study has been registered at ClinicalTrials.gov (NCT03956641), May, 2019.

Trail Runners Cannot Reach V˙O2max during a Maximal Incremental Downhill Test.

PURPOSE: The purpose of this study was twofold: (i) determine if well-trained athletes can achieve similar peak oxygen uptake (V˙O2peak) in downhill running (DR) versus level running (LR) or uphill running (UR) and (ii) investigate if lower limb extensor muscle strength is related to the velocity at V˙O2peak (vV˙O2peak) in DR, LR, and UR. METHODS: Eight athletes (V˙O2max = 68 ± 2 mL·min·kg) completed maximal incremental tests in LR, DR (-15% slope), and UR (+15% slope) on a treadmill (+1, +1.5, and +0.5 km·h every 2 min, respectively) while cardiorespiratory responses and spatiotemporal running parameters were continuously measured. They were also tested for maximal voluntary isometric strength of hip and knee extensors and plantar flexors. RESULTS: Oxygen uptake at maximal effort was approximately 16% to 18% lower in DR versus LR and UR (~57 ± 2 mL·min·kg, 68 ± 2 mL·min·kg, and 70 ± 3 mL·min·kg, respectively) despite much greater vV˙O2peak (22.7 ± 0.6 km·h vs 18.7 ± 0.5 km·h and 9.3 ± 0.3 km·h, respectively). At vV˙O2peak, longer stride length and shorter contact time occurred in DR versus LR and UR (+12%, +119%, -38%, and -61%, respectively). Contrary to knee extensor and plantar flexor, hip extensor isometric strength correlated to vV˙O2peak in DR, LR, and UR (r = -0.86 to -0.96, P < 0.05). At similar V˙O2, higher heart rate and ventilation emerged in DR versus LR and UR, associated with a more superficial ventilation pattern. CONCLUSIONS: This study demonstrates that well-trained endurance athletes, accustomed to DR, achieved lower V˙O2peak despite higher vV˙O2peak during DR versus LR or UR maximal incremental tests. The specific heart rate and ventilation responses in DR might originate from altered running gait and increased lower-limb musculotendinous mechanical loading, furthering our understanding of the particular physiology of DR, ultimately contributing to optimize trail race running performance.

Cardiorespiratory Responses to Downhill Versus Uphill Running in Endurance Athletes.

PURPOSE: Mountain running races are becoming increasingly popular, although our understanding of the particular physiology associated with downhill running (DR) in trained athletes remains scarce. This study explored the cardiorespiratory responses to high-slope constant velocity uphill running (UR) and DR. METHOD: Eight endurance athletes performed a maximal incremental test and 2 15-min running bouts (UR, +15%, or DR, -15%) at the same running velocity (8.5 ± 0.4 km·h-1). Oxygen uptake ([Formula: see text]O2), heart rate (HR), and ventilation rates ([Formula: see text]E) were continuously recorded, and blood lactate (bLa) was measured before and after each trial. RESULTS: Downhill running induced a more superficial [Formula: see text]E pattern featuring reduced tidal volume (p < .05, ES = 6.05) but similar respiratory frequency (p > .05, ES = 0.68) despite lower [Formula: see text]E (p < .05, ES = 5.46), [Formula: see text]O2 (p < .05, ES = 12.68), HR (p < .05, ES = 6.42), and bLa (p < .05, ES = 1.70). A negative slow component was observed during DR for [Formula: see text]O2 (p < .05, ES = 1.72) and HR (p < .05, ES = 0.80). CONCLUSIONS: These results emphasize the cardiorespiratory responses to DR and highlight the need for cautious interpretation of [Formula: see text]O2, HR, and [Formula: see text]E patterns as markers of exercise intensity for training load prescription and management.

Moderate Exercise Allows for shorter Recovery Time in Critical Limb Ischemia.

Whether and how moderate exercise might allow for accelerated limb recovery in chronic critical limb ischemia (CLI) remains to be determined. Chronic CLI was surgically induced in mice, and the effect of moderate exercise (training five times per week over a 3-week period) was investigated. Tissue damages and functional scores were assessed on the 4th, 6th, 10th, 20th, and 30th day after surgery. Mice were sacrificed 48 h after the last exercise session in order to assess muscle structure, mitochondrial respiration, calcium retention capacity, oxidative stress and transcript levels of genes encoding proteins controlling mitochondrial functions (PGC1α, PGC1ß, NRF1) and anti-oxidant defenses markers (SOD1, SOD2, catalase). CLI resulted in tissue damages and impaired functional scores. Mitochondrial respiration and calcium retention capacity were decreased in the ischemic limb of the non-exercised group (Vmax = 7.11 ± 1.14 vs. 9.86 ± 0.86 mmol 02/min/g dw, p < 0.001; CRC = 7.01 ± 0.97 vs. 11.96 ± 0.92 microM/mg dw, p < 0.001, respectively). Moderate exercise reduced tissue damages, improved functional scores, and restored mitochondrial respiration and calcium retention capacity in the ischemic limb (Vmax = 9.75 ± 1.00 vs. 9.82 ± 0.68 mmol 02/min/g dw; CRC = 11.36 ± 1.33 vs. 12.01 ± 1.24 microM/mg dw, respectively). Exercise also enhanced the transcript levels of PGC1α, PGC1ß, NRF1, as well as SOD1, SOD2, and catalase. Moderate exercise restores mitochondrial respiration and calcium retention capacity, and it has beneficial functional effects in chronic CLI, likely by stimulating reactive oxygen species-induced biogenesis and anti-oxidant defenses. These data support further development of exercise therapy even in advanced peripheral arterial disease.

Biochemical responses and physical performance during high-intensity resistance circuit training in hypoxia and normoxia.

