The load borne by the Achilles tendon during exercise: A systematic review of normative values.

The Achilles tendon (AT) can be exposed to considerable stress during athletic activities and is often subject to pathologies such as tendinopathies. When designing a prevention or rehabilitation protocol, mechanical loading is a key factor to consider. This implies being able to accurately determine the load applied to the AT when performing exercises that stress this tendon. A systematic review was performed to synthesize the load borne by the AT during exercises/activities. Three databases (Pubmed, Embase and Cochrane) were searched for articles up to May 2021, and only the studies assessing the AT load in newtons relative to body-weight (BW) on humans during activities or exercises were included. Most of the 11 included studies assessed AT load when running or walking (N = 10), and only three tested exercises were usually performed during rehabilitation. The load on the tendon ranged from 2.7 to 3.95 BW when walking, from 4.15 to 7.71 BW when running, and from 0.41 to 7.3 BW according to the strengthening exercise performed. From the collected data, a progression of exercises progressively loading the Achilles tendon, as well as the possible connections with walking and running activities, could be defined. However, the trends highlighted in the relationship between tendon loading and walking or running speeds present some inconsistencies. Further research is still needed to clarify them, but also to complete the data set in healthy and injured people.

Sleep-disordered breathing and daytime postural stability.

OBJECTIVE: Postural stability depends on the coordination of the central nervous system with visual sense, proprioceptive and vestibular information. Sleep deprivation has been shown to affect this function. The objective of our study was to assess the effects of sleep-disordered breathing (SDB) on postural stability. METHODS: 158 subjects referred for suspected SDB had an overnight sleep study and were placed on a posturographic platform in late afternoon. This platform allows measuring the centre of pressure (CoP) oscillations and to calculate: total displacement of CoP in X and Y axes, mean speed of CoP displacement and the length as function of surface (LFS) ratio (length of CoP displacement/surface of CoP trajectory). RESULTS: 98 men and 60 women were included. Mean age±SD was 45.4±5.5 years old, body mass index (BMI) 27.5±5.6 kg/m(2) and apnoea-hypopnoea index (AHI) 13.6±16.1/h. AHI was <5/h in 64 (41%) subjects, 5-15/h in 43 (27%), 15-30/h in 30 (19%) and >30/h in 21 (13%). In patients with an AHI >5/h versus AHI <5/h, we observed an important increase in LFS (+21%, p<0.001), in XY length (+23%, p<0.001) and in mean speed (+23%, p<0.001). After controlling for age, BMI and sleepiness (Epworth) in multivariate regression models, there was a positive association between all nocturnal breathing parameters (specifically: mean SpO2, AHI, oxygen desaturation index 3% and % time with SpO2 <90%) and the main stability outcomes (all p<0.05). CONCLUSIONS: SDB severity, especially the mean nocturnal SpO2 level, is associated with impaired daytime postural stability.

Comparison of Four Sections for Analyzing Running Mechanics Alterations During Repeated Treadmill Sprints.

We compared different approaches to analyze running mechanics alterations during repeated treadmill sprints. Thirteen active male athletes performed five 5-second sprints with 25 seconds of recovery on an instrumented treadmill. This approach allowed continuous measurement of running kinetics/kinematics and calculation of vertical and leg stiffness variables that were subsequently averaged over 3 distinct sections of the 5-second sprint (steps 2-5, 7-10, and 12-15) and for all steps (steps 2-15). Independently from the analyzed section, propulsive power and step frequency decreased with fatigue, while contact time and step length increased (P < .05). Except for step frequency, all mechanical variables varied (P < .05) across sprint sections. The only parameters that highly depend on running velocity (propulsive power and vertical stiffness) showed a significant interaction (P < .05) between the analyzed sections, with smaller magnitude of fatigue-induced change observed for steps 2-5. Considering all steps or only a few steps during early, middle, or late phases of 5-second sprints provides similar mechanical outcomes during repeated treadmill sprinting, although acceleration induces noticeable differences between the sections studied. Furthermore, quantifying mechanical alterations from the early acceleration phase may not be readily detectable, and is not recommended.

