1,721,044 research outputs found
High-intensity decreasing interval training (HIDIT) increases time above 90% V ̇ O2peak
Full text linkPurpose: Training near V ̇ O2max is considered to be the most effective way to enhance V ̇ O2max. High-intensity interval training (HIIT) is a well-known time-efficient training method for improving cardiorespiratory and metabolic function and V ̇ O2max. While long HIIT bouts allow V ̇ O2max to be achieved quickly, short HIIT bouts improve time to exhaustion (Tlim). The aim of this study was to evaluate the time spent above 90% V ̇ O2peak (T > 90% V ̇ O2peak) during three different HIIT protocols. Methods: Twelve cyclists performed three HIIT sessions. Each protocol had the same work and recovery power and ratio of work·recovery−1. The protocols consisted of long-interval HIIT (LIHIIT, 3 min work—2 min recovery), short-interval HIIT (SIHIIT, 30 s work—20 s recovery), and high-intensity decreasing interval training (HIDIT, work from 3 min to 30 s and recovery from 2 min to 20 s). T > 90% V ̇ O2peak, Tlim, blood lactate [La], and rate of perceived exertion (RPE) were measured at Tlim. Results: T > 90% V ̇ O2peak was greater in HIDIT (312 ± 207 s) than in SIHIIT (182 ± 225 s; P = 0.036) or LIHIIT (179 ± 145 s; P = 0.027). Tlim was not significantly different (P > 0.05) between HIDIT (798 ± 185 s), SIHIIT (714 ± 265 s), and LIHIIT (664 ± 282). At Tlim, no differences in [La] and RPE were found between protocols (P > 0.05). Conclusion: HIDIT showed the highest T > 90% V ̇ O2peak, suggesting that it may be a good strategy to increase time close to V ̇ O2peak, despite similar Tlim, [La], and RPE at Tlim
Muscle damage and inflammatory status biomarkers after a 3-stage trail running race
No full textBacKGround: participants in ultramarathon and multi-stage races are continuously increasing. a detailed knowledge of the time-course of the restoration in muscular, cardiac, and inflammatory biomarkers after a multi-stage race may help the design of training schedules focused to avoid adverse outcomes of repetitive high-intensity endurance exercise and athlete exhaustion. Thus, the aim of the study was to evaluate blood parameters and serum biomarkers associated to muscle damage and inflammation in athletes participating in a 3-stage competition. MeThodS: Ten runners concluded the race “Magraid” consisting of 3 stages of 22, 48 and 20 km. Before (pre), immediately after the end of the third stage (POST) and five days after the last stage (R5d), we collected blood samples. RESULTS: Among others, at POST mean white blood cell (+57±42%; P=0.006), blood urea nitrogen (+68±39%; P<0.001), creatinine (+17±12%, P=0.005), alanine aminotransferase (ALT, +104±69%; P=0.002), lactate dehydrogenase (LDH, +116±64%; P<0.001), creatine kinase (CK, +2044±1433%; P=0.011), CK-MBm (+1544±1007%; P=0.004), cardiac troponin I (cTnI, +85±129%; P=0.015), C-reactive protein (hsCRP, +2137±1660%; P=0.015) were higher than PRE. At R5d, ALT (+72±53%; P=0.010), LDH (+32±25%; P=0.006) and hsCRP (+252±234%; P=0.021) were still different compared with PRE. CONCLUSIONS: A 3-stage trail running race induces an inflammatory status and muscle damage and functional consequences on some physiological systems that may not be completely recovered within a short period
High-intensity interval training: optimizing oxygen consumption and time to exhaustion taking advantage of the exponential reconstitution behaviour of D’
Full text linkPurpose: Accumulating the time near maximum aerobic power (V ̇ O 2max) is considered to be the most effective way to improve aerobic capacity. The aims of this study were: (1) to verify whether postponing the first recovery interval improves time to exhaustion during a high-intensity interval training (HIIT) test, and (2) to verify whether a HIIT protocol with decreasing interval duration (HIDIT) is more effective in accumulating time near V ̇ O 2max compared with two classical protocols with short intervals (SIHIIT) and long intervals (LIHIIT). Methods: Nine active males (35 ± 11 years, V ̇ O 2max 52 ± 5 mL·min−1·kg−1) performed a graded exercise test on an athletic track. Critical velocity and D’ were estimated from three to five high-intensity trials to exhaustion. Then, the subjects performed three trials with a single recovery interval after 30 s (Rec30s), after 3 min (Rec3min) and after exhaustion (RecTlim) to verify whether postponing the first recovery interval enhances the time to exhaustion. Finally, the subjects performed the three HIIT protocols mentioned above. Results: The time to exhaustion was significantly greater in RecTlim (464 ± 67 s) than in Rec3min (388 ± 48 s) (p 0.0001). Additionally, it was significantly greater in Rec3min than in Rec30s (p = 0.0247). Furthermore, the time accumulated near V ̇ O 2max was significantly longer in HIDIT (998 ± 129 s) than in SIHIIT (678 ± 116 s) (p = 0.003) and LIHIIT (673 ± 115 s) (p < 0.031). Conclusions: During the trials, postponing the first recovery interval was effective in improving the time to exhaustion. Moreover, HIDIT was effective in prolonging the time near V ̇ O 2max
Effects of gravitational versus iso-inertial resistance training on leg muscle force and metabolic cost of walking in healthy older adults
No full textBACKGROUND: The purpose was to compare the effects of 8-week resistance training programs (flywheel iso-inertial [FW] versus traditional gravity-dependent resistance training [GD]) performed twice a week at the same rate of perceived exertion (RPE), on muscle force and power capacities and physical performance in healthy older participants. METHODS: Twenty-four participants were randomly assigned to either FW (male/female ratio: 7/5, age: 67.1±3.8 years) or GD (male/female ratio: 6/6, age 68.3±3.0 years) group. Knee extension maximal isometric voluntary contractions (MVC), lower limb maximal explosive power (MEP), Six-Minute Walking Test (6MWT), Timed Up-and-Go Test (TUG), metabolic cost of walking (CW) and agonist-antagonist co-contraction time (CCT) during walking were evaluated before and after training. RESULTS: absolute MEP and MEP normalized for body mass increased only in FW than GD group (+10.8% vs. +0.31%, P=0.056, respectively; +14.8% vs. +13.9%, P<0.001, respectively). Both training modalities improved MVC to a similar extent (+11.1% in FW vs. +13.4% in GD, P<0.001). Analogously, 6MWT distance increased in FW and GD (+5.2 and +5.5%, P<0.041, respectively). No effects of time and training modality were observed on the other parameters. CONCLUSIONS: The results of this study suggest that when FW and GD are administered at the same RPE with FW performed at higher movement speed in the concentric phase, both the trainings generate similar improvements in muscle strength but only the former can promote greater muscle power enhancements than GDin healthy older adults
Effects of NMES-elicited versus voluntary low-level conditioning contractions on explosive knee extensions
No full textObjectives: Electrically-induced or voluntary conditioning-contractions (CC) can be used to affect contractile properties of a subsequent explosive contraction (EC). Here, we aimed at comparing the effect of neuromuscular-electrical-stimulation (NMES) vs voluntary CC performed prior to explosive contractions of the knee extensors. Methods: A 10 sec NMES CC (100Hz, 1000μs, 10% MVC), or a voluntary contraction (VOL CC) mimicking the NMES CC, preceded an isometric EC of the knee extensors. Explosive contraction was performed with the goal to reach the target (70% MVC) as quickly as possible. Results: All the parameters related with the explosive contractions’ muscle-output were similar between protocols (difference ranging from 0.23%, Mean Torque; to 5.8%, Time to Target), except for the Time to Peak Torque, which was lower when preceded by NMES (11.1%, p=0.019). Interestingly, the RTD 0–50 ms_EC was 37.3% higher after the NMES compared with the VOL CC protocol. Conclusion: Explosive contraction was potentiated by an NMES CC as compared with a voluntary CC. This may be due to a reduction in descending drive following VOL CC, which has been shown to occur even with low-level voluntary efforts. These findings could be used to improve rehabilitation or training protocols that include conditioning contractions
Walking versus cycling test: Physiological responses in normobaric hypoxia
