Paulo Sergio Chagas Gomes

The Effects of Stretching on Strength Performance

Strength and flexibility are common components of exercise programmes; however, it is not clear how best to include both of these elements in a single training programme. It is common practice among athletes, coaches and recreational exercisers to perform a stretching routine before a strength training session. Stretching exercises are regularly recommended, even in many textbooks, with the claimed purpose of preventing injury and muscle soreness, or even enhancing performance. However, as highlighted in recent review articles, this recommendation lacks scientific evidence. Thus, the purpose of the present review is to determine the acute and chronic effects of stretching on strength performance, together with the underlying mechanisms. Although most studies have found acute decreases in strength following stretching, and that such decreases seem to be more prominent the longer the stretching protocol, the number of exercises and sets, and the duration of each set have, in general, exceeded the ranges normally recommended in the literature. Consequently, the duration of the stimuli were excessively long compared with common practice, thus making evident the need for further studies. In addition, when recommending flexibility exercises, one should consider other underlying issues, such as the safety of the participants, possible increases in injury risks and the unnecessary time expenditure. Many mechanisms underlying stretching exercises still demand investigation so that links between the observed effects, their causes and the consequences may be constructed.

L-Arginine as a Potential Ergogenic Aidin Healthy Subjects

Dietary supplements containing L-arginine, a semi-essential amino acid, are one of the latest ergogenic aids intended to enhance strength, power and muscle recovery associated with both aerobic and resistance exercise. L-arginine is claimed to promote vasodilation by increasing nitric oxide (NO) production in the active muscle during exercise, improving strength, power and muscular recovery through increased substrate utilization and metabolite removal, such as lactate and ammonia. Research on L-arginine has recently tested this hypothesis, under the assumption that it may be the active compound associated with the vasodilator effects of NO. There were only five acute studies retrieved from the literature that evaluated exercise performance after L-arginine supplementation, three of which reported significant improvements. Regarding studies on chronic effects, eight studies were encountered: four reported enhancements in exercise performance, whilst four reports showed no changes. Whether these improvements in exercise performance — regardless of the aerobic or anaerobic nature of the exercise — can be associated with increases in NO production, has yet to be demonstrated in future studies. Low oral doses (20 g) are well tolerated and clinical side effects are rare in healthy subjects. In summary, it is still premature to recommend dietary supplements containing L-arginine as an ergogenic aid for healthy physically active subjects.

A brief review of the use of near infrared spectroscopy with particular interest in resistance exercise.

There is growing interest in resistance training, but many aspects related to this type of exercise are still not fully understood. Performance varies substantially depending on how resistance training variables are manipulated. Fatigue is a complex phenomenon usually attributed to central (neuronal) and/or peripheral (muscular) origin. Cerebral oxygenation may be associated with the decision to stop exercise, and muscle oxygenation may be related to resistance training responses. Near infrared spectroscopy (NIRS) is a non-invasive optical technique used to monitor cerebral and muscle oxygenation levels. The purpose of this review is to briefly describe the NIRS technique, validation and reliability, and its application in resistance exercise. NIRS-measured oxygenation in cerebral tissue has been validated against magnetic resonance imaging during motor tasks. In muscle tissue, NIRS-measured oxygenation was shown to be highly related to venous oxygen saturation and muscle oxidative rate was closely related to phosphocreatine resynthesis, measured by 31P-magnetic resonance spectroscopy after exercise. The test-retest reliability of cerebral and muscle NIRS measurements have been established under a variety of experimental conditions, including static and dynamic exercise. Although NIRS has been used extensively to evaluate muscle oxygenation levels during aerobic exercise, only four studies have used this technique to examine these changes during typical resistance training exercises. Muscle oxygenation was influenced by different resistance exercise protocols depending on the load or duration of exercise, the number of sets and the muscle being monitored. NIRS is a promising, non-invasive technique that can be used to evaluate cerebral and muscle oxygenation levels simultaneously during exercise, thereby improving our understanding of the mechanisms influencing performance and fatigue.