Sensorimotor control deficiency in recurrent anterior shoulder instability assessed with a stabilometric force platform.

BACKGROUND: Deficiencies in both afferent proprioceptive information and efferent motor responses have been independently reported in patients with recurrent anterior shoulder instability. We used a validated force platform method to analyze the association between the stabilometric parameters of the upper limb as representative of the shoulder's sensorimotor control and clinical glenohumeral joint instability. METHODS: We enrolled 32 patients with unilateral recurrent anterior post-traumatic shoulder dislocation, on the dominant side in 13 patients (DIG) and the non-dominant side in 19 patients (NDIG) and 16 healthy nonathletic subjects (CG). Displacements of the Center of Pressure were measured by a Win-Posturo Medicapteurs force platform in the upper limb weight-bearing position with the lower limbs resting on a table up to the anterior superior iliac spines. The association between stabilometric values and clinical shoulder instability was analyzed by side-to-side comparisons and comparisons to a control group. RESULTS: For CG and NDIG, there were no side-to-side differences. For DIG, stabilometric values were significantly higher on the dominant pathological shoulder side than on the healthy contralateral non-dominant side (P < .01). The percentage of side-to-side differences was higher in DIG than CG (P < .01). CONCLUSION: Sensorimotor control deficiency was associated with recurrent anterior shoulder instability, especially in patients with the pathological shoulder on their dominant side. Using a force platform to assess sensorimotor control of the shoulder is feasible in patients with shoulder instability, and can allow assessment of the global sensorimotor control deficiency present in unstable shoulders.

Supervised Exercise Training May Improve Postural Control in Patients with Symptomatic Lower Extremity Peripheral Artery Disease.

Patients with symptomatic peripheral artery disease (PAD) have been shown to present balance disorders and a history of falling, which are associated with functional and daily life impairments. Although postural control improvement is an important outcome, the benefits of supervised exercise training (SET) on postural control have been seldom investigated in these patients. This article investigates the effects of SET on traditional measures of postural control and on stabilogram-diffusion analysis (SDA) parameters in patients with symptomatic PAD. Patients with symptomatic chronic lower limb claudication were investigated. All subjects who completed the 3-month multimodal SET program and postural control assessment before and after SET were included. Center of pressure trajectory analysis and SDA parameters were investigated using a posturographic platform. Patients were instructed to stand on the platform and maintain balance to their best ability. Treadmill pain-free (PFWD) and maximal (MWD) walking distances were also assessed prior and following SET. Forty-four patients with PAD (65.2 ± 9.8 years, 34% women) were investigated. All postural control parameters were unchanged following SET, except the length of center of pressure displacement as a function of the surface of center of pressure trajectory (LFS), which was significantly increased (before SET: 1.4 ± 0.4; after SET: 1.5 ± 0.5; p = 0.042). PFWD (before SET: 103.5 ± 77.9 m; after SET: 176.8 ± 130.6 m; p ≤ 0.001) and MWD (before SET: 383.6 ± 272.0 m; after SET: 686.4 ± 509.0 m; p ≤ 0.001) significantly improved following SET. The increased LFS suggests a better postural control accuracy following SET in patients with symptomatic PAD.

Effect of hip flexion angle on hamstring optimum length after a single set of concentric contractions.

The eccentric contraction mode was proposed to be the primary stimulus for optimum angle (angle at which peak torque occurs) shift. However, the training range of motion (or muscle excursion range) could be a stimulus as important. The aim of this study was to assess the influence of the training range of motion stimulus on the hamstring optimum length. It was hypothesised that performing a single set of concentric contractions beyond optimal length (seated at 80° of hip flexion) would lead to an immediate shift of the optimum angle to longer muscle length while performing it below (supine at 0° of hip flexion) would not provide any shift. Eleven male participants were assessed on an isokinetic dynamometer. In both positions, the test consisted of 30 consecutive knee flexions at 4.19 rad · s⁻¹. The optimum angle was significantly shifted by ∼15° in the direction of longer muscle length after the contractions at 80° of hip flexion, while a non-significant shift of 3° was found at 0°. The hamstring fatigability was not influenced by the hip position. It was concluded that the training range of motion seems to be a relevant stimulus for shifting the optimum angle to longer muscle length. Moreover, fatigue appears as a mechanism partly responsible for the observed shift.

