Rebecca Cross

Player sensitivity to changes in string tension in a tennis racket

Forty-one advanced recreational tennis players were tested to determine their ability to detect differences in string tension in a tennis racket. Subjects were given pairs of rackets that varied in tension by up to 98 N (10 kg) and were asked whether they noticed a difference in tension and if so, which racket was strung at a higher tension. Only 11 (27%) of those tested could correctly identify a tension difference of 5 kg (11 lb) or less. Fifteen (37%) could not pick a difference of 10 kg (22 lb). To examine the importance of sound as a means of discrimination, an additional test was undertaken where participants wore earplugs. Of the 26 subjects undertaking this additional test, only 6 (23%) were successful. It was concluded that advanced recreational tennis players demonstrated limited ability to correctly identify differences in string tension and that impact sound was an important factor for those participants who were successful at various levels of discrimination.

Passive heating following the prematch warm-up in soccer: examining the time-course of changes in muscle temperature and contractile function.

This study examined changes in muscle temperature, electrically evoked muscle contractile properties, and voluntary power before and after a soccer specific active warm‐up and subsequent rest period. Ten amateur soccer players performed two experimental sessions that involved performance of a modified FIFA 11+ soccer specific warm‐up, followed by a 12.5‐min rest period where participants were required to wear either normal clothing or a passive electrical heating garment was applied to the upper thigh muscles. Assessments around the warm‐up and cool‐down included measures of maximal torque, rate of torque development, muscle temperature (Tm), and electrically evoked measures of quadriceps contractile function. Tm was increased after the warm‐up by 3.2 ± 0.7°C (P < 0.001). Voluntary and evoked rates of torque development increased after the warm‐up between 20% and 30% (P < 0.05), despite declines in both maximal voluntary torque and voluntary activation (P < 0.05). Application of a passive heating garment in the cool‐down period after the warm‐up did not effect variables measured. While Tm was reduced by 1.4 ± 0.4°C after the rest period (P < 0.001), this value was still higher than pre warm‐up levels. Voluntary and evoked rate of torque development remained elevated from pre warm‐up levels at the end of the cool‐down (P < 0.05). The soccer specific warm‐up elevated muscle temperature by 3.2°C and was associated with concomitant increases of between 20% and 30% in voluntary rate of torque development, which seems explained by elevations in rate‐dependent measures of intrinsic muscle contractile function. Application of a passive heating garment did not attenuate declines in muscle temperature during a 12.5‐min rest period.

The fatigue of a full body resistance exercise session in trained men

OBJECTIVES We examined the fatigue and recovery for 48h following a full-body resistance exercise session in trained men. DESIGN Experimental cross-sectional study. METHODS Eight resistance trained men volunteered to participate (mean±SD; age 27.0±6.0 years, height 1.79±0.05m, weight 81.8±6.8kg, training experience 7.8±5.0 years). Fatigue and pain was measured before, after, 1h post, 24h and 48h post the full-body resistance exercise session, which was based on in-season models used in contact team sports (e.g. AFL, NRL). Other measures included maximal torque and rate of torque development, central motor output (quadriceps muscle activation, voluntary activation, H-reflexes), and muscle contractility (evoked twitch responses). Linear mixed-model ANOVA procedures were used for data analysis. RESULTS Fatigue, soreness, and muscle pain did not return to pre-exercise levels until after 48h rest. Quadriceps maximal torque and muscle contractility were reduced from pre-exercise (p<0.01), and did not return to pre-exercise levels until 24h. Early rates of torque development and muscle activation were unchanged. The amplitude and slope of the normalized quadriceps H-reflex was higher immediately after exercise (p<0.05). CONCLUSIONS Full-body resistance exercise including multiple lower limb movements immediately reduced maximal torque, muscle contractility, and increased pain. While recovery of voluntary and evoked torque was complete within a day, 48h rest was required for fatigue and pain to return to baseline. Maximal voluntary effort may be compromised for lower-limb training (i.e. sprinting, jumping) prescribed in the 48h after the session.

