DECELERATION COUNTS: ESTIMATING THE ENERGY COST OF SHUlTLE RUNNING FROM MECHANICAL WORK

To estimate the energetic requirements of 5-m shuttle running based on kinematic data, we devised a modified version of existing models for the estimation of the energy cost of gait. In our approach, negative/eccentric work during deceleration phases was added to positive/concentric work in propulsive phases. Ten subjects performed two 5-rnin trials at 50% and 75% of their maximal aerobic speed. The metabolic cost estimated from 30 kinematics was compared to that measured by a portable metabolimeter. The estimation error was 1.2 J/kg/s (7.3%): results encourage to apply this method for the estimation of the workload in sports involving frequent turns and changes of direction

A KINEMATICALLY BASED ALGORITHM TO ESTIMATE THE ENERGY COST OF VARIABLE-SPEED SHUTTLE RUNNING

Changes of direction (CoDs) have a high metabolic and mechanical impact in field and court team sports, but the estimation of the associated workload is still inaccurate. The aim of this study is to establish a kinematic-based algorithm to determine the energy cost of running at variable speed with frequent 180° CoDs. Kinematic and metabolic data were simultaneously collected during 5-minutes 5+5 m shuttle run tests. Mechanical work computation was split into positive (eccentric) and negative (concentric) contributions. When compared to the actual energy cost, the estimation algorithm returned an error of 5%. This model constitutes the theoretical basis to extend the model from the laboratory to the field, obtaining an accurate measure of the workload of training and matches

On-sight and red-point climbing: changes in performance and route-finding ability in male advanced climbers

Aim: In lead climbing, the ascent of the route can be defined as on-sight or red-point. On-sight is the more challenging style since it demands greater physiological and psychological commitment. The differences between the two modes in advanced climbers have not been studied much. Two essential skills needed to optimize performance, in both on-sight and in red-point climbing, are route interpretation (RI) ability and movements sequence recall. Therefore, this study aimed to compare performance between on-sight and red-point ascent in advanced climbers and evaluate how a climber’s RI ability and movement sequences recall might change before and after on-sight and red-point climbing. Methods: Eighteen advanced male climbers (age 29.2 ± 4.7 years, body mass 67.8 ± 3.6 kg, stature 175.2 ± 2.4 cm, best red-point and on-sight grades 7b+/8a and 7a+/7b+, respectively) were video-recorded during the route ascent in on-sight and red-point modes to evaluate performance and to measure static and dynamic action times. RI ability and movement sequence recall were assessed before and after each climb. Level of anxiety was evaluated via a self-report questionnaire. Heart rate (fH), lactate concentration, ([La–]), and rating of perceived exertion (RPE) were detected during and after each climb. Results: Compared to on-sight, an improvement in performance was observed in a red-point climb: the ascent was faster (148.7 ± 13.6 s and 179.5 ± 12.5 s, respectively, P < 0.05), smoother (significant reduction in exploratory moves and in stops times, P < 0.05), less demanding physiologically (lower fHpeak and [La–]peak, P < 0.05), and psychologically (lower RPE, cognitive and somatic anxiety and higher self-confidence, P < 0.05). The RI ability was improved in red-point versus on-sight and, in the same mode, between pre and post ascent. Conclusion: Red-point climbing was found to be less demanding than on-sight, both physiologically and psychologically, under the conditions investigated by this study. Our findings suggest that RI is a trainable skill and underscore the importance of including specific techniques in training programs designed to improve interaction between perceptual, psychological, and physiological factors

Cardiorespiratory and Metabolic Responses to Sinusoidal Exercise of Moderate Intensity: Reliability of the Measurements and the Effects of Fatigue