Changes in running mechanics and spring-mass behaviour induced by a 5-hour hilly running bout.

The aim of this study was to investigate changes in running mechanics and spring-mass behaviour with fatigue induced by 5-hour hilly running (5HHR). Running mechanics were measured pre- and post-5HHR at 10, 12 and 14 km · h(-1) on an instrumented treadmill in eight ultramarathon runners, and sampled at 1000 Hz for 10 consecutive steps. Contact (t(c) ) and aerial (t(a) ) times were determined from ground reaction force (GRF) signals and used to compute step frequency (f). Maximal GRF, loading rate, downward displacement of the centre of mass (Δz), and leg length change (ΔL) during the support phase were determined and used to compute both vertical (K(vert) ) and leg (K(leg) ) stiffness. A significant decrease in t(c) was observed at 12 and 14 km · h(-1) resulting in an increase of f at all speeds. Duty factor and F(max) significantly decreased at 10 km · h(-1). A significant increase in K(vert) and K(leg) was observed at all running speeds with significant decreases in Δz and ΔL. Despite the shorter duration, the changes in running mechanics appeared to be in the same direction (increased f and K(vert) , decrease in Δz and F(max) ) but of lower amplitude compared with those obtained after an ultra-trail or an ultramarathon.

Effects of a 5-h hilly running on ankle plantar and dorsal flexor force and fatigability.

This study aimed to examine the effects of a 5-h hilly run on ankle plantar (PF) and dorsal flexor (DF) force and fatigability. It was hypothesised that DF fatigue/fatigability would be greater than PF fatigue/fatigability. Eight male trail long distance runners (42.5 ± 5.9 years) were tested for ankle PF and DF maximal voluntary isokinetic contraction strength and fatigue resistance tests (percent decrement score), maximal voluntary and electrically evoked isometric contraction strength before and after the run. Maximal EMG root mean square (RMS(max)) and mean power frequency (MPF) values of the tibialis anterior (TA), gastrocnemius lateralis (GL) and soleus (SOL) EMG activity were calculated. The peak torque of the potentiated high- and low-frequency doublets and the ratio of paired stimulation peak torques at 10 Hz over 100 Hz (Db10:100) were analysed for PF. Maximal voluntary isometric contraction strength of PF decreased from pre- to post-run (-17.0 ± 6.2%; P < 0.05), but no significant decrease was evident for DF (-7.9 ± 6.2%). Maximal voluntary isokinetic contraction strength and fatigue resistance remained unchanged for both PF and DF. RMS(max) SOL during maximal voluntary isometric contraction and RMS(max) TA during maximal voluntary isokinetic contraction were decreased (P < 0.05) after the run. For MPF, a significant decrease for TA (P < 0.05) was found and the ratio Db10:100 decreased for PF (-6.5 ± 6.0%; P < 0.05). In conclusion, significant isometric strength loss was only detected for PF after a 5-h hilly run and was partly due to low-frequency fatigue. This study contradicted the hypothesis that neuromuscular alterations due to prolonged hilly running are predominant for DF.

Study of the Kinetics of the Determinants of Performance During a Mountain Ultramarathon: Multidisciplinary Protocol of the First Trail Scientifique de Clécy 2021.

