The mechanical loading and muscle activation of four common exercises used in osteoporosis prevention for early postmenopausal women.

High impact exercise can reduce postmenopausal bone loss, however stimulus frequency (loading cycles per second) can affect osteogenesis. We aimed to examine the effect of stimulus frequency on the mechanical loading of four common osteoporosis prevention exercises, measuring body acceleration and muscle activation with accelerometry and electromyography (EMG), respectively. Fourteen early postmenopausal women completed randomised countermovement jumps (CMJ), box-drops (BD), heel-drops (HD) and stamp (STP) exercises for continuous and intermittent stimulus frequencies. Sacrum accelerometry and surface electromyography (EMG) of four muscles were recorded. CMJ (mean ±â€¯SD: 10.7 ±â€¯4.8 g & 10.0 ±â€¯5.0 g), BD (9.6 ±â€¯4.1 g & 9.5 ±â€¯4.0 g) and HD (7.3 ±â€¯3.8 g & 8.6 ±â€¯4.4 g) conditions generated greater peak acceleration than STP (3.5 ±â€¯1.4 g & 3.6 ±â€¯1.7 g) across continuous and intermittent trials. CMJ and BD generated greater acceleration gradients than STP across continuous and intermittent trials. CMJ generated greater rectus femoris EMG than all other exercises, CMJ and BD generated greater semitendinosus and tibialis anterior EMG than HD across continuous and intermittent trials. CMJ and BD provide greater peak acceleration than STP and remain similar during different stimulus frequencies. CMJ, BD and HD may exceed STP in maintaining postmenopausal bone health.

Tibial impacts and muscle activation during walking, jogging and running when performed overground, and on motorised and non-motorised treadmills.

PURPOSE: To examine tibial acceleration and muscle activation during overground (OG), motorised treadmill (MT) and non-motorised treadmill conditions (NMT) when walking, jogging and running at matched velocities. METHODS: An accelerometer recorded acceleration at the mid-tibia and surface EMG electrodes recorded rectus femoris (RF), semitendinosus (ST), tibialis anterior (TA) and soleus (SL) muscle activation during OG, MT and NMT locomotion whilst walking, jogging and running. RESULTS: The NMT produced large reductions in tibial acceleration when compared with OG and MT conditions across walking, jogging and running conditions. RF EMG was small-moderately higher in the NMT condition when compared with the OG and MT conditions across walking, jogging and running conditions. ST EMG showed large and very large increases in the NMT when compared to OG and MT conditions during walking whilst SL EMG found large increases on the NMT when compared to OG and MT conditions during running. The NMT condition generated very large increases in step frequency when compared to OG and MT conditions during walking, with large and very large decreases during jogging and very large decreases during running. CONCLUSIONS: The NMT generates large reductions in tibial acceleration, moderate to very large increases in muscular activation and large to very large decreases in cycle time when compared to OG and MT locomotion. Whilst this may decrease the osteogenic potential of NMT locomotion, there may be uses for NMTs during rehabilitation for lower limb injuries.

Individualisation of time-motion analysis: a method comparison and case report series.

This study compared the intensity distribution of time-motion analysis data, when speed zones were categorized by different methods. 12 U18 players undertook a routine battery of laboratory- and field-based assessments to determine their running speed corresponding to the respiratory compensation threshold (RCT), maximal aerobic speed (MAS), maximal oxygen consumption (vV˙O2max) and maximal sprint speed (MSS). Players match-demands were tracked using 5 Hz GPS units in 22 fixtures (50 eligible match observations). The percentage of total distance covered running at high-speed (%HSR), very-high speed (%VHSR) and sprinting were determined using the following speed thresholds: (1) arbitrary; (2) individualised (IND) using RCT, vV˙O2max and MSS; (3) individualised via MAS per se; (4) individualised via MSS per se; and (5) individualised using MAS and MSS as measures of locomotor capacities (LOCO). Using MSS in isolation resulted in 61% and 39% of player's % HSR and % VHSR, respectively, being incorrectly interpreted, when compared to the IND technique. Estimating the RCT from fractional values of MAS resulted in erroneous interpretations of % HSR in 50% of cases. The present results suggest that practitioners and researchers should avoid using singular fitness characteristics to individualise the intensity distribution of time-motion analysis data. A combination of players' anaerobic threshold, MAS, and MSS characteristics are recommended to individualise player-tracking data.

Side-effects of intradermal injections of botulinum A toxin in the treatment of palmar hyperhidrosis: a neurophysiological study.

Focal palmar hyperhidrosis can be effectively abolished by intradermal injections with botulinum toxin. Muscle weakness of finger grip has been reported as a reversible side-effect of this new treatment. The objective of this work was to measure muscular side-effects after treatment of palmar hyperhidrosis with botulinum toxin. As botulinum toxin has been used in the treatment of pain, we studied whether the toxin might influence afferent thin-fibre function by measuring temperature perception thresholds. Thirty-seven patients treated with botulinum toxin (Botox, Allergan Pharmaceuticals, Irvine, CA, USA) showed a decrease in compound muscle action potential (CMAP) for both abductor pollicis brevis (APB) and abductor digiti minimi (ADM) compared with pre-injection values on average by 64 and 36%, respectively, at 3 weeks which returned nearly to normal at 37 weeks. Muscle power for both finger abduction and finger opposition decreased to a lesser extent. Repetitive nerve stimulation and single fibre electromyography (EMG) showed a disturbed neuromuscular transmission. Thus, despite careful technique with small doses of botulinum toxin injected intradermally, the toxin diffuses to underlying muscles. With regard to the present results, one should be careful in using higher doses of Botox than 0.8 mU/cm(2) in the palmar skin above intrinsic muscles. No influence on thin-fibre function was seen.

