Description:
Static stretching (SS) is widely used in warm-ups before training and competition. A growing amount of research, however, has demonstrated that SS can impair muscle performance, leading to a reevaluation of optimal warm-up protocols. This commentary discusses many of the methodological issues that can influence conclusions about the acute effects of SS on performance. One difficulty in interpreting the literature is the lack of control or communication about the volume and intensity of the various stretching treatments used. Another major issue is the failure of many researchers to evaluate SS as it is used in practice, particularly the interaction with the other general and sport-specific components of the warm-up. Acute warm-up effects on performance should be considered in conjunction with potential effects on injury prevention. Future directions in research include optimizing general and sport-specific warm-ups, time course of physiological and performance effects, and individualization of warm-ups according to fitness and skill level.
Description:
A purpose of this study was to determine if pre-season anthropometric and physiological measures were significantly different for the players from one Australian Football League (AFL) club selected to play in the first game of the season compared to the players not selected. Another purpose was to compare fitness test results for defenders, forwards and mid-fielders in the same AFL club. Thirty-four players were tested for isolated quadriceps and hamstrings strength, leg extensor muscle strength and power, upper body strength, sprinting speed, vertical jump (VJ), endurance, skinfolds and hamstring flexibility. The starters who were selected to play the first game were a significantly older and more experienced playing group, and were significantly better (p < 0.05) in measures of leg power, sprinting speed and the distance covered in the Yo Yo intermittent recovery test compared to the non-starters. Although there were trends for the superiority of the starters, the differences in lower and upper body strength, VJ and predicted VO(2)max were nonsignificant. The forwards generally produced the worst fitness scores of the playing positions with the midfielders having significantly lower skinfolds and the defenders possessing better hamstring strength and VJ compared to the forwards. It was concluded that some fitness qualities can differentiate between starters and non-starters, at least in one AFL club. Comparisons of playing positions and the development of fitness norms for AFL players require further research.
Description:
A purpose of this study was to determine if pre-season anthropometric and physiological measures were significantly different for the players from one Australian Football League (AFL) club selected to play in the first game of the season compared to the players not selected. Another purpose was to compare fitness test results for defenders, forwards and mid-fielders in the same AFL club. Thirty-four players were tested for isolated quadriceps and hamstrings strength, leg extensor muscle strength and power, upper body strength, sprinting speed, vertical jump (VJ), endurance, skinfolds and hamstring flexibility. The starters who were selected to play the first game were a significantly older and more experienced playing group, and were significantly better (p < 0.05) in measures of leg power, sprinting speed and the distance covered in the Yo Yo intermittent recovery test compared to the non-starters. Although there were trends for the superiority of the starters, the differences in lower and upper body strength, VJ and predicted VO(2)max were nonsignificant. The forwards generally produced the worst fitness scores of the playing positions with the midfielders having significantly lower skinfolds and the defenders possessing better hamstring strength and VJ compared to the forwards. It was concluded that some fitness qualities can differentiate between starters and non-starters, at least in one AFL club. Comparisons of playing positions and the development of fitness norms for AFL players require further research.
Description:
The purpose of this research was to determine the effect of static stretching in a warm-up on hip flexor and quadriceps flexibility as measured by a modified Thomas test and on range of motion (ROM) of the leg and foot speed at impact in kicking a football with maximum effort. Sixteen Australian Rules (AR) footballers performed two different warm-ups on different days. One warm-up involved five minutes of sub-maximum running followed by seven practice kicks, while the other also included 4.5 minutes static stretching of the hip flexors and quadriceps after the running. A modified Thomas test was conduced before and after each warm-up. Players performed maximum effort drop punt kicks into a net while being videotaped to determine the ROM of the kicking leg and foot speed at impact with the ball. There were no significant changes in flexibility (p>0.05) as a result of either warm-up and there were no significant differences between the warm-ups in the kicking variables (p>0.05). It was concluded that the Thomas test may not have been sensitive to possible acute changes in flexibility from the warm-ups, and that stretching had no influence on kicking ROM or foot speed, possibly because of the complexity of the kicking skill.
Description:
The purpose of this research was to determine the effect of static stretching in a warm-up on hip flexor and quadriceps flexibility as measured by a modified Thomas test and on range of motion (ROM) of the leg and foot speed at impact in kicking a football with maximum effort. Sixteen Australian Rules (AR) footballers performed two different warm-ups on different days. One warm-up involved five minutes of sub-maximum running followed by seven practice kicks, while the other also included 4.5 minutes static stretching of the hip flexors and quadriceps after the running. A modified Thomas test was conduced before and after each warm-up. Players performed maximum effort drop punt kicks into a net while being videotaped to determine the ROM of the kicking leg and foot speed at impact with the ball. There were no significant changes in flexibility (p>0.05) as a result of either warm-up and there were no significant differences between the warm-ups in the kicking variables (p>0.05). It was concluded that the Thomas test may not have been sensitive to possible acute changes in flexibility from the warm-ups, and that stretching had no influence on kicking ROM or foot speed, possibly because of the complexity of the kicking skill.
