Effect of water depth on muscle activity and stride duration when walking in the water at different speeds.

Aquatic exercise is popular for training and rehabilitation, but information on how the water depth affects muscle activity when walking is lacking. The purpose of this study was to compare muscle activity when walking on land and at knee, pelvis and xiphoid process depth in a swimming pool. Twelve participants (22 ± 3.6 years; 70.9 ± 14.5 kg; 1.7 ± 0.1 m) walked on land and on the pool floor at each of the three depths, at a self-selected (Vself) and a maximum speed (Vmax). Mean and peak muscle activity was recorded for the rectus femoris (RF), biceps femoris (BF), medial gastrocnemius (GM), lateral gastrocnemius (GL), tibialis anterior (TA) and erector spinae (ES). Stride duration was also recorded. Stride duration decreased and activity of all muscles increased from Vself to Vmax, except peak values at xiphoid process depth. For the depth comparisons, most changes in muscle activity occurred in the RF and BF, with higher values generally occurring at knee and pelvis depth, and stride duration continually increased with depth. These findings provide useful information on the musculoskeletal demands of walking in the water that can be used to inform design and prescription of exercise programmes for rehabilitation.

Cellulase-lignin interactions-the role of carbohydrate-binding module and pH in non-productive binding.

Non-productive cellulase adsorption onto lignin is a major inhibitory mechanism preventing enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding of enzyme-lignin interactions is essential for the development of enzyme mixtures and processes for lignocellulose hydrolysis. We have studied cellulase-lignin interactions using model enzymes, Melanocarpus albomyces Cel45A endoglucanase (MaCel45A) and its fusions with native and mutated carbohydrate-binding modules (CBMs) from Trichoderma reesei Cel7A. Binding of MaCel45A to lignin was dependent on pH in the presence and absence of the CBM; at high pH, less enzyme bound to isolated lignins. Potentiometric titration of the lignin preparations showed that negatively charged groups were present in the lignin samples and that negative charge in the samples was increased with increasing pH. The results suggest that electrostatic interactions contributed to non-productive enzyme adsorption: Reduced enzyme binding at high pH was presumably due to repulsive electrostatic interactions between the enzymes and lignin. The CBM increased binding of MaCel45A to the isolated lignins only at high pH. Hydrophobic interactions are probably involved in CBM binding to lignin, because the same aromatic amino acids that are essential in CBM-cellulose interaction were also shown to contribute to lignin-binding.