Sprint performance and propulsion asymmetries on an ergometer in trained high- and low-point wheelchair rugby players.

The purpose of this study was to examine the propulsion asymmetries of wheelchair athletes while sprinting on an instrumented, dual-roller ergometer system. Eighteen experienced wheelchair rugby players (8 low point (LP) (class ≤1.5) and 10 high point (HP) (class ≥2.0)) performed a 15-second sprint in their sports wheelchair on the instrumented ergometer. Asymmetry was defined as the difference in distance and power output (PO) between left and right sides when the best side reached 28 m. Propulsion techniques were quantified based on torque and velocity data. HP players covered an average 3 m further than the LP players (P = .002) and achieved faster sprint times than LP players (6.95 ± 0.89 vs 8.03 ± 0.68 seconds, P = .005) and at the time the best player finished (5.96 seconds). Higher peak POs (667 ± 108 vs 357 ± 78 W, P = .0001) and greater peak speeds that were also evident were for HP players (4.80 ± 0.71 vs 4.09 ± 0.45 m/s, P = .011). Greater asymmetries were found in HP players for distance (1.86 ± 1.43 vs 0.70 ± 0.65 m, P = .016), absolute peak PO (P = .049), and speed (0.35 ± 0.25 vs 0.11 ± 0.10 m/s, P = .009). Although HP players had faster sprint times over 28 m (achieved by a higher PO), high standard deviations show the heterogeneity within the two groups (eg, some LP players were better than HP players). Quantification of asymmetries is important not only for classifiers but also for sports practitioners wishing to improve performance as they could be addressed through training and/or wheelchair configuration.

Hand-rim forces and gross mechanical efficiency in asynchronous and synchronous wheelchair propulsion: a comparison.

To compare the force application characteristics at various push frequencies of asynchronous (ASY) and synchronous (SYN) hand-rim propulsion, 8 able-bodied participants performed a separate sub-maximal exercise test on a wheelchair roller ergometer for each propulsion mode. Each test consisted of a series of 5, 4-min exercise blocks at 1.8 m · s-1 - initially at their freely chosen frequency (FCF), followed by four counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMARTWheel, measuring forces and moments. The gross efficiency (GE) was determined as the ratio of external work done and the total energy expended. The ASY propulsion produced higher force measures for FRES, FTAN, rate of force development & FEF (P<0.05), while there was no difference in GE values (P=0.518). In pair-matched push frequencies (ASY80:SYN60, ASY100:SYN80, ASY120:SYN100 and ASY140:SYN120), ASY propulsion forces remained significantly higher (FRES, FTAN, rate of force development & FEF P<0.05), and there was no significant effect on GE (P=0.456). Both ASY and SYN propulsion demonstrate similar trends: changes in push frequency are accompanied by changes in absolute force even without changes in the gross pattern/trend of force application, FEF or GE. Matched push frequencies continue to produce significant differences in force measures but not GE. This suggests ASY propulsion is the predominant factor in force application differences. The ASY would appear to offer a kinetic disadvantage to SYN propulsion and no physiological advantage under current testing conditions.

Effect of low-compression balls on wheelchair tennis match-play.

The purpose of this study was to compare court-movement variables and physiological responses to wheelchair tennis match-play when using low vs. standard compression tennis balls. Eleven wheelchair basketball players were monitored during repeated bouts of tennis (20 min) using both ball types. Graded and peak exercise tests were completed. For match-play, a data logger was used to record distance and speed. Individual linear heart rate oxygen consumption relationships were used to estimate match-play oxygen uptake. Significant main effects for ball type revealed that total distance (P<0.05), forward distance (P<0.05), and average speed (P<0.05) were higher for play using a low-compression ball. A lower percentage of total time was spent stationary (P<0.001), with significantly more time spent at speeds of 1-1.49 (P<0.05), 1.5-1.99 (P<0.05) and 2.0-2.49 (P<0.05) m ∙ sec(-1) when using the low-compression ball. Main effects for physiological variables were not significant. Greater total and forward distance, and higher average speeds are achieved using a low-compression ball. The absence of any difference in measured HR and estimated physiological responses would indicate that players move further and faster at no additional mean physiological cost. This type of ball will be useful for novice players in the early phases of skill development.

