Effect of movement speed on trunk and hip exercise performance.

The influence of speed on trunk exercise technique is poorly understood. The aim of this study was to analyse the effect of movement speed on the kinematics and kinetics of curl-up, sit-up and leg raising/lowering exercises. Seventeen healthy, recreationally trained individuals (13 females and 4 males) volunteered to participate in this study. Four different exercise cadences were analysed: 1 repetition/4 s, 1 repetition/2 s, 1 repetition/1.5 s and 1 repetition/1 s. The exercises were executed on a force plate and recorded by three cameras to conduct a 3D photogrammetric analysis. The cephalo-caudal displacement of the centre of pressure and range of motion (ROM) of six joints describing the trunk and hip movements were measured. As sit-up and curl-up speed increased, hip and knee ROM increased. Dorsal-lumbar and upper trunk ROM increased with speed in the curl-up. Faster cadence in the sit-up exercise had minimal effect on trunk ROM: only the upper trunk ROM decreased significantly. In the leg raising/lowering exercise there was a decrease in the pelvic tilt and hip ROM, and increased knee flexion ROM. During higher speed exercises, participants modified their technique to maintain the cadence. Thus, professionals would do well to monitor and control participants' technique during high-speed exercises to maintain performance specificity. Results also suggest division of speed into two cadence categories, to be used as a reference for prescribing exercise speed based on preferred outcome goals.

On-line solid phase extraction of Ni and Pb using carbon nanotubes and modified carbon nanotubes coupled to ETAAS.

A study about the capabilities of three kinds of nanomaterials namely, carbon nanotubes (CNT), oxidized carbon nanotubes (ox-CNT) and l-alanine immobilized on carbon nanotubes (ala-CNT) to serve as sorbents for preconcentrating Ni and Pb using an on-line system coupled to electrothermal atomic absorption spectroscopy (ETAAS) technique, was accomplished. The solid phase extraction was performed in a conical minicolumn used as sorbent holder. After loading a fixed volume of the analytes, they were eluted with a discrete volume (50 µL) of nitric acid, placed directly into the platform of a L'Vov tube. After that, each analyte was determined individually. Ni and Pb retention was strongly influenced by pH but exhibiting different behaviors. The study demonstrated that the sorbent based on ox-CNTs was the one that exhibited the highest capacity and linearity for both analytes when compared with CNT or ala-CNT. The analytical performance was evaluated for the three sorbents to establish the best conditions regarding sensitivity, reproducibility and accuracy. The precision expressed as relative standard deviations (n=6) were 3.9 and 0.5% for Ni(2+) and Pb(2+), respectively The limit of detection (LOD), calculated as the concentration required to yield a net peak equal to three times the standard deviation of the background signal (3σ) was 30 and 10 ng L(-1) for Ni(2+) and Pb(2+) respectively. Alternatively, the limit of quantification (10σ) was calculated and resulted to be 0.79 and 0.07 µg L(-1) for Ni(2+) and Pb(2+) respectively. After optimization, the method that involved the use of ox-CNT associated to an on-line preconcentration was tested in samples of relevant environmental importance. Accuracy was evaluated analyzing a certified reference material namely, Municipal Sludge (QC MUNICIPAL SLUDGE A) and a reference sample of Lake Sediment (TRAP-LRM from IJS).

Influence of trunk curl-up speed on muscular recruitment.

Although exercise speed is an acute variable to prescribe abdominal strengthening programs, current literature lacks studies analyzing the influence of speed on muscular activation in abdominal exercises. The aim of this work was to determine the influence of trunk curl-up speed on the amplitude of muscular activation and the way in which the trunk muscles were coactivated. Twenty recreationally trained volunteers (16 women and 4 men; age, 23.7 +/- 4.3 years; height, 166.2 +/- 6.3 cm; mass, 61.0 +/- 8.2 kg) participated in this study. Surface electromyographic data were collected from the rectus abdominis, external oblique, internal oblique, and erector spinae during 4 different curl-up cadences [1 repetition per 4 seconds (C4), 1 repetition per 2 seconds (C2), 1 repetition per 1.5 seconds (C1.5), 1 repetition per 1 second (C1)], and during maximum speed curl-ups (Cmax). The electromyographic amplitude was averaged and normalized using maximum voluntary isometric contractions (MVICs). Statistical analyses were performed using repeated-analyses of variance. Normalized electromyographic mean amplitudes of trunk muscles increased with curl-up speed. Although the rectus abdominis (ranged from 23.3% of MVICs at C4 to 49.6% of MVICs at Cmax) and internal oblique (ranged from 19.2% of MVICs at C4 to 48.5% of MVICs at Cmax) were the most active analyzed muscles at each speed, contribution of the external oblique increased appreciably with velocity (ranged from 5.3% of MVICs at C4 to 33.3% of MVICs at Cmax). Increasing trunk curl-up speed supposed greater trunk muscular coactivation, probably required for a faster performance and to ensure dynamic spine stability. On the basis of our findings, curl-up speed had an important effect on trunk muscular recruitment and must be taken into account when prescribing exercise programs for abdominal conditioning.