The cardiorespiratory and metabolic responses to sinusoidal exercise, in which work rate follows an oscillating pattern, have been proposed to assess the effectiveness of the cardiorespiratory adjustments. The repetition of successive sinusoidal periods permits to simultaneously reduce the influence of random fluctuations and accentuate the underlying physiological response. Data analysis has been often performed by overlapping and averaging successive cycles assuming no differences among them, thus excluding the possible presence of fatigue throughout successive cycles. After assessing the reliability of the measurements during sinusoidal exercise, this study sought to investigate the possible differences among subsequent cycles of sinusoidal work. Eleven active volunteers (age: 28±6 yrs., body mass: 73±7 kg; stature: 1.79±0.06 m, maximum oxygen uptake (VO2max): 52 ml·kg−1·min−1) participated to the study that was conducted in accordance with the Basic Principles of the Declaration of Helsinki. After determining individual VO2max and critical power (CP) on a cycle ergometer, they underwent sinusoidal work rates characterized by an amplitude (A), a midpoint (MP) and a period equal to ±50W, 50W below CP and 240s, respectively, up to exhaustion. On a different day, participants repeated the same experimental session for reliability purposes. Expiratory ventilation (VE), oxygen uptake (VO2), carbon dioxide output (VCO2), and heart rate (fH) responses were fitted by the sinewave function that minimized the residuals. A, MP and the time-delay (tD, the latency between mechanical work rate and physiological responses) of all parameters were determined for each cycle. Reliability assessment between day 1 and 2 was expressed as Cronbach’s a and intraclass correlation coefficient (ICC). A one-way ANOVA for repeated measures tested the presence of differences among cycles. Regression analysis was also applied to explore possible relationship between each variables and time. Reliability analysis revealed a very high to high ICC values for most of the parameters, with the exception of A for VO2 and VCO2 and tD for fH (moderate reliability). A of VE and fH response increased and decreased with time, respectively (p<0.05). MP of VE and fH showed a positive regression that led to significantly higher values in the last compared to the first cycle; on the contrary, no changes were observed among cycles in all other MP data. tD was similar in each cycle for all the investigated parameters despite a very slight negative regression found for VCO2. In conclusion, most of the physiological responses to moderate sinusoidal exercise exhibited a high to very high reliability. Some of the cardiorespiratory parameters showed significant changes with time throughout the sinusoidal exercise possibly due to the onset of fatigue. Therefore, an approach that overlaps and averages all the cycles together should not be performed to avoid wrong estimation of physiological responses to sinusoidal exercise, unless the averaging approach involves only the first cycles

Possible predictors of involuntary weight loss in patients with Alzheimer's disease

Loss in body mass (∆BM) is a common feature in patients with Alzheimer's disease (AD). However, the etiology of this phenomenon is unclear. The aim of this cohort study was to observe possible ∆BM in AD patients following a standard institutionalized diet. Secondary objective was to identify possible predictors of ∆BM. To this end, 85 AD patients (age: 76±4 yrs; stature: 165±3 cm; BM: 61.6±7.4 kg; mean±standard deviation) and 86 controls (CTRL; age: 78±5 yrs; stature: 166±4 cm; BM: 61.7±6.4 kg) were followed during one year of standard institutionalized diet (~1800 kcal/24h). BM, daily energy expenditure, albuminemia, number of medications taken, and cortisolism, were recorded PRE and POST the observation period. Potential predictors of ∆BM in women (W) and men (M) with AD were calculated with a forward stepwise regression model. After one year of standard institutionalized diet, BM decreased significantly in AD (-2.5 kg; p < 0.01), while in CTRL remained unchanged (-0.4 kg; p = 0.8). AD patients and CTRL exhibited similar levels of daily energy expenditure (~1625 kcal/24h). The combination of three factors, number of medications taken, albuminemia, and cortisolism, predicted ∆BM in W with AD. At contrary, the best predictor of ∆BM in M with AD was the cortisolism. Despite a controlled energy intake and similar energy expenditure, both W and M with AD suffered of ∆BM. Therefore, controlled diet did not prevent this phenomenon. The assessments of these variables may predict W and M with AD at risk of weight loss

Reliability of the Electromechanical Delay Components Assessment during the Relaxation Phase