Hand-rim forces and gross mechanical efficiency at various frequencies of wheelchair propulsion.

To determine the effects of push frequency changes on force application, fraction of effective force (FEF) and gross efficiency (GE) during hand-rim propulsion. 8 male able-bodied participants performed five 4-min sub-maximal exercise bouts at 1.8 ms(-1); the freely chosen frequency (FCF), followed by 4 counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMART(Wheel), measuring forces and moments. The GE was determined as the ratio of external work done and the total energy expended. Increased push frequency led to reductions in peak resultant force (P<0.05), ranging from 167 to 117 N and peak tangential force (P<0.05), ranging from 117 to 77 N. However, FEF only demonstrated a significant difference between 60% and 140% FCF (69 ± 9% and 63 ± 7, respectively; P<0.05). Work per cycle decreased significantly (P<0.05) and rate of force development increased significantly (P<0.05) with increased push frequency. GE values were significantly lower at 60%, 120% and 140% FCF than 80% and 100% FCF (P<0.05). No meaningful associations were present between FEF and GE. Under the current testing conditions, changes in push frequency are accompanied with changes in the absolute force values, albeit without changes in either the gross pattern/trend of force application or FEF. Changes in GE are not explained by different levels of force effectiveness.

The effect of wheel size on mobility performance in wheelchair athletes.

The purpose of the current study was to investigate the effects of different wheel sizes, with fixed gear ratios, on maximal effort mobility performance in wheelchair athletes. 13 highly trained wheelchair basketball players, grouped by classification level, performed a battery of 3 field tests in an adjustable wheelchair with 3 different wheel sizes (0.59 m, 0.61 m and 0.65 m). Performance was assessed using the time taken to perform drills, with velocity and acceleration data also collected via a wheelchair velocometer. 20 m sprint time improved in the 0.65 m condition (5.58 ± 0.43 s, P=0.029) compared with 0.59 m (5.72 ± 0.40 s). Acceleration performance over the first 2 (P=0.299) and 3 (P=0.145) pushes was not statistically influenced by wheel size. However, the peak velocities reached were greater in the 0.65 m condition (4.77 ± 0.46 m ∙ s(-1), P=0.078, Effect Size [ES]=0.63) compared with 0.59 m (4.61 ± 0.40 m ∙ s(-1)). Impact velocity, calculated as the change in velocity from the onset of a push to the following impact peak, to define coupling performance, was also significantly improved in 0.65 m wheels (0.14 ± 0.14 m ∙ s(-1), P=0.006) than 0.59 m wheels (0.05 ± 0.10 m ∙ s(-1)). The time taken to complete the linear mobility (P=0.630) and the agility drill (P=0.505) were not affected by wheel size. Finally, no significant interactions existed between wheel size, classification and any performance measure. To conclude, larger 0.65 m wheels improved the maximal sprinting performance of highly trained wheelchair basketball players, without any negative effects on acceleration or manoeuvrability. Improvements in sprinting were attributed to a combination of the reduced drag forces experienced and improvements in coupling thought to be due to the lower angular velocities of the wheel/hand-rim when developing high wheelchair velocities in larger wheels.

Influence of varied tempo music on wheelchair mechanical efficiency following 3-week practice.

