No abstract

Static stretching is widely applied in various disciplines. However, the acute effects of different durations of stretching are unclear. Therefore, this study was designed to investigate the acute effects of different stretching durations on muscle function and flexibility, and provide an insight into the optimal duration of static stretching. This randomized crossover trial included 24 healthy students (17 men and 7 women) who stretched their right hamstrings for durations of 20, 60, 180, and 300 seconds in a random order. The following outcomes were assessed using an isokinetic dynamometer as markers of lower-limb function and flexibility: static passive torque (SPT), dynamic passive torque (DPT), stiffness, straight leg raise (SLR), and isometric muscle force. Static passive torque was significantly decreased after all stretching durations (p < 0.05). Static passive torque was significantly lower after 60, 180, and 300 seconds of stretching compared with that after 20-second stretching, and stiffness decreased significantly after 180- and 300-second stretching (p < 0.05). In addition, DPT and stiffness were significantly lower after 300 seconds than after 20-second stretching (p < 0.05), and SLR increased significantly after all stretching durations (p < 0.05). Straight leg raise was higher after 180- and 300-second stretching than after 20-second stretching and higher after 300-second stretching than after 60-second stretching (p < 0.05). Isometric muscle force significantly decreased after all stretching durations (p < 0.05). Therefore, increased duration of stretching is associated with a decrease in SPT but an increase in SLR. Over 180 seconds of stretching was required to decrease DPT and stiffness, but isometric muscle force decreased regardless of the stretching duration. In conclusion, these results indicate that longer durations of stretching are needed to provide better flexibility.

Kataura, S, Suzuki, S, Matsuo, S, Hatano, G, Iwata, M, Yokoi, K, Tsuchida, W, Banno, Y, and Asai, Y. Acute effects of the different intensity of static stretching on flexibility and isometric muscle force. J Strength Cond Res 31(12): 3403-3410, 2017-In various fields, static stretching is commonly performed to improve flexibility, whereas the acute effects of different stretch intensities are unclear. Therefore, we investigated the acute effects of different stretch intensities on flexibility and muscle force. Eighteen healthy participants (9 men and 9 women) performed 180-second static stretches of the right hamstrings at 80, 100, and 120% of maximum tolerable intensity without stretching pain, in random order. The following outcomes were assessed as markers of lower limb function and flexibility: static passive torque (SPT), range of motion (ROM), passive joint (muscle-tendon) stiffness, passive torque (PT) at onset of pain, and isometric muscle force. Static passive torque was significantly decreased after all stretching intensities (p ≤ 0.05). Compared with before stretching at 100 and 120% intensities, ROM and PT were significantly increased after stretching (p ≤ 0.05), and passive stiffness (p = 0.05) and isometric muscle force (p ≤ 0.05) were significantly decreased. In addition, ROM was significantly greater after stretching at 100 and 120% than at 80%, and passive stiffness was significantly lower after 120% than after 80% (p ≤ 0.05). However, all measurements except SPT were unchanged after 80% intensity. There was a weak positive correlation between the intensities of stretching and the relative change for SPT (p ≤ 0.05), a moderate positive correlation with ROM (p ≤ 0.05), and a moderate positive correlation with passive stiffness (p ≤ 0.05). These results indicate that static stretching at greater intensity is more effective for increasing ROM and decreasing passive muscle-tendon stiffness.

The results indicate that PFMT is effective for treating SUI. There is no apparent add-on effect of BF training in short-term follow-up.

Concentrations of heavy metals in water and sediment samples of Buriganga River in the capital city Dhaka, Bangladesh, were studied to understand the level of heavy metals and their source apportionment. The results showed that the mean concentrations of heavy metals both in water and sediment samples were very high and, in most cases, exceeded the permissible limits recommended by the Bangladesh government and other international organizations. Significantly higher concentrations of Pb, Cr, Mn, Co, Ni, Cu, Zn, As, and Cd were found in sediment samples. However, average concentrations of metals both in water and sediment samples were above the effect range median. The heavy metal pollution index (HPI) and degree of contamination (Cd) yielded different results in water samples despite significant correlations between them. The heavy metal evaluation index (HEI) showed strong correlations with HPI and Cd and provided better assessment of pollution levels. The enrichment factor (EF) and geoaccumulation index (Igeo) showed the elevated value of Cr, Pb, and Cd in access of background values. The measured elements were subjected to positive matrix factorization (PMF) and examining correlations in order to explain the content, behavior, and source apportionment of metals. PMF resulted in a successful partitioning of variances into sources related to background geochemistry and contaminant influences. However, the PMF approach successfully demarcated the major sources of metals from tannery, paint, municipal sewage, textiles, and agricultural activities.