The study aimed to assess by an electromyographic (EMG), mechanomyographic (MMG), and force-combined approach the electrochemical and mechanical components of the overall electromechanical delay during relaxation (R-EMD). Reliability of the measurements was also assessed. To this purpose, supramaximal tetanic stimulations (50 Hz) were delivered to the gastrocnemius medialis muscle of 17 participants. During stimulations, the EMG, MMG, and force signals were detected, and the time lag between EMG cessation and the beginning of force decay (Δt EMG-F, as temporal indicators of the electrochemical events) and from the initial force decrease to the largest negative peak of MMG signal during relaxation (Δt F-MMG, as temporal indicators of the mechanical events) was calculated, together with overall R-EMD duration (from EMG cessation to the largest MMG negative peak during relaxation). Peak force (pF), half relaxation time (HRT), and MMG peak-to-peak during the relaxation phase (R-MMG p-p) were also calculated. Test-retest reliability was assessed by Intraclass Correlation Coefficient (ICC). With a total R-EMD duration of 96.9 ± 1.9 ms, Δt EMG-F contributed for about 24% (23.4 ± 2.7 ms) while Δt F-MMG for about 76% (73.5 ± 3.2 ms). Reliability of the measurements was high for all variables. Our findings show that the main contributor to R-EMD is represented by the mechanical components (series elastic components and muscle fibres behaviour), with a high reliability level for this type of approach

Heart rate response to different training phases in young female acrosport athletes

Background Acrosport is a specific type of gymnastics executed in pairs or groups of athletes, characterized by static, acrobatic, and choreographic elements. Very few data are available in the literature on the physiological profile of acrosport athletes. Purpose The aim of the study was to evaluate the heart rate (HR) response to the different phases of a typical acrosport training session. Methods Twenty female acrosport athletes (13 bases and 7 tops) volunteered for the study. To assess the cardio- vascular commitment and the percentage of HR utilized, data were averaged during the entire training session and for each training phase. Was calculated also the percentage of HR reserve for each training phase. Results HR response showed a statistical difference among the different training phases in both base and top athletes. Moreover, bases and tops had a significantly dif- ferent HR response only in the individual phases. Conclusion The training phases during a typical acrosport training session revealed a different cardiovascular com- mitment during exercise. Differences between tops and bases were also retrieved and were probably due to the different level of experience and the different role played by tops and bases during the same combination of exercises

Effect of respiratory muscle training on maximum aerobic power in normoxia and hypoxia

To assess the effects of respiratory muscle training (RMT) on maximum oxygen uptake (VO2max) in normoxia and hypoxia, 9 healthy males (age 24 +/- 4 years; stature 1.75 +/- 0.08 m; body mass 72 +/- 9 kg; mean +/- SD) performed on different days maximal incremental tests on a cycle ergometer in normoxia and normobaric hypoxia (FIO2=0.11), before and after 8 weeks of RMT (5 days/week). During each test, gas exchange variables were measured breath-by-breath by a metabolimeter. After RMT, no changes in cardiorespiratory and metabolic variables were detected at maximal exercise in normoxia. On the contrary, in hypoxia expired and alveolar ventilation (V(E(and V(A), respectively) at maximal exercise were significantly higher than pre-training condition (+12 and +13%, respectively; P < 0.05). Accordingly, alveolar O2 partial pressure (PAO2) after RMT significantly increased by approximately 10%. Nevertheless, arterial PO2 and VO2max did not change with respect to pre-training condition. In conclusion, RMT improved respiratory function but did not have any effect on VO2max, neither under normoxic nor hypoxic condition. In hypoxia, the significant increase in V(E) and V(A) at maximum exercise after training lead to higher alveolar but not arterial PO2 values, revealing an increased A-a gradient. This result, according to the theoretical models of VO2max limitation, seems to contradict the lack of VO2max increase in hypoxia, suggesting a possible role of increased ventilation-perfusion mismatch