The purpose of this study was to analyse adaptations in propulsion technique and gross efficiency in novice able-bodied subjects during the initial phase of learning hand-rim wheelchair propulsion to music. 22 able bodied participants performed wheelchair propulsion (1.1 m·s(-1)) followed by a VO(2) peak test on a wheelchair ergometer. Push frequency, gross efficiency (GE), heart rate, rating of perceived exertion and propulsion technique variables (force application and temporal characteristics) were recorded. Participants were then assigned to a 3-wk practice period listening to i) 125 beats·min(-1) tempo music (LOW); ii) 170 beats·min(-1) tempo music (HIGH); or iii) a control group (CON). Following practice, all participants repeated the pre-testing protocol whilst force application data was collected in practice trials 1 and 9. After accounting for the pre-practice differences in GE (using ANCOVA), GE was higher in LOW compared with CON (P=0.038; 6.6 vs. 6.1% respectively). The differences between CON vs. HIGH and LOW vs. HIGH (P=0.830; P=0.188) were trivial suggesting that only LOW experienced an increase in GE. Practice had a favourable effect on the perceptions of effort, work per cycle, push and cycle time in contrast to the CON group. The use of music in a rehabilitation setting warrants further investigation.

Effects of arm frequency during synchronous and asynchronous wheelchair propulsion on efficiency.

To further understand the possible underlying mechanisms of the low efficiencies in hand rim wheelchair propulsion, this study examined efficiency indices at different arm frequencies during two propulsion modes (synchronous and asynchronous). Fourteen male able-bodied participants performed VO2PEAK tests for both propulsion modes. Subsequently two sub-maximal exercise tests examining synchronous and asynchronous propulsion were completed at an individualised velocity (60% of VO2PEAK). The freely chosen arm frequency (FCF), followed by four counter-balanced trials at 60, 80, 120, and 140% of FCF were performed. Gross, net, and work efficiency were determined. Gross efficiency was significantly lower (p<0.05) at arm frequencies >100%, and participants were more efficient between 60 to 100% FCF. These arm frequencies corresponded to 76+/-22 to 126+/-36 and 70+/-18 to 116+/-30 pushes x min(-1) (synchronous and asynchronous respectively). Trends in VO2, gross and work efficiency suggest that 80% of FCF produced the best economy and efficiency during both propulsion modes (non-significant). Gross and work efficiency at 80% FCF were 6.8+/-0.7% and 13.0+/-4.6% for synchronous and 7.0+/-0.8% and 11.5+/-1.6% for asynchronous respectively. The results suggest that during both modes of propulsion the FCF is not necessarily the most efficient.

Embolization of renal angiomyolipoma: immediate complications and long-term outcomes.

AIMS: To report the outcomes of elective and emergency embolization of renal angiomyolipoma and describe an angiographic sign that will help localize the symptomatic aneurysm in emergency cases. MATERIALS AND METHODS: A retrospective review of all patients undergoing embolization of renal angiomyolipoma at a two centres between 1998-2007. Indications for treatment and angiographic images were reviewed. Incidence of acute rupture during embolization was noted. RESULTS: Seventeen patients underwent 23 episodes of embolization using polyvinyl alcohol (PVA) particles, bead block, and coils. Thirteen were elective procedures for large or symptomatic angiomyolipoma and 10 were acute procedures for patients presenting with retroperitoneal haemorrhage. Patients presenting acutely with haemorrhage tended to have extensive multifocal renal involvement. Active bleeding on diagnostic angiography was seen in a single patient who presented with retroperitoneal haemorrhage 48h after elective embolization with PVA alone. Seven out of 10 (70%) of the acute cases displayed splaying of adjacent vessels due to peri-aneurysmal haematoma, known locally as the "light bulb sign". This allowed treatment to be focused on the symptomatic aneurysm. The light bulb sign was not present in any patient undergoing elective embolization. Aneurysm rupture with active extravasation occurred following embolization of the distal tumour circulation with PVA in four of 10 (40%) of the patients in the acute group and three of 13 (23%) patients in the elective group. Five patients required a subsequent embolization, three at a different site. Two patients in the elective group required repeat embolization of the target site, one for delayed haemorrhage and the other whose tumour did not shrink following the initial incomplete treatment. CONCLUSIONS: Embolization of renal angiomyolipoma produces durable results. The presence of the light bulb sign is a strong indicator of the site of haemorrhage within the kidney. We advocate using a combination of particulate material and coils, as embolization with PVA alone may predispose to acute haemorrhage occurring during or after embolization.