BACKGROUND: The growing interest of the scientific community in trail running has highlighted the acute effects of practice at the time of these races on isolated aspects of physiological and structural systems; biological, physiological, cognitive, and muscular functions; and the psychological state of athletes. However, no integrative study has been conducted under these conditions with so many participants and monitoring of pre-, per-, and postrace variables for up to 10 days over a distance close to 100 miles. OBJECTIVE: The aim of this study was to evaluate the kinetics of the performance parameters during a 156 km trail run and 6000 m of elevation gain in pre-, per-, and postrace conditions. The general hypothesis is based on significant alterations in the psychological, physiological, mechanical, biological, and cognitive parameters. METHODS: The Trail Scientifique de Clécy took place on November 11, 2021. This prospective experimental study provides a comprehensive exploration of the constraints and adaptations of psychophysiological and sociological variables assessed in real race conditions during a trail running of 156 km on hilly ground and 6000 m of elevation gain (D+). The study protocol allowed for repeatability of study measurements under the same experimental conditions during the race, with the race being divided into 6 identical loops of 26 km and 1000 m D+. Measurements were conducted the day before and the morning of the race, at the end of each lap, after a pit stop, and up to 10 days after the race. A total of 55 participants were included, 43 (78%) men and 12 (22%) women, who were experienced in ultra-trail-running events and with no contraindications to the practice of this sport. RESULTS: The launch of the study was authorized on October 26, 2021, under the trial number 21-0166 after a favorable opinion from the Comité de Protection des Personnes Ouest III (21.09.61/SIRIPH 2G 21.01586.000009). Of the 55 runners enrolled, 41 (75%) completed the race and 14 (25%) dropped out for various reasons, including gastric problems, hypothermia, fatigue, and musculoskeletal injuries. All the measurements for each team were completed in full. The race times (ie, excluding the measurements) ranged from 17.8206 hours for the first runner to 35.9225 hours for the last runner. The average time to complete all measurements for each lap was 64 (SD 3) minutes. CONCLUSIONS: The Trail Scientifique de Clécy, by its protocol, allowed for a multidisciplinary approach to the discipline. This approach will allow for the explanation of the studied parameters in relation to each other and observation of the systems of dependence and independence. The initial results are expected in June 2022. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/38027.

From Sedentary and Physical Inactive Behaviours to an Ultra Cycling Race: A Mixed-Method Case Report.

In faculties of health sciences, almost 30% of nursing students exercise less than once a week. This mixed-method case report presents the 38-month evolution of the physiological and psychological health parameters of a sedentary and physically inactive nursing student. During this period, she first took part in a one-semester institutional physical activity (PA) program that was offered by her university before being selected for participation in the Race Across America (RAAM) with a university relay team. In the four months leading up to the RAAM, she followed a cycling training program. After the RAAM, she was followed-up for the next 28 months. The results showed that each phase of the study had an important impact on the subject and showed that sedentary and physical inactive behaviours are reversible. Institutional PA programs, including training education in addition to concurrent strength and endurance training, can lead to physiological and psychological health improvements. For some individuals, participating in an athletic challenge can improve motivation and long-term adherence to PA participation. An individualised approach should be considered in future interventions that aim to promote PA participation. In the specific context of a university of health sciences, this kind of initiative could positively influence the general population's health by empowering students to become role models towards PA promotion.

The fatigue-induced alteration in postural control is larger in hypobaric than in normobaric hypoxia.

To test the hypothesis that postural control would be more affected by plantar flexors fatigue during acute exposure in hypobaric (HH) than in normobaric (NH) hypoxia or normobaric normoxia (NN). Twelve young male adults performed in a random order three experimental sessions (in HH and NH (FiO2 0.139) at an altitude of 2950 m, and in NN at 500 m) composed of a bipedal postural control with eyes open on a posturographic platform before and after a plantar flexors fatiguing protocol. Center of pressure (CoP) trajectory and stabilogramm diffusion analyses (SDA) parameters were assessed. A two-way repeated measures analysis of variance was used to identify differences by examination of the group and time interaction. Surface of CoP trajectory analysis, increased at POST in HH (p < 0.001) and in NH (p < 0.01) compared to NN. SDA confirmed that PC was more altered in HH than in NH (p < 0.001) and NN (p < 0.05) at POST. The plantar flexor fatigue-induced alteration in postural control increased to a larger extent in HH than in NH or NN, suggesting an alleviating influence of the decreased barometric pressure per se and a mechanical influence of the higher breathing frequency in HH.

Changes in spatio-temporal gait parameters and vertical speed during an extreme mountain ultra-marathon.