Description:
The purpose of this investigation was to examine power performance in jump squats when using the complex and contrast training methods. Eleven (n = 11) women participated in a familiarization session and in three randomly ordered testing sessions. One session involved completing sets of power exercises (jump squats) before sets of half squats (traditional method). The second session involved sets of half squats before sets of jump squats (complex method). A third session involved the alternation of sets of half squats and jump squats (contrast method). No significant difference in jump squat performance between each of the training methods was found. There was a significant difference (p < 0.05) in the first set of each session, with the complex method having a significantly lower peak power. Further, there was a significant difference (p < 0.05) in performance changes between the higher and lower strength groups, with the higher strength group having a greater improvement in performance using the contrast training method compared with the traditional method. It was concluded that contrast training is advantageous for increasing power output but only for athletes with relatively high strength levels.
Description:
In this project, an in-situ soil treatment technique based on electrokinetics was tested in order to identify the potential of this approach to modify the engineering properties of salt affected soils.
Description:
Purpose: The main purpose of this study was to determine the relationships between countermovement jump (CMJ) variables and acceleration and maximum speed performance. Methods: Twenty-three elite Australian football players were tested on a CMJ, which yielded several kinematic and kinetic variables describing leg muscle function. A 40 m sprint was also conducted to assess acceleration (10 m time) and an estimate of maximum speed (flying 20 m time). Players from one Australian Football League (AFL) club were tested and Pearson correlations for CMJ variables and sprint performance were calculated. Results: Jump height, peak velocity, peak force, and peak power had less than 50% common variance, and therefore represented independent expressions of CMJ performance. Generally, the correlations between CMJ variables and sprinting performance were stronger for maximum speed (small to large effect sizes) than for acceleration (trivial to moderate sizes). The variable that produced the strongest correlation with acceleration was jump height (r = -0.430, P = .041) and with maximum speed was peak power/weight (r = -0.649, P = .001). Conclusions: The results indicate that if an integrated system comprising a position transducer and a force platform is available for CMJ assessment, jump height and peak power/weight are useful variables to describe leg muscle explosive function for athletes who perform sprints.
Description:
The tactical and technical components of training become a primary emphasis, leaving less time for targeted development of physical qualities that underpin performance during the competition phase of a training program. A deemphasis on physical preparation during the in-season training phase may make athletes more susceptible to injury and decrease performance on the field. Two weeks prior to the start and one week following the conclusion of the 16-week collegiate lacrosse season, lower body force production was assessed in eight National Collegiate Athletic Association (NCAA) Division I Men's Lacrosse athletes. Lower body force production capabilities were determined via the performance of countermovement jumps (CMJ) and drop jumps (DJ) performed on a force plate and isokinetic strength testing of the quadriceps and hamstring muscle groups across three velocities. Isokinetic strength of the hamstrings and the hamstring to quadriceps strength ratio were maintained or increased over the course of the competition phase of training. Relative peak force obtained from the CMJ and the reactive strength index from the DJ decreased significantly over the season. The maintenance of isokinetic strength and the decrease in CMJ and DJ performance may indicate the presence of neuromuscular fatigue that accumulated over the course of the season.
Description:
The tactical and technical components of training become a primary emphasis, leaving less time for targeted development of physical qualities that underpin performance during the competition phase of a training program. A deemphasis on physical preparation during the in-season training phase may make athletes more susceptible to injury and decrease performance on the field. Two weeks prior to the start and one week following the conclusion of the 16-week collegiate lacrosse season, lower body force production was assessed in eight National Collegiate Athletic Association (NCAA) Division I Men's Lacrosse athletes. Lower body force production capabilities were determined via the performance of countermovement jumps (CMJ) and drop jumps (DJ) performed on a force plate and isokinetic strength testing of the quadriceps and hamstring muscle groups across three velocities. Isokinetic strength of the hamstrings and the hamstring to quadriceps strength ratio were maintained or increased over the course of the competition phase of training. Relative peak force obtained from the CMJ and the reactive strength index from the DJ decreased significantly over the season. The maintenance of isokinetic strength and the decrease in CMJ and DJ performance may indicate the presence of neuromuscular fatigue that accumulated over the course of the season.