Does temporal artery biopsy influence the management of temporal arteritis?

BACKGROUND: Temporal arteritis (TA) is the commonest form of primary vasculitis. Symptoms are variable, and therefore the diagnosis (or exclusion) of TA is often difficult. Surgeons are frequently asked to perform a temporal artery biopsy (TAB), but whether the histological result actually influences clinical management is unclear. AIM: To assess whether, in routine clinical practice, a TAB affects clinical decision-making in patients with suspected TA. DESIGN: Retrospective audit. METHODS: All patients who underwent a TAB in a single hospital over a 2-year period were identified. This included patients referred from different specialist departments. Individual patient records were examined to document the TAB result, and in particular, the timings of commencement and discontinuation of corticosteroid therapy. RESULTS: A total of 44 patients were included. TAB was positive in seven patients and negative in 37. In 31, there was no change in their clinical management despite a negative biopsy result: 18 continued with corticosteroids for >6 months with a clinical diagnosis of TA, and in 13 patients a decision to stop steroids, or an alternative diagnosis, was made before the biopsy result was known. DISCUSSION: In this retrospective study, only a small number of TABs provided positive histological confirmation of TA, and in most patients undergoing TAB, there was little evidence that clinical decision-making with respect to corticosteroid therapy was influenced by the TAB result.

Synthesis and confirmation of structure for a new gibberellin, 2 beta-hydroxy-GA12 (GA110), from spinach and oil palm.

The identity of a new gibberellin (GA) in spinach and oil palm sap has been confirmed as 2 beta-hydroxy-GA12 (GA110) by comparisons of GC-mass spectral data obtained for the trimethylsilyl ether methyl ester derivatives with those of a synthetic sample prepared by means of a 24 step sequence from gibberellic acid; 2 beta-hydroxy-GA24 was also prepared. Experimental details for the latter part of the syntheses are described.

The efficacy of local anaesthetics administered by general dental practitioners.

AIM: To obtain empirical evidence for the efficacy of local anaesthesia in dentistry. DESIGN: Retrospective analysis of serial administrations of local anaesthesia. METHODS: Dentist and patient evaluations of the success of differing techniques (infiltration and block) of anaesthesia in a variety of general practice procedures. Results were analysed for correlation between dentist and patient using a 5-point scale. RESULTS: Complete data were analysed for 331 administrations. In the hands of experienced dentists over 93% of operations were assessed by both dentist and patient as comfortable or completely comfortable. Dentists were generally able to judge patient comfort (P < 0.001). Administrations requiring repeat injections were less comfortable. Dentists judged infiltration administrations more comfortable than block administrations (P < 0.001), but patient judgements of comfort failed to distinguish between differing techniques at the P < 0.05 level. CONCLUSIONS: Some variations in success rate exist between dentists the most dental procedures under local anaesthetic in general practice were assessed as being comfortable or better by both dentists and patients.

The effects of experience on the energy cost of wheelchair propulsion.

BACKGROUND: Gross mechanical efficiency (GE) of experienced wheelchair users is significantly higher than novice able-bodied individuals suggesting energy expenditure (EE) may be reduced in experienced individuals. With knowledge of the energy expended during wheelchair propulsion, nutritional recommendations can be provided for individuals in their early stages of rehabilitation and for habituated wheelchair users. AIM: To investigate the effects of experience on EE during wheelchair propulsion at fixed power outputs (PO's). DESIGN: This was an experimental study. SETTING: The experiment was conducted in a controlled University laboratory. POPULATION: Thirty-one individuals took part in this study. METHODS: Participants were assigned to a group in accordance to their wheelchair propulsion experience: 1) novice able-bodied individuals (NOV; N.=11), 2) able-bodied individuals habituated to three weeks practice (PRAC; N.=11) and 3) experienced paraplegic daily-wheelchair users (EXP; N.=9). Oxygen uptake, EE, GE% and HR were measured during wheelchair propulsion on a motorised treadmill at 10, 18 and 26 W. RESULTS: Energy expenditure analysis revealed a significant main effect of PO and group (P<0.01) and a significant group by PO interaction (P<0.01). Follow-up pair-wise comparisons revealed significantly lower EE in EXP compared to both other groups (P<0.01), but no difference was shown between NOV and PRAC (P=0.15). A lower relative EE of 20, 22 and 32% was reported in the EXP group compared to the NOV group at 10, 18 and 26 W respectively. In comparison to the PRAC group, the EE of the EXP group was 10, 16 and 26% lower in relative terms at the same PO's respectively. CONCLUSION: The EXP expended less EE compared to both NOV and PRAC. CLINICAL REHABILITATION IMPACT: This finding has great implications for nutritionists and health care professionals working in the field of physical activity and weight management since the EE is influenced by experience.