The aim of the present study was to investigate the effects of altitude and distance on uphill vertical speed (VS) and the main spatio-temporal gait parameters during an extreme mountain ultra-marathon. The VS, stride height (SH) and stride frequency (SF) of 27 runners were measured with an inertial sensor at the shank for two different altitude ranges (low 1300-2000 m vs high 2400-3200 m) of 10 mountains passes distributed over a 220 km course. There was a significant interaction (F(4,52) = 4.04, p < 0.01) for the effect of altitude and distance on VS. During the first passes, the mean VS was faster at lower altitudes, but this difference disappeared at a quarter of the race length, suggesting that neuromuscular fatigue influenced the uphill velocity to a larger extent than the oxygen delivery. The average VS, SH and SF were 547 ± 135 m/h, 0.23 ± 0.05 m and 0.66 ± 0.09 Hz. The individual VS change for each uphill portions was more strongly correlated with the changes in SH (r = 0.80, P < 0.001, n = 321) than SF (r = 0.43, P < 0.001, n = 321). This suggests a large effect of the knee extensors strength loss on the diminution of VS.

Running from Paris to Beijing: biomechanical and physiological consequences.

The purpose of this study was to examine the physiological and biomechanical changes occurring in a subject after running 8,500 km in 161 days (i.e. 52.8 km daily). Three weeks before, 3 weeks after (POST) and 5 months after (POST+5) running from Paris to Beijing, energy cost of running (Cr), knee flexor and extensor isokinetic strength and biomechanical parameters (using a treadmill dynamometer) at different velocities were assessed in an experienced ultra-runner. At POST, there was a tendency toward a 'smoother' running pattern, as shown by (a) a higher stride frequency and duty factor, and a reduced aerial time without a change in contact time, (b) a lower maximal vertical force and loading rate at impact and (c) a decrease in both potential and kinetic energy changes at each step. This was associated with a detrimental effect on Cr (+6.2%) and a loss of strength at all angular velocities for both knee flexors and extensors. At POST+5, the subject returned to his original running patterns at low but not at high speeds and maximal strength remained reduced at low angular velocities (i.e. at high levels of force). It is suggested that the running pattern changes observed in the present study were a strategy adopted by the subject to reduce the deleterious effects of long distance running. However, the running pattern changes could partly be linked to the decrease in maximal strength.

Participating In The Race Across AMerica In A Team Of Eight Cyclists: Do Not Neglect Crew Preparation.

BACKGROUND: The Race Across AMerica (RAAM) is considered as one of the longest, and most difficult cycling races in the world. It can be performed in solo or in relay of two, four or eight persons. PURPOSE/METHOD: The aim of the present study was to investigate several physiological, perceptual and psychological responses before, during and after RAAM in a team of eight amateur cyclists. Because logistics of all team is demanding and complex, crew members have followed the same testing procedure. RESULTS: The main result is that parameters were globally not altered to a greater extent in cyclists than in crew members over the course of the RAAM, and that all variables returned to pre-race levels 1 week after the end of the race in both groups. In crew, body fat was decreased (p < 0.05) at mid-race (Mid) vs 1 week before the RAAM (Pre) (-1.5%) and total body water was increased (p < 0.05) at Mid vs Pre (+2.5%). In pre-relay quadriceps strength in cyclists was significantly lower (p < 0.05) at Mid vs Pre (41.6 ± 9.1 vs 45.0 ± 11.2 N, d = 0.36). Therefore, performing the race with eight well-prepared amateur cyclists seems to decrease potential risks on health. In crew, quadriceps strength remained stable at each assessment time but general fatigue increased all along the race. Anger was increased (p < 0.05) at Mid vs Pre in crew. CONCLUSION: The most important message of this study is that crew members for a team of eight require adequate and sufficient preparation and training. Roles and responsibilities need to be thoroughly defined; individuals need to know each other beforehand and they must be prepared for sleep deprivation. The results of this study show the importance of the preparation of two teams: crew members, as well as cyclists.

Postural Control Follows a Bi-Phasic Alteration Pattern During Mountain Ultra-Marathon.

