Periodized Resistance Training for Enhancing Skeletal Muscle Hypertrophy and Strength: A Mini-Review.

Prescribing the proper resistance training (RT) program is critical to optimize skeletal muscle hypertrophy and strength. Periodization is a strategy that entails planned manipulations of training variables to maximize fitness adaptations while minimizing the risk of overtraining. Multiple meta-analyses have shown periodized RT to be superior to non-periodized RT for enhancing muscular strength. These findings are consistent irrespective of training status or training volume. Both the linear model and the undulating model are effective for enhancing strength, although a greater benefit might be achieved through the undulating model. Despite the suggested superiority of periodized RT for strength development, some authors suggest that this might be a consequence of the study designs employed rather than the nature of periodized training. In addition, several limitations exist in the periodization literature, making it difficult to accurately assess the efficacy of periodized RT. With regard to enhancing skeletal muscle hypertrophy, both the undulating model and the linear model appear equally effective; however, this conclusion can only be generalized to untrained populations. When comparing periodized RT to non-periodized RT programs, the research is unclear on whether periodized RT is necessary to maximize skeletal muscle hypertrophy.

Path to doubling the efficiency of mid-IR erbium lasers.

It has been experimentally shown that a Cr:ZnSe optical amplifier can be successfully used for self-amplification of the cascade Er:Y2O3 laser. This is to our best knowledge the first demonstration of an optical amplifier where both signal and pump are delivered from a single laser source. Absorption and emission spectra of the Cr:ZnSe are perfectly positioned to amplify the output of the cascade Er:Y2O3 laser, when the 1.6 µm emission of the cascade laser serves as a pump, while 2.7 µm as a signal. We have also shown that this concept is valid for any bulk or fiber cascade erbium laser.

Power scaling of ultrafast laser inscribed waveguide lasers in chromium and iron doped zinc selenide.

We report demonstration of Watt level waveguide lasers fabricated using Ultrafast Laser Inscription (ULI). The waveguides were fabricated in bulk chromium and iron doped zinc selenide crystals with a chirped pulse Yb fiber laser. The depressed cladding structure in Fe:ZnSe produced output powers of 1 W with a threshold of 50 mW and a slope efficiency of 58%, while a similar structure produced 5.1 W of output in Cr:ZnSe with a laser threshold of 350 mW and a slope efficiency of 41%. These results represent the current state-of-the-art for ULI waveguides in zinc based chalcogenides.

840 mW continuous-wave Fe:ZnSe laser operating at 4140 nm.

We report the demonstration of high-power (840 mW) continuous-wave laser oscillation from Fe2+ ions in zinc selenide. The output spectrum of the Fe:ZnSe laser had a line-center near 4140 nm with a linewidth of 80 nm. The beam quality was measured to be M2≤1.2 with a maximum slope efficiency of 47%. Small shifts observed in output wavelength with increased output power were attributed to thermal effects. No thermal roll-off of slope efficiency was observed at the maximum of output power.