Synergistic difference in the effect of stretching on electromechanical delay components.

This study investigated the synergistic difference in the effect of stretching on electromechanical delay (EMD) and its components, using a simultaneous recording of electromyographic, mechanomyographic, and force signals. Twenty-six healthy men underwent plantar flexors passive stretching. Before and after stretching, the electrochemical and mechanical components of the EMD and the relaxation EMD (R-EMD) were calculated in gastrocnemius medialis (GM), lateralis (GL) and soleus (SOL) during a supramaximal motor point stimulation. Additionally, joint passive stiffness was assessed. At baseline, the mechanical components of EMD and R-EMD were longer in GM and GL than SOL (Cohen's d from 1.78 to 3.67). Stretching decreased joint passive stiffness [-22(8)%, d = -1.96] while overall lengthened the electrochemical and mechanical EMD. The mechanical R-EMD components were affected more in GM [21(2)%] and GL [22(2)%] than SOL [12(1)%], with d ranging from 0.63 to 1.81. Negative correlations between joint passive stiffness with EMD and R-EMD mechanical components were found before and after stretching in all muscles (r from -0.477 to -0.926; P from 0.007 to <0.001). These results suggest that stretching plantar flexors affected GM and GL more than SOL. Future research should calculate EMD and R-EMD to further investigate the mechanical adaptations induced by passive stretching in synergistic muscles.

Acute carnosine and ß-alanine supplementation increase the compensated part of the ventilation versus work rate relationship during a ramp incremental cycle test in physically active men.

BACKGROUND: Chronic supplementation with carnosine and ß-alanine (Carn-ßA) has been proposed to improve muscle contractility and reduce muscle fatigue mainly through an increase in intracellular pH buffering capacity. However, the acute ergogenic effects of Carn-ßA supplementation are poorly investigated. This study aimed at evaluating the acute effects of a single Carn-ßA supplementation on the cardiorespiratory and metabolic response during a ramp cycle-ergometric test. METHODS: This randomized, double-blind, placebo-controlled study, involved 10 healthy males (age: 22.2±1.9 years, body mass: 72.5±7.9 kg, stature: 1.72±0.08 m, Body Mass Index: 24.47±1.91 kg/m2, mean±standard deviation). All the participants performed two maximal incremental ramp tests on a cycle ergometer, with a prior randomized assumption of 2.5 g L-carnosine plus 2.5 g ß-alanine (Carn-ßA) or placebo (PLA). During exercise, gas exchange parameters were measured breath-by-breath, heart rate was monitored by electrocardiography and rate perceived exertion was determined on Borg scales. From the ramp test, peak cardiorespiratory and metabolic parameters and ventilatory thresholds (VT1 and VT2) were calculated offline. RESULTS: No differences between the experimental conditions emerged at peak exercise. However, despite acute Carn-ßA supplementation did not affect the single ventilatory thresholds, the compensated portion of the ramp test (i.e. the difference between VT2 and VT1) was significantly larger (P=0.043) in Carn-ßA. CONCLUSIONS: These findings demonstrate a positive effect of acute Carn-ßA supplementation on the compensated part of the exercise. This should be taken into account by nutritionists and athletes searching for nutritional supplements, when a quick effect based on an acute dose is required.

Effects of Acute Carnosine and ß-Alanine on Isometric Force and Jumping Performance.