Transfer effects of endurance training with the arms and legs

The purpose of this study was to examine whether endurance training in the form of arm or leg cycling resulted in significant transfer effects when exercise was performed with the untrained muscle group. Sixteen middle-aged male volunteers completed 24 training sessions over 8 wk on either an arm cycle ergometer (AG, N = 8, mean age = 35.2 +/- 6.6 yr) or a leg cycle ergometer (LG, N = 8, mean age = 41.0 +/- 4.7 yr). The two groups were initially equated for their pre-training peak oxygen uptake (pVO2) determined during leg cycling (44.5 +/- 5.0 and 43.8 +/- 7.7 ml.kg-1.min-1 for the AG and LG, respectively). Training was performed at an intensity that was mid-way between the pre-training ventilatory threshold (VT) and the pVO2 for both cycling methods. Significant increases (P less than .05) were observed in the relative values of the oxygen uptake at the VT and the pVO2 as a result of both these methods of training, but these elevations were specific to the muscle groups that were trained. This specificity of training was also evident in the cardiorespiratory and metabolic measurements obtained during submaximal steady state exercise performed at the power output corresponding to the pre-training VT during arm and leg exercise. Hence, it was concluded that improvements in exercise performance resulting from short-term aerobic training with the arms or legs in middle-aged males with relatively high aerobic powers are due primarily to peripheral adaptations in the trained muscles.

The effects of rest intervals on jumping performance: a meta-analysis on post-activation potentiation studies.

Abstract The purpose of this meta-analytic review was to examine the extent and quality of research on the post-activation potentiation acute effect of rest interval manipulation on jumping performance. This manuscript adopted the recommendations from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement. Criteria eligibility included crossover, randomised, non-randomised and counterbalanced studies that observed the voluntary muscle action-induced post-activation potentiation on jumping performance. Fourteen studies selected by two independent raters were included in the analysis. The rest intervals involved ranges including 0–3, 4–7, 8–12 and ≥16 min. The results demonstrated medium effect sizes for rest intervals 0–3 and 8–12 min (-0.25, Confidence Interval (CI): -0.51 to 0.01 for 0–3 min; 0.24, CI: -0.02 to 0.49 for 8–12 min) and a small effect for other ranges (0.15, CI: -0.08 to 0.38 for 4–7 min; 0.07, CI: -0.21 to 0.24 for ≥16 min). There was no evidence of heterogeneity for sub-groups (I 2 = 0%; P < 0.001) and no indication of publication bias (Egger’s test, P = 0.179). While a rest interval of 0–3 min induced a detrimental effect on jump performance, the range including 8–12 min had a beneficial impact on jump height. Findings suggest that the rest interval manipulation seems to affect post-activation potentiation magnitude and jump height.

Cerebral and muscle oxygenation changes during static and dynamic knee extensions to voluntary fatigue in healthy men and women: a near infrared spectroscopy study.

The aim of the study was to examine the changes in cerebral and muscle blood volume (Cbv, Mbv) and oxygenation (Cox, Mox) during static and dynamic knee extensions to fatigue in men (N = 10; 29 ± 9 years) and women (N = 14; 27 ± 8 years). After assessment of 1 repetition maximum (1RM) during unilateral knee extensions with the dominant limb, each subject exercised at 50%, 75% and 100% of 1 RM in random order on separate occasions. Simultaneous changes in Cbv, Cox, Mbv and Mox from the contralateral prefrontal lobe and the dominant limb were measured by near infrared spectroscopy. During all three contractions, Cbv and Cox increased while Mbv and Mox decreased until fatigue in both genders. There were no signs of levelling off or decline in Cbv and Cox during any of these contractions, implying that there was no reduction in cerebral neuronal activation. Conversely, there was a rapid decline in Mbv and Mox during the early stages of the contractions, with a plateau or slight increase towards the end. The respective delta values at 50%, 75% and 100% of 1RM for Cbv (0·088 versus 0·062 versus 0·070), Cox (0·042 versus 0·033 versus 0·038), Mbv (−0·225 versus −0·198 versus −0·196), and Mox (−0·169 versus −0·146 versus −0·158) were not significantly different in the total group (N = 24). These findings suggest that fatigue during resistance exercise lasting up to 60 s is mediated peripherally because of reduced blood volume and oxygen availability and is independent of the type and intensity of muscle contraction and gender.

Does whole-body vibration acutely improve power performance via increased short latency stretch reflex response?

OBJECTIVES It remains unclear whether an increased intrafusal mechanical sensitivity is related to the vibration-induced performance improvement. This investigation aimed to determine the residual acute effect of whole-body vibration and its duration on pre-activation levels, short-latency stretch reflex and performance during drop jumps. DESIGN Repeated measures. METHODS Eleven amateur athletes performed a set of three 45cm-drop jumps before and during a 20min-interval following three randomized conditions: No, Low (30Hz, 5mm) and High vibration (45Hz, 5mm). Ground reaction force peak, Soleus and Vastus Lateralis short latency stretch reflex onset and amplitude were assessed during drop jumps. RESULTS A significant effect for time revealed an immediate drop jump height increase after High vibration. A longer contact time also followed High vibration while no changes were detected after Low vibration. Vibration did not affect ground reaction force peak and short latency stretch reflex component. CONCLUSIONS High vibration constituted an intervention for improving performance although there was no evidence of increased stretch reflex responses.