It is well knows that postural control (PC) is deteriorated with neuromuscular fatigue, altitude or sleep deprivation induced by a mountain ultra-marathon (MUM). Several regulatory mechanisms have also been reported during this type of event and the changes in PC at different points of MUM remain unknown. The purpose of this study was to investigate the time course of PC during an extreme MUM. We tested the hypothesis that PC alteration would not increase linearly. Methods: 16 participants (age 45.1 ± 9.6 years) were tested bipedaly on a posturographic platform for 51.2 s with eyes open every ∼50 km. Both traditional and stabilogram diffusion analyses (SDA) were performed. A visual analog scale (VAS) was used for a subjective evaluation of global fatigue, sleep feeling and pain. Results: The main parameters (center of pressure trajectory analysis) increased significantly (p < 0.001, d = 1.56, very large) until km 100. This was confirmed by SDA in the antero-posterior plane. Short term effective diffusion coefficient significantly increased (p < 0.001, d = 1.07, very large) as critical point (p < 0.01, d = 1.57, very large). From km 100 to 200, a different response was observed with a continuous decrease in most of the PC parameters. This was confirmed by SDA in the antero-posterior plane. Short term effective diffusion coefficient significantly increased (p < 0.001, d = 1.39, very large) as critical point (p < 0.01, d = 1.51, very large). Conclusion: Posture alteration is progressively increased until 100 km. After this point, compensatory mechanisms appear to limit the posture degradation. This bi-phasic response is of interest for better understanding the coping with extreme fatigue.

Enhancement of isokinetic muscle strength with a combined training programme in chronic heart failure.

BACKGROUND: Patients with congestive heart failure (CHF) exhibit an impaired exercised tolerance that dramatically limits their functional capacity and alters their quality of life. DESIGN: The aim of this study was to compare the effects of two types of training programmes on isokinetic muscle strength and aerobic capacities in patients with CHF. METHODS: A group of 23 stable CHF patients included consecutively followed an exercise training programme, 3 days a week for 8 weeks. The first group (P1, n=11) exercised on a cycloergometer for 45 min at 65% of peak VO2. The second group (P2, n=12) followed a 45-min combined bicycle and quadricipital strength training. Strength training consisted of 10 series of 10 repetitions at 70% of maximal voluntary force. Incremental maximal cardiopulmonary exercise tests as well as an isokinetic quadricipital dynamometry evaluation were performed before and after training. RESULTS AND CONCLUSIONS: In P1, peak VO2 increased by 20% (22.3+/-4.9 versus 17.8+/-4.5 ml min(-1) kg(-1); P<0.05) without any significant change in isokinetic muscle strength. In P2, peak VO2 improved within the same range (20.5+/-2.8 versus 18.6+/-3.7 ml min(-1) kg(-1); P<0.01). This last rehabilitation programme significantly increased isokinetic muscle strength at each angular velocities (+10.5+/-13.5%, P<0.04; +5.6+/-7.0%, P<0.03; for 180 degrees s(-1) and 60 degrees s(-1) respectively). Only the combined endurance/strength training programme was associated with an improvement in both peak VO2 and peripheral muscle strength, two significant parameters of outcome and quality of life in CHF.

Assessment of evertor weakness in patients with chronic ankle instability: Functional versus isokinetic testing.

BACKGROUND: Ankle sprain is the most common sport-related injury and eccentric weakness of ankle evertors is regarded as a significant muscular deficit related to chronic ankle instability. However, the eccentric performance of the evertors is rarely assessed by clinicians because procedures used for research purposes (i.e. isokinetic tests) are not easily applicable in daily practice. METHODS: The present study assessed the ability of two different testing procedures to distinguish between groups of 12 healthy subjects or 12 patients suffering from chronic ankle instability. On the one hand, the strength of evertors was assessed with a goldstandard isokinetic procedure. On the other hand, we assessed the ability of the subjects to control ankle inversion during weight bearing (functional standing test). FINDINGS: Data showed no significant difference between groups for isokinetic peak torque values normalized to body weight. Conversely, the functional test revealed a significantly impaired ability to control ankle inversion during weight bearing in subjects with chronic ankle instability. INTERPRETATION: This suggests that this easy-to-apply functional test is better suited compared to isokinetic testing procedures to assess weakness of evertors in patients suffering from chronic ankle instability. Moreover, this test may also be used to objectively monitor improvements during rehabilitation or progression in prevention protocols.