Kinanthropometric and physiological characteristics of outrigger canoe paddlers.

We describe the physiological characteristics of amateur outrigger canoe paddlers. Twenty-one paddlers (13 males, 8 females) were evaluated for body stature, aerobic power, muscular strength and endurance, peak paddle force, flexibility and 250 m sprint paddle performance at the end of the outrigging season. The mean variables (+/- s) for the males were: age 27 +/- 9 years, height 175 +/- 5 cm, body mass 80 +/- 5 kg, arm span 178 +/- 7 cm, sitting height 100 +/- 2 cm, aerobic power 3.0 +/- 0.4 l x min(-1), maximum bench press strength 85 +/- 19 kg, right peak paddle force 382 +/- 66 N and left peak paddle force 369 +/- 69 N. For the females, these were: age 26 +/- 6 years, height 168 +/- 5 cm, body mass 70 +/- 8 kg, arm span 170 +/- 5 cm, sitting height 97 +/- 3 cm, aerobic power 2.3 +/- 0.51 l x min(-1), maximum bench press strength 47 +/- 10 kg, right peak paddle force 252 +/- 63 N and left peak paddle force 257 +/- 60 N. Analysis of variance revealed differences (P < 0.05) between the dominant and non-dominant sides of the body for peak paddle force, isokinetic internal and external rotation, and flexion and extension torque of the shoulder joint. The outrigger canoe paddlers were generally within the range of scores found to describe participants of other water craft sports. Outrigger canoeists should be concerned with the muscular strength imbalances associated with paddling technique.

The effect of a high-carbohydrate diet on the skill performance of midfield soccer players after intermittent treadmill exercise.

This study examined the effect of a high-carbohydrate diet on the performance of dribbling and shooting skills of recreational soccer players. Six male midfield soccer players first completed 60 minutes of intermittent treadmill exercise, followed either by a mixed or a high-carbohydrate diet for 48 hours. A modified Zelenka Functional Performance Test was then administered, followed by the intermittent treadmill exercise and another skills test. Subjects then repeated the protocol two weeks later under the alternative dietary regime. Blood samples were obtained pre exercise and after each procedure for Hematocrit and concentrations of hemoglobin, plasma glucose and lactate. Heart rate was recorded during and after each procedure. Repeated measures MANOVA revealed (1) the skill performance was not impaired by the intermittent treadmill exercise (p > 0.05); (2) the high-carbohydrate diet did not increase the ability of players to shoot or dribble (p > 0.05); (3) a significant increase in heart rate during the post treadmill exercise skill test compared with that during the pre treadmill exercise test (p < 0.05); (4) a significant order by time effect for hematocrit (p < 0.05); (5) no significant differences in plasma glucose, plasma lactate or hemoglobin concentrations between tests (p > 0.05); and (6) a significant decrease in body mass from pre to post dietary regime within both conditions (p < 0.05). It is speculated that either (1) muscle glycogen depletion may not impair the ability of the player to execute game skills; (2) an alternative fatigue mechanism such as dehydration or increased lactate production may be causative factors in the reduction in skill performance; or (3) the treadmill protocol employed failed to induce a degree of glycogen depletion or fatigue large enough to cause a significant fall in skill performance.

The role of N-acetylcysteine as a putative radioprotective agent on X-ray-induced DNA damage as evaluated by alkaline single-cell gel electrophoresis.

Samples of human whole blood from 8 different donors were incubated with physiological saline or N-acetyl-L-cysteine (NAC, 1 x 10(-3) M) before being irradiated in vitro with high-energy X-rays (0.7 or 2.0 Gy). Primary DNA damage was evaluated in isolated lymphocytes using alkaline single-cell gel electrophoresis. Whereas the lymphocytes from non-irradiated blood samples showed a similar 'background level' of damage, there was a difference in sensitivity towards the radiation-induced DNA damage, especially at 2.0 Gy. When the data were pooled there was a clear and dose-related increase (p < 0.001) in damage, both in the absence and presence of NAC. Using the two most sensitive 'comet parameters' for DNA damage, i.e., the tail inertia and tail moment, the radiation-induced damage was found to be significantly increased already at 0.7 Gy in the samples that had been irradiated without NAC. Overall, NAC was found to be without radioprotective effects. Instead, the incubation with NAC itself was found to be associated with a slightly increased level of DNA damage. If the present findings are relevant also in an in vivo situation using peripheral lymphocytes as a surrogate for non-malignant cells in the body, NAC seems to be of limited value as a radioprotective agent in the clinic, at least when it comes to the acute DNA-damaging effects of therapeutic doses of high-energy X-rays.