Effect of Reduced Stiffness Dance Flooring on Lower Extremity Joint Angular Trajectories During a Ballet Jump.

We carried out a study to investigate how low stiffness flooring may help prevent overuse injuries of the lower extremity in dancers. It was hypothesized that performing a ballet jump (sauté) on a reduced stiffness dance floor would decrease maximum joint flexion angles and negative angular velocities at the hips, knees, or ankles compared to performing the same jump on a harder floor. The participants were 15 young adult female dancers (age range 18 to 28, mean = 20.89 ± 2.93 years) with at least 5 years of continuous ballet experience and without history of serious lower body injury, surgery, or recent pain. They performed sautés on a (low stiffness) Harlequin ® WoodSpring Floor and on a vinyl-covered hardwood on concrete floor. Maximum joint flexion angles and negative velocities at bilateral hips, knees, and ankles were measured with the "Ariel Performance Analysis System" (APAS). Paired one-tailed t-tests yielded significant decreases in maximum knee angle (average decrease = 3.4° ± 4.2°, p = 0.026) and angular negative velocity of the ankles (average decrease = 18.7°/sec ± 27.9°/sec, p = 0.009) with low stiffness flooring. If the knee angle is less acute, then the length of the external knee flexion moment arm will also be shorter and result in a smaller external knee flexion moment, given an equal landing force. Also, high velocities of eccentric muscle contraction, which are necessary to control negative angular velocity of the ankle joint, are associated with higher risk of musculotendinous injury. Hence, our findings indicate that reduced floor stiffness may indeed help decrease the likelihood of lower extremity injuries.

The effect of sprung (suspended) floors on leg stiffness during grand jeté landings in ballet.

This study compared stiffness of the landing leg in ballet dancers performing grand jeté on a sprung floor to leg stiffness during the same movement on a hard floor (wood on concrete). Leg stiffness was calculated as the ratio of vertical ground reaction force (in Newtons) to compression of the lower limb (in meters). Thirteen female dancers were measured for five repetitions each at the point of maximum leg compression while landing grand jeté on both of the surfaces, such that 20 milliseconds of data were represented for each trial. The stiffness of the landing leg at the point of maximum compression was decreased by a mean difference score of 6168.0 N/m ± 11,519.5 N/m on the hard floor compared to the sprung floor. Paired t-test yielded a one-tailed probability of p = 0.038. This effect was seen in 11 of the 13 participants. The finding of increased stiffness of the landing leg in the sprung floor condition suggests that some of the force of landing the leap was absorbed by the surface, and therefore did not need to be absorbed by the landing leg itself. This in turn implies that a sprung dance floor may help to prevent dance-related injuries.

Effect of sprung (suspended) floor on lower extremity stiffness during a force-returning ballet jump.

Our objective in this study was to compare stiffness of bilateral lower extremities (LEs) in ballet dancers performing sauté on a low-stiffness "sprung floor" to that during the same movement on a high-stiffness floor (wood on concrete). LE stiffness was calculated as the ratio of vertical ground reaction force (in kN) to compression of the lower limb (in meters). Seven female dancers were measured for five repetitions each at the point of maximum leg compression while performing sauté on both of the surfaces, such that 43 ms of data were represented for each trial. The stiffness of bilateral LEs at the point of maximum compression was higher by a mean difference score of 2.48 ± 2.20 kN/m on the low-stiffness floor compared to a high-stiffness floor. Paired t-test analysis of the difference scores yielded a one-tailed probability of 0.012. This effect was seen in six out of seven participants (one participant showed no difference between floor conditions). The finding of increased stiffness of the LEs in the sprung floor condition suggests that some of the force of landing the jump was absorbed by the surface, and therefore did not need to be absorbed by the participants' LEs themselves. This in turn implies that a sprung dance floor may help to prevent dance-related injuries.

Cyclopropane-containing polyamine analogues are efficient growth inhibitors of a human prostate tumor xenograft in nude mice.

Polyamine analogues 7, 10, 18, 27, and 32 containing cyclopropane rings were obtained by chemical synthesis. Their antineoplastic activities were assessed against the cultured human prostate tumor cell lines DU-145, DuPro, and PC-3. Decamines 32 and 27 exhibited variable levels of cytotoxicity against all three cell lines, while 7, 10, and 18 were efficacious against DU-145 and DuPro. Maximum tolerated doses (MTD) for all five compounds in a NCr-nu mouse model were determined at dosing schedules of q1d x 5 (ip) in two cycles with a break of 10 days between cycles. Their antitumor efficacies were then tested against DU-145 tumor xenografts in mice treated with all five agents at their respective MTDs. In addition, the efficacies of 7 and 10 against the same tumor xenograft were assessed at doses below their respective MTDs. In all experiments, administration began two weeks after tumor implantation. All compounds efficiently inhibited tumor growth for up to 50 days postimplantation, with negligible animal body weight loss. Tetramine 10 and hexamine 18 were the most efficient among the five analogues in arresting tumor growth. Tetramine 10 containing two cyclopropane rings had the lowest systemic toxicity as reflected in animal body weight loss. It was further assessed at a weekly administration regimen of (q1w x 4) in two cycles with a four-week break between the cycles. At this dosing schedule, 10 again efficiently arrested tumor growth with negligible effect on animal body weight. Tetramine 10 also arrested the growth of large tumors (ca. 2000 mm(3)) treated 66 days postimplantation. Studies on the metabolism of 10 showed that it accumulates in tumor within 6 h after the end of administration and reached a maximum level 72 h after cessation of dosing. Intracellular concentrations of 10 in liver and kidney were much smaller when compared to those in the tumor when measured 72 h after cessation of dosing. In liver and kidney, the deethyl metabolites of 10 accumulated over a 96 h period after cessation of dosing.