PURPOSE: To assess the effects of acute combined L-carnosine and ß-alanine (Carn-BA) supplementation on isometric and dynamic tasks. METHODS: Twelve healthy participants performed knee-extensor maximal voluntary contractions (MVCs) and countermovement jumps (CMJs) before and after a fatiguing protocol (45-s continuous CMJs). Isometric and dynamic tests were performed 4 h after ingestion of Carn-BA (2 g of L-carnosine and 2 g of ß-alanine) or placebo (PLA), in random order. After the fatiguing protocol, blood lactate concentration ([La-]), general and muscular rating of perceived exertion (RPE), and muscle pain (24 and 48 h after the end of the fatiguing protocol) were assessed. RESULTS: During the fatiguing protocol, significant decreases in jump height and increases in contact time were found in both groups from the 15th second onward to the end of the fatiguing protocol. Average contact time and jump height were respectively lower (-7%; P = .018) and higher (+6%; P = .025) in Carn-BA than in PLA. After the fatiguing protocol, MVC decreased in both PLA and Carn-BA, but it was higher in Carn-BA than in PLA (+15%, P = 0.012), while CMJ did not change. Moreover, general RPE was lower and muscle pain at 24 h was higher in Carn-BA than in PLA, whereas muscle RPE and [La-] did not differ between conditions. CONCLUSIONS: Ingesting Carn-BA before exercise induced positive effects on MVC and CMJ after the fatiguing protocol and improved CMJ performance during the 45-s continuous jumping effort, even when acutely supplemented. Furthermore, Carn-BA reduced the general RPE and increased muscle pain 24 h after the fatiguing task.

Stretching and deep and superficial massage do not influence blood lactate levels after heavy-intensity cycle exercise.

The study aimed to assess the role of deep and superficial massage and passive stretching recovery on blood lactate concentration ([La(-)]) kinetics after a fatiguing exercise compared to active and passive recovery. Nine participants (age 23 ± 1 years; stature 1.76 ± 0.02 m; body mass 74 ± 4 kg) performed on five occasions an 8-min fatiguing exercise at 90% of maximum oxygen uptake, followed by five different 10-min interventions in random order: passive and active recovery, deep and superficial massage and stretching. Interventions were followed by 1 hour of recovery. Throughout each session, maximum voluntary contraction (MVC) of the knee extensor muscles, [La(-)], cardiorespiratory and metabolic variables were determined. Electromyographic signal (EMG) from the quadriceps muscles was also recorded. At the end of the fatiguing exercise, [La(-)], MVC, EMG amplitude, and metabolic and cardiorespiratory parameters were similar among conditions. During intervention administration, [La(-)] was lower and metabolic and cardiorespiratory parameters were higher in active recovery compared to the other modalities (P < 0.05). Stretching and deep and superficial massage did not alter [La(-)] kinetics compared to passive recovery. These findings indicate that the pressure exerted during massage administration and stretching manoeuvres did not play a significant role on post-exercise blood La(-) levels.

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.

Energetics of karate (kata and kumite techniques) in top-level athletes.

Breath-by-breath O(2) uptake (VO2, L min(-1)) and blood lactate concentration were measured before, during exercise, and recovery in six kata and six kumite karate Word Champions performing a simulated competition. VO2max, maximal anaerobic alactic, and lactic power were also assessed. The total energy cost (VO2TOT mL kg(-1) above resting) of each simulated competition was calculated and subdivided into aerobic, lactic, and alactic fractions. Results showed that (a) no differences between kata and kumite groups in VO2max, height of vertical jump, and Wingate test were found; (b) VO2TOT were 87.8 +/- 6.6 and 82.3 +/- 12.3 mL kg(-1) in kata male and female with a performance time of 138 +/- 4 and 158 +/- 14 s, respectively; 189.0 +/- 14.6 mL kg(-1) in kumite male and 155.8 +/- 38.4 mL kg(-1) in kumite female with a predetermined performance time of 240 +/- 0 and 180 +/- 0 s, respectively; (c) the metabolic power was significantly higher in kumite than in kata athletes (p < or = 0.05 in both gender); (d) aerobic and anaerobic alactic sources, in percentage of the total, were significantly different between gender and disciplines (p < 0.05), while the lactic source was similar; (e) HR ranged between 174 and 187 b min(-1) during simulated competition. In conclusion, kumite appears to require a much higher metabolic power than kata, being the energy source with the aerobic contribution predominant.