Measurement and repeatability of interrupter resistance in unsedated newborn infants.

Interrupter resistance (R(int)) is a useful measure of airway caliber in young children, but has not been well characterized in infants-in whom there are concerns about the accurate measurement of driving pressure. This study aimed to assess the feasibility and repeatability of measuring R(int) in unsedated newborn infants, and to explore alternative algorithms for calculating driving pressure. R(int) measurement was attempted in 28 healthy term newborn infants during natural sleep using the MicroRint device. Paired R(int) measurements were achieved in 24 infants, but after screening of waveforms only 15 infants had at least 5 technically acceptable waveforms on both measurements. R(int) values obtained were comparable with reported values for airflow resistance in newborns using other methods. However, the repeatability coefficient (CR) was much higher than reported values in preschool children using standard back-extrapolation algorithms, with CR 2.47 KPa L(-1) sec (unscreened) and 2.93 KPa L(-1) sec (screened). Other algorithms gave only marginally better repeatability, with all CR values over 50% of the mean R(int) value. Using current commercially available equipment, R(int) is too poorly repeatable to be a reliable measurement of airflow resistance in newborn infants. Lower deadspace equipment is needed, but anatomical and physiological factors in the infant are also important.

Efficiency of wheelchair propulsion and effects of strategy.

The purpose of this study was to determine the contributions of arm frequency and propulsion mode on the internal work during submaximal wheelchair propulsion. Twelve able-bodied participants performed a V.O (2) peak test on a wheelchair ergometer. On a separate occasion, six (4 min) submaximal exercise conditions employing two modes of propulsion (synchronous, SYN vs. asynchronous, ASY) at arm frequencies of 40 and 80 rev . min (-1) were performed at 1.2 m . s (-1) and 1.7 m . s (-1). These conditions resulted in three push strategy combinations (ASY [20 : 20], SYN [40 : 40] & ASY [40 : 40]) at two speeds. Gross, net, work and delta efficiency were determined. The cost of unloaded exercise was significantly lower for the ASY [20 : 20] than both ASY and SYN [40 : 40] (0.49 vs. 0.58 and 0.57 L . min (-1), respectively). All the efficiency indices decreased as velocity increased (p < 0.01). ASY [20 : 20] was the least efficient (gross and work) mode (4.2 +/- 0.4 % and 6.2 +/- 0.8 % respectively). Comparison of equal arm frequencies (ASY [40 : 40] vs. SYN [40 : 40]); found the efficiency to be lower for ASY propulsion (p < 0.05). Under the current testing conditions SYN propulsion mode offers greater efficiency during wheelchair propulsion.

Gibberellins and leaf expansion in near-isogenic wheat lines containing Rht1 and Rht3 dwarfing alleles.