Description:
Water treatment plants (WTP) in the City of Manaus, Brazil, generate tons of sludge daily, which are then disposed of in landfills and main watercourses, particularly two important Amazonian Rivers: the blackwater Negro River and the pale sandy-colored water Solimoes River. Because WTP-based sludges are rich in silicon and aluminum, they have been employed in the synthesis of geopolymers - alkaline activated inorganic polymers consisting of silicate and aluminosilicate chains. This paper reports the results of a geopolymeric synthesis process in which calcined sludge was explored as a source of silica and alumina. In this research, a laboratory testing program was developed to characterize the waste material generated from a water treatment plant in Manaus, whose intake water is influenced by the above referred rivers. Sample preparation involved kiln drying at 110 degrees C for 8 h, grinding in ball mill for 2 h, and calcination at 750 degrees C for 6 h. The calcined sludge was used as precursor, and potassium hydroxide added as activating alkali. Two geopolymers, one from each sludge source, were prepared following identical procedures. The chemical, compositional, morphological, thermal and mechanical properties of the fresh and hardened geopolymers were characterized. The geopolymers reached uniaxial compressive strengths of over 50 MPa at 28 days. Calcination conveyed more refined properties to the sludge-based geopolymers, akin to metakaolin-based geopolymers. The results presented herein support the technical feasibility of geopolymer synthesis in the lab scale.
Description:
The aim of the present study was to establish a relationship between the diurnal variations of testosterone and cortisol with the circadian rhythm of strength and power performance. Changes in salivary cortisol and salivary testosterone were measured after two different modes of maximal exercise (back squat and maximal 5 m sprint) at two different times of day to assess diurnal fluctuations. Seventeen physically active males volunteered as subjects. A randomized cross-over design was utilized and participants were allocated to a maximal back squat protocol at 09:00 and 17:00 h, and a maximal 5 m sprint protocol at 09:00 and 17:00 h separated by at least 48 h. Saliva samples were collected before exercise, at 5 and 60 min post exercise. Exercise performance displayed no time of day effect. No significant effect of exercise mode or time of day was observed in cortisol or testosterone concentrations. Cortisol concentrations were higher in the morning (p<0.001). Testosterone did not exhibit a significant time of day effect however, higher levels tended to be observed at 09:00 h. The data suggest that non weight trained individuals do not display a time of day effect for maximum squat or 5 m sprint performance, or the subsequent salivary hormonal response.
Description:
The purpose of this investigation was to determine whether weightlifting actions are a viable method for improving athletic performance among weaker, inexperienced lifters when compared with individuals with a greater power clean (PC) result, and hence weightlifting ability and experience. Two groups of males with distinctly different PC performances (higher performance [HP]: N = 8; body mass [BM] = 78.1 +/- 4.0 kg; 1 repetition maximum [1RM] PC = 1.08 +/- 0.09 kg.BM-1; lower performance [LP]: N = 8; BM = 82.6 +/- 14.0 kg; 1RM PC = 0.78 +/- 0.1 kg.BM-1) and resistance training age (HP: resistance training experience = 3.5 +/- 1.2 years; LP: resistance training experience = 1.44 +/- 1.50 years) undertook 10 weeks of training involving weightlifting derivatives, in addition to supplemental ballistic and plyometric exercises. Testing of athletic performance (represented by measures derived from the countermovement jump) occurred at baseline, after 5 weeks of training, and after 10 weeks of training. Both groups significantly improved across the majority of outcome variables after training (Hedges' g = 0.98-2.55, p <= 0.01-0.05). Only the HP participants experienced significant changes at midtest (g = 0.99-1.27, p <= 0.01-0.05), whereas no significant changes were revealed between midtest and posttest in this group. In contrast to this, the LP participants displayed a significant improvement in relative impulse (g = 1.39, p < 0.01) and rate of force development (g = 1.91, p < 0.01) during this final period (p < 0.01). As weaker, inexperienced lifters underwent a significant and meaningful enhancement in maximal neuromuscular measures after weightlifting derivative-focused training, practitioners should consider early implementation of such exercises. However, it is important for coaches to note that a delayed training effect might be present in weaker, less experienced lifters.
Description:
Although strength and conditioning of cricket pace bowlers has become more specialized in recent times, little is understood about the interplay between physical capacities, pace bowling kinematics, and pace bowling skill measures. This study sought to determine these interrelationships. Thirty-one male club-standard pace bowlers completed 3 test sessions on separate occasions 4-7 days apart. The first testing session comprised an 8-over pace bowling assessment, where bowling skill and selected bowling kinematics were measured. A physical test battery was completed over the remaining 2 sessions. Peak and mean ball release (BR) speed were related with 1 repetition maximum pull-up strength (r(s) = 0.56, p = 0.005) and correlated with 20-m sprint time (r(s) = -0.42, p = 0.022; r(s) = -0.37, p = 0.044, respectively). Mean radial error was associated with 10-m and 20-m sprint times (r(s) = 0.41, p = 0.030; r(s) = 0.38, p = 0.037, respectively), and correlated with height and peak power from 3 countermovement jumps (CMJs) (r(s) = -0.39, p = 0.036; r(s) = -0.41, p = 0.031, respectively), and mean peak power from 20 CMJs (r(s) = -0.45, p = 0.020). Bivariate variable error was correlated with front-leg extension angle at BR (r(s) = 0.41, p = 0.036), and also with approach speed (r(s) = -0.36, p = 0.050). These relationships may assist strength and conditioning coaches in designing more effective training programs to