No full textBACKGROUND: Races that take place in the mountains cover a variety of terrains at several altitudes. Atest for predicting acute mountain sickness has been developed on the basis of a "normal" population but not on the basis of an athlete population. The aim of this study was to compare the Richalet Test to a specific test for athletes. METHODS: Eleven subjects (age: 29.7±8.9 years, VO2peak: 55.7±8.5 mL/kg/min) underwent two incremental tests on a cycle ergometer (CE) and treadmill (TR). Then, they underwent two tests on the CE and TR composed of: 1) five minutes of rest in normoxia; 2) five minutes of rest in hypoxia (fraction of inspired oxygen (11.5%); 3) five minutes of walking or cycling at an intensity of 80% of the respiratory compensation point in hypoxia; and 4) five minutes of rest in normoxia. We compared the following parameters at rest and during exercise: Desaturation, ventilatory and cardiac response. RESULTS: None of the mean values of the investigated parameters differed between the two tests (P>0.05), but some subjects who had out-of-range values on the CEdid not have out-of-range values on the TR(or vice versa). CONCLUSIONS: We showed that there were: 1) no differences in the mean values of the analyzed parameters between the two protocols; and 2) that the responses to the CEand TRprotocols varied across individuals. For individuals who are planning to hike or run at a high altitude they should undergo a walking test. Additionally, when athletes plan to compete at high altitudes, the intensity of the test should be similar to that planned for the race
Energetics of shuttle runs: the effects of distance and change of direction.
No full textShuttle runs can be used to study the physiological responses in sports (such as basketball) characterized by sprints (accelerations/decelerations) and changes of direction.
Purpose: To determine the energy cost (C) of shuttle runs with different turning angles and over different distances (with different acceleration/deceleration patterns).
Methods: Nine basketball players were asked to complete 6 intermittent tests over different distances (5, 10, 25 m) and with different changes of direction (180° at 5 and 25 m; 0°, 45°, 90°, and 180° at 10 m) at maximal speed (v ≈ 4.5 m/s), each composed by 10 shuttle runs of 10-s duration and 30-s recovery; during these runs oxygen uptake (VO2), blood lactate (Lab), and C were determined.
Results: For a given shuttle distance (10 m) no major differences where observed in VO2 (~33 mL · min–1 · kg–1), Lab (~3.75 mM), and C (~21.2 J · m–1 · kg–1) when the shuttle runs were performed with different turning angles. For a given turning angle (180°), VO2 and Lab were found to increase with the distance covered (VO2 from 26 to 35 mL · min–1 · kg–1; Lab from 0.7 to 7.6 mM) while C was found to decrease with it (from 29.9 to 10.6 J · m–1 · kg–1); the relationship between C and d (m) is well described by C = 92.99 × d0.656, R2 = .971. Conclusions: The metabolic demands of shuttle tests run at maximal speeds can be estimated based on the running distance, while the turning angle plays a minor role in determining C
Predictive factors of responsiveness to a body weight reduction program in Prader–Willi patients at 6 years of follow-up
Full text linkPrader–Willi syndrome (PWS), a multisystemic disorder caused by lack of expression of genes on the paternally inherited chromosome 15q11.2-q13 region, is characterized by hyperphagia and childhood-onset morbid obesity, A retrospective cohort study of 60 PWS patients, 38 females and 22 males, undergoing a 6-year rehabilitation program was analysed. Mean age at the time of first admission was 27 ± 7 years, body weight (BW) was 97 kg ± 29 kg and height was 1.53 ± 0.09 m. Twenty-four patients (40%) showed BW loss after 6 years of follow-up, seventeen (28%) remained stable and nineteen (32%) gained BW. Responsiveness in term of BW reduction was less frequent in patients with the UPD karyotype, karyotype del15 being more frequent among responsive patients. Furthermore, responsive PWS subjects had a higher BMI (47 vs. 36 kg/m2), waist (123 vs. 106 cm) and hip (136 vs. 118 cm) circumferences than non-responsive at the time of first hospitalization. Baseline body composition and metabolic parameters did not differentiate between responsive and non-responsive patients. Given the rarity of PWS and relative lack of studies, these results can be considered relevant because based on a relatively large number of PWS patients followed up for a long term period
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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