In near-isogenic lines of winter wheat (Triticum aestivum L. cv. Maris Huntsman) grown at 20° C under long days the reduced-height genes, Rht1 (semi-dwarf) and Rht3 (dwarf) reduced the rate of extension of leaf 2 by 12% and 52%, respectively, compared with corresponding rht (tall) lines. Lowering the growing temperature from 20° to 10° C reduced the rate of linear extension of leaf 2 by 2.5-fold (60% reduction) in the rht3 line but by only 1.6-fold (36% reduction) in the Rht3 line. For both genotypes, the duration of leaf expansion was greater at the lower temperature so that final leaf length was reduced by only 35% in the rht3 line and was similar in the Rht3 line at both temperatures. Seedlings of the rht3 (tall) line growing at 20° C responded positively to root-applied gibberellin A1 (GA1) in the range 1-10 µM GA1; there was a linear increase in sheath length of leaf 1 whereas the Rht3 (dwarf) line remained unresponsive. Gibberellins A1, 3, 4, 8, 19, 20, 29, 34, 44 and 53 were identified by full-scan gas chromatography-mass spectrometry in aseptically grown 4-d-old shoots of the Rht3 line. In 12-d-old seedlings grown at 20° C, there were fourfold and 24-fold increases in the concentration of GA1 in the leaf expansion zone of Rht1 and Rht3 lines, respectively, compared with corresponding rht lines. Although GA3 was present at a similar level to GA1 in the rht3 (tall) line it accumulated only fivefold in the Rht3 (dwarf) line. The steady-state pool sizes of endogenous GAs were GA19 ≫ GA20 = GA1 in the GA-responsive rht3 line whereas in the GA non-responsive Rht3 line the content of GA19≈ GA20 ⋘ GA1. It is proposed that one of the consequences of GA1 action is suppression of GA19-oxidase activity such that the conversion of GA19 to GA20 becomes a rate-limiting step on the pathway to GA1 in GA-responsive lines. In the GA-non-responsive Rht lines it is suggested that GA19 oxidase is not downregulated to the same extent and GA1 accumulates before the next rate-limiting step on the pathway, its 2ß-hydroxylation to GA8. The steady-state pool sizes of GA19, 20, 1, 3 and 8 were similar in developmentally equivalent tissues of the rht3 (tall) line growing at 10° C and 20° C despite a 2.5-fold difference in the rate of leaf expansion. In contrast, in the Rht3 (dwarf) line, the extent of accumulation of GA1 reflected the severity of the phenotype at the two temperatures with slower growing tissues accumulating less, not more, GA1. These results are interpreted as supporting the proposed model of regulation of the GA-biosynthetic pathway rather than previous suggestions that GA1 accumulates in GA-insensitive dwarfs as a consequence of reduced growth rates.

T-DNA genes to study plant development: precocious tuberisation and enhanced cytokinins in A. tumefaciens transformed potato.

Potato Line Mb1501B is a derivative of the cultivar Maris Bard (Solanum tuberosum), transformed with T-DNA from A. tumefaciens strain LBA1501. In culture it grew as frequently branching stunted shoots with a basal callus, lacking roots. These shoots did not form tubers. When grafted, Mb1501B shoots gradually became morphologically more normal and aerial tubers formed readily. Cultured Mb1501B shoots contained 100-200-fold higher concentrations of the biologically-active cytokinins zeatin, zeatin riboside and their corresponding side-chain o-glucosides than untransformed Maris Bard shoots. Cultured Mb1501B shoots contained approximately a 3-fold lower concentration of indole acetic acid (IAA). In grafted Mb1501B plants a 3-10-fold higher concentration of the active cytokinins was found compared with untransformed plants and no difference in IAA concentration.

Endogenous abscisic acid in relation to photoperiodically induced bud dormancy.

The abscisic acid contents of birch, maple and sycamore plants growing under long and short photoperiods were measured by gas-liquid chromatography. No increase was observed in the abscisic acid content of extracts when plants were transferred to dormancy-inducing conditions.

Propoxyphene dependence: problems in management.

Propoxyphene dependence presents a difficult treatment problem: the patients' subjective discomfort and concomitant craving during gradual withdrawal of the drug is more intense and more poorly tolerated than that observed with other narcotic analgesic agents. Of the six patients we describe, only one has achieved successful detoxification.