Acute attenuation of fatigue after sodium bicarbonate supplementation does not manifest into greater training adaptations after 10-weeks of resistance training exercise

Purpose In two concurrent studies, we aimed to a) confirm the acute effect of 0.3 g·kg-1 body weight (BW) sodium bicarbonate (NaHCO3) supplementation on central and peripheral mechanisms associated with explosive power (Study 1) and b) determine whether chronic NaHCO3 supplementation would improve the adaptive response of the neuromuscular system during a 10-week resistance training program (Study 2). Methods Eight resistance trained participants volunteered after providing written consent. The experimental design consisted of a week of baseline testing, followed by ten weeks of training with progress measures performed in Week 5. Study 1 involved neuromuscular measurements before and after the leg extension portion of a power based training session performed in Week 1. Changes in maximal torque (MVT) and rates of torque development (RTD), along with other variables derived from femoral nerve stimulation (e.g. voluntary activation, neural recruitment) were analysed to determine the extent of fatigue under NaHCO3 or placebo conditions. Changes in these same variables, coupled with functional 1-repetition maximum leg extension strength, were measured in Study 2 from baseline (Week 0) to Week 5, and again at Week 10. Results and conclusion In Study 1, we observed a decline after the leg extension task in both MVT (~ 30%) and rates of torque production (RTD) irrespective of acid-base status, however the decline in maximal RTD (RTDMAX) was nearly 20% less in the NaHCO3 condition when compared to placebo (mean difference of 294.8 ± 133.4 Nm·s-1 (95% CI -583.1 to -6.5 Nm, p < 0.05)). The primary finding in Study 2, however, suggests that introducing NaHCO3 repeatedly during a 10-week RT program does not confer any additional benefit to the mechanisms (and subsequent adaptive processes) related to explosive power production.

Weed hygiene practices in rural industries and public land management: Variable knowledge, patchy implementation, inconsistent coordination

Weed management science and practice largely focuses on eradicating, containing and reducing existing weed populations; the focus is on plants in situ. More recently, the redefinition of biosecurity to include weeds has seen greater attention paid to preventing the introduction of weeds to previously uninfested areas within countries. Thus weed hygiene has come to the fore, with a growing number of publications recommending a diverse range of practices to minimise the spread of weeds across farm, regional and state boundaries. Yet little is known about the uptake of weed hygiene practices. The aim of this paper is to evaluate the extent to which best practice weed hygiene is being implemented on, across and along private and public lands. Telephone interviews were conducted with 54 private and public land managers, weed contractors, and agricultural transport operators in New South Wales, Australia. Vehicle hygiene was commonly undertaken across all stakeholder groups when it was consistent with other goals, requirements or norms. Other practices, such as sequencing harvesting from least to most weedy paddocks or including weed hygiene clauses in contracts were often known, but rarely practiced because of the onerous labour and financial costs or concerns about social etiquette. Individual commitment to weed hygiene efforts were also undermined by intra and inter-organisational coordination challenges. Public debate and assessment are needed on the benefits and costs to society of weed hygiene compared to in situ weed control to determine where best to invest limited time and resources.

Exploring Agroecological Sustainability: Unearthing Innovators and Documenting a Community of Practice in Southeast Australia

ABSTRACT In this article we describe a movement to regenerate and sustainably use native grasslands using innovative grazing and cropping strategies. We find that this movement has the essential characteristics of a “community of practice” (COP) and is a strong example of a bottom-up transition toward a sustainable agroecological farming system. This COP was identified and described using participatory rural appraisals followed by biophysical and sociocultural studies with active COP members. Using these multiple mixed-method approaches helped characterize the COP’s many layers, revealing how and why it is driven and fashioned by innovators who collaborate via joint enterprise, mutual engagement, and shared repertoire. Holistic Management, Grazing for Profit, and Stipa Native Grasses Association were the key enabling programs/associations for the COP, which, like other agroecological movements, exists on the margins of conventional agri-innovation systems and endures with little public acknowledgment or support. It is a potent grass-roots example of adaptive farm management that generates optimism in the farming families involved, and challenges existing research and extension paradigms regarding both innovation and practice change.