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 world's 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 ([Formula: see text]) 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: Subject's [Formula: see text] was 48.1 mL·kg-1·min-1. Throughout the six uphills investigated the mean exercise intensity was 57.3 ± 6.0% [Formula: see text] 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·[Formula: see text], 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.

Modulations of human autonomic function induced by positive pressure-assisted breathing.

In order to examine the acute autonomic response in humans during and immediately after positive pressure-assisted (PPA) breathing, spontaneous cardiac baroreflex (BR) sensitivity was studied through the adaptation of consecutive RR intervals in response to spontaneous systolic blood pressure fluctuations in 11 healthy subjects. The gain (alpha-index) in baroreceptor reflex was estimated using cross-spectral analysis (RR interval variability and systolic blood pressure variability) for the low frequency (LF) and high frequency (HF) bands. All measurements were made under fixed breathing rate (12 breaths per minute), and realized consecutively at baseline level (20 min), after-short inspiratory pressure support plus positive end-expiratory airway pressure (IPS + PEEP) ventilation (15 min), again under normal conditions (20 min; recovery period) and, finally, during a standard upward orthostatic challenge test (15 min; orthostatic challenge). The spontaneous BR gain in the HF band increases slightly during ventilation (+26.1 +/- 11.7%, P<0.05) and decreases significantly during recovery without any significant alteration in mean heart rate, systolic or diastolic blood pressure. The spontaneous BR gain in the LF band decreases during IPS + PEEP ventilation (8.4 +/- 4.4 versus 12.7 +/- 6.2 ms mm(-1) Hg; P<0.05) and returns to basal level during recovery. Orthostatic challenge altered significantly the BR gain in both HF and LF bands with significant heart rate acceleration. In humans, while the parasympathetic control of heart rate and blood pressure is found moderately enhanced, the sympathetic BR drive appears significantly and transitory altered under short term IPS + PEEP ventilation with a degree of alteration comparable to those observed during orthostatic challenge.

Hamstring Architectural and Functional Adaptations Following Long vs. Short Muscle Length Eccentric Training.

Most common preventive eccentric-based exercises, such as Nordic hamstring do not include any hip flexion. So, the elongation stress reached is lower than during the late swing phase of sprinting. The aim of this study was to assess the evolution of hamstring architectural (fascicle length and pennation angle) and functional (concentric and eccentric optimum angles and concentric and eccentric peak torques) parameters following a 3-week eccentric resistance program performed at long (LML) vs. short muscle length (SML). Both groups performed eight sessions of 3-5 × 8 slow maximal eccentric knee extensions on an isokinetic dynamometer: the SML group at 0° and the LML group at 80° of hip flexion. Architectural parameters were measured using ultrasound imaging and functional parameters using the isokinetic dynamometer. The fascicle length increased by 4.9% (p < 0.01, medium effect size) in the SML and by 9.3% (p < 0.001, large effect size) in the LML group. The pennation angle did not change (p = 0.83) in the SML and tended to decrease by 0.7° (p = 0.09, small effect size) in the LML group. The concentric optimum angle tended to decrease by 8.8° (p = 0.09, medium effect size) in the SML and by 17.3° (p < 0.01, large effect size) in the LML group. The eccentric optimum angle did not change (p = 0.19, small effect size) in the SML and tended to decrease by 10.7° (p = 0.06, medium effect size) in the LML group. The concentric peak torque did not change in the SML (p = 0.37) and the LML (p = 0.23) groups, whereas eccentric peak torque increased by 12.9% (p < 0.01, small effect size) and 17.9% (p < 0.001, small effect size) in the SML and the LML group, respectively. No group-by-time interaction was found for any parameters. A correlation was found between the training-induced change in fascicle length and the change in concentric optimum angle (r = -0.57, p < 0.01). These results suggest that performing eccentric exercises lead to several architectural and functional adaptations. However, further investigations are required to confirm the hypothesis that performing eccentric exercises at LML may lead to greater adaptations than a similar training performed at SML.