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 (31)P-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.

Movement velocity in resistance training.

Guidelines for resistance training include the number of exercises, sets, repetitions, and frequency of training, but only vaguely mention movement velocity. Nevertheless, different velocities imply different performances, i.e. a different number of repetitions or different loads. Studies investigating the effect of different movement velocities on resistance training have not reached a consensus. Some studies indicate specificity in strength gains while others indicate generality. Some indicate slow training to be better, others indicate fast training, and still others indicate no differences. Most of these studies were conducted on isokinetic or hydraulic equipment. Very few used isotonic equipment for training, and their results seem to tend towards generality and no differences in gains of strength between velocities. Defining the training velocity is mostly important for athletic performances where a wide range of velocities is needed and transfer of gains would greatly optimise training. At the other end of the spectrum, there are the most frail and elderly, to whom power loss may impair even daily functions, but training with fast velocities might increase injury risk and, therefore, transfer of gains from slow training would be greatly beneficial. Movement velocity for resistance training with isotonic equipment needs to be further investigated so that recommendations may be made.