Acute effects of sustained isometric knee extension on cerebral and muscle oxygenation responses

Cerebral contra‐lateral frontal lobe and the dominant vastus lateralis muscle oxygenation (Cox, Mox) and blood volume (Cbv, Mbv) were recorded simultaneously using near infrared spectroscopy (NIRS) in 12 healthy volunteers (37·4 ± 9·9 years; 72·3 ± 16·1 kg; 171·0 ± 9·6 cm) during 2 min resting baseline, an isometric knee extension with the 1 RM load sustained to the point of fatigue, and 3 min recovery. The mean exercise duration was 19·1 ± 2·6 s. During the contraction, Cox and Cbv increased systematically with no sign of levelling off until the point of fatigue. In contrast, Mox and Mbv declined continuously until the termination of exercise. Qualitative analysis of these NIRS profiles suggested that maximal isometric performance under normoxic conditions was most likely not limited by central neuronal activation, but rather, was due to factors within the exercising muscle. It is likely that depletion of intramuscular stores of high energy phosphates and oxymyoglobin, as well as the accumulation of metabolites from anaerobic pathways, were implicated in fatigue during this sustained high intensity isometric contraction.

Confiabilidade da medida de espessuras musculares pela ultrassonografia

PURPOSE: To determine the reliability of muscle thickness measurements of elbow and knee flexors and extensors using ultrasound, and to quantify the typical error associated to the measurements (TEM). METHODS: The test-retest reliability was determined in 15 apparently healthy volunteers (8 women, 34 ± 11 years, 76 ± 21 kg, 170 ± 10 cm). The images of elbow flexors (EF) and extensors (EE) and knee flexors (KF) and extensors (KE) were obtained using a two dimensional mode B ultrasound instrument with a 7.5 MHz transducer. Muscle thickness between the adipose tissue and bone interfaces were measured at anatomical landmarks previously identified and recorded to assure the exact site for the retest. RESULTS: ANOVA did not identify any significant differences between the repeated measurements. Intraclass correlation coefficients (ICC) of each pair of measure were EF = 0.970, EE = 0.971, KF = 0.555 e KE = 0.929 (P < 0.05 for all). The coefficients of variation were 3.9 %, 6.1 %, 6.6 % e 4.6 %, and TEM 1.3 mm, 1.6 mm, 4.9 mm e 1.9 mm, respectively, for the EF, EE, KF and KE thickness. Analysis of the Bland-Altman plot charts indicated that the variables did not present heterocedastic errors. CONCLUSION: EF, EE and KE muscle thickness measurements using the current method were highly reliable and can be used to measure and monitor changes in diet, physical training and rehabilitation programs. Nevertheless, KF measure should not be recommended since it presented low reliability and high TEM.

Gasto energético e consumo de oxigênio pós-exercício contra-resistência

The increase in energy expenditure through physical activity is recognized as an important component in weight loss programs. The impact of resistance exercise, including excess post-exercise oxygen consumption (correspond to the post-exercise energy expenditure), on energy expenditure, however, remains inconclusive. The purpose of the present review was to discuss the influence of the resistance exercise variables (intensity, rest interval, movement velocity, number of sets, and type - circuit or continuous) on energy expenditure during and after an exercise bout. The excess post-exercise oxygen consumption mechanisms were also discussed. The innumerous possibilities of combinations among resistance exercise variables result in a wide range of energy expenditure values for an exercise session (approximately between 3 to 10kcal·min-1). Nevertheless, volume appears to be determinant in the energy expenditure of resistance exercise itself, excess post-exercise oxygen consumption, on the other side, may be affected by exercise intensity. The manipulation of resistance exercise variables may affect the metabolic processes underlying excess post-exercise oxygen consumption, including resynthesis of high energy phosphates stores, resaturation of oxyhemoglobin and oxymyoglobin, thermogenic effects, lactate removal, increased protein turnover, and effects mediated by sympathetic activity. In conclusion, it might be advisable to use low intensity and high volume exercises in a training session for untrained and overweight subjects. However, trained individuals could benefit from more intense resistance exercise, due to the effects of intensity on excess post-exercise oxygen consumption. Thus, nutritionists should consider the effects of resistance exercise on total energy expenditure in order to prescribe effective diets for weight loss purposes.