PURPOSE: The aim of this study was to analyze the effect of hypoxia on metabolic and acid-base balance, blood oxygenation, electrolyte, and half-squat performance variables during high-resistance circuit (HRC) training. METHODS: Twelve resistance-trained subjects participated in this study. After a 6RM testing session, participants performed three randomized trials of HRC: normoxia (NORM: FiO2 = 0.21), moderate hypoxia (MH: FiO2 = 0.16), or high hypoxia (HH: FiO2 = 0.13), separated by 72 h of recovery in normoxic conditions. HRC consisted of two blocks of three exercises (Block 1: bench press, deadlift and elbow flexion; Block 2: half-squat, triceps extension, and ankle extension). Each exercise was performed at 6RM. Rest periods lasted for 35 s between exercises, 3 min between sets, and 5 min between blocks. Peak and mean force and power were determined during half-squat. Metabolic, acid-base balance, blood oxygenation and electrolyte variables, arterial oxygen saturation (SaO2), and rating of perceived exertion (RPE) were measured following each block. RESULTS: During the first set, peak force and power were significantly lower in HH than MH and NORM; whereas in the second set, mean and peak force and power were significantly lower in HH than NORM. At the end of the HRC training session, blood lactate and RPE in HH were significantly higher than in MH and NORM. SaO2, pH, HCO3-, and pO2 values were significantly lower in all hypoxic conditions than in NORM. CONCLUSION: These results indicate that simulated hypoxia during HRC exercise reduce blood oxygenation, pH, and HCO3-, and increased blood lactate ultimately decreasing muscular performance.

Cardio-respiratory responses to hypoxia combined with CO2 inhalation during maximal exercise.

We measured the effects of adding CO2 to an inhaled hypoxic gas mixture on cardio-respiratory parameters during maximal exercise. Eight young males performed four incremental maximal exercise tests on cycle under ambient air, hypoxia (FIO2 0.125), inhaled CO2 (FICO2 0.045), and combination of hypoxia and inhaled CO2. The highest ventilation (VE) and VE/CO2 output were recorded in CO2 inhalation and combined treatments. Arterial O2 partial pressure was higher in combined than in hypoxia treatment, but the difference between the treatments narrowed from rest to end-exercise, at least partly because the magnitude of the increase in VE (%) at exercise was smaller in combined treatment than in hypoxia. Arterial O2 content was higher in combined treatment than in hypoxia at rest, but no more at maximal exercise. Cardiac output was higher and O2 extraction lower when breathing O2-poor gas mixtures than under the two other treatments. For a given oxygen consumption, hypoxia and combined treatment showed similar cardiac output and O2 extraction.

Comparative assessment of knee extensor and flexor muscle strength measured using a hand-held vs. isokinetic dynamometer.

[Purpose] To compare measurements of knee extensor and flexor muscle strength performed using a hand-held dynamometer and an isokinetic dynamometer in apparently healthy subjects. [Subjects and Methods] Thirty adult volunteers underwent knee muscle strength evaluation using an isokinetic or a hand-held dynamometer. [Results] Strong positive correlations were found between the 2 methods, with correlation coefficients r ranging from 0.72 (95% confidence interval [CI], 0.48-0.86) to 0.87 (95% CI, 0.75-0.94), depending on the muscle group and the isokinetic evaluation mode. The reproducibility of the hand-held dynamometer findings was good, judged by a coefficient of variation of 3.2-4.2%. However, the correlation between the 2 methods for the assessment of flexor/extensor ratios ranged from -0.04 to 0.46. [Conclusion] Knee extensor and flexor muscle strength recorded with a hand-held dynamometer is reproducible and significantly correlated with the isokinetic values, indicating that this method may in some cases be a useful replacement for isokinetic strength measurement. However, for strength ratio assessment, and when judged against the isokinetic standard, a hand-held dynamometer is not a valid option.

High-Force Versus Low-Force Lumbar Traction in Acute Lumbar Sciatica Due to Disc Herniation: A Preliminary Randomized Trial.

OBJECTIVE: This study compared the effects of high-force versus low-force lumbar traction in the treatment of acute lumbar sciatica secondary to disc herniation. METHODS: A randomized double blind trial was performed, and 17 subjects with acute lumbar sciatica secondary to disc herniation were assigned to high-force traction at 50% body weight (BW; LT50, n = 8) or low force traction at 10% BW (LT10, n = 9) for 10 sessions in 2 weeks. Radicular pain (visual analogue scale [VAS]), lumbo-pelvic-hip complex motion (finger-to-toe test), lumbar-spine mobility (Schöber-Macrae test), nerve root compression (straight-leg-raising test), disability (EIFEL score), drug consumption, and overall evaluation of each patient were measured at days 0, 7, 1, 4, and 28. RESULTS: Significant (P < .05) improvements were observed in the LT50 and LT10 groups, respectively, between day 0 and day 14 (end of treatment) for VAS (-44% and -36%), EIFEL score (-43% and -28%) and overall patient evaluation (+3.1 and +2.0 points). At that time, LT50 specifically improved in the finger-to-toe test (-42%), the straight-leg-raising test (+58), and drug consumption (-50%). No significant interaction effect (group-by-time) was revealed, and the effect of traction treatment was independent of the level of medication. During the 2-week follow-up at day 28, only the LT10 group improved (P < .05) in VAS (-52%) and EIFEL scores (-46%). During this period, no interaction effect (group-by-time) was identified, and the observed responses were independent of the level of medication. CONCLUSIONS: For this preliminary study, patients with acute lumbar sciatica secondary to disc herniation who received 2 weeks of lumbar traction reported reduced radicular pain and functional impairment and improved well-being regardless of the traction force group to which they were assigned. The effects of the traction treatment were independent of the initial level of medication and appeared to be maintained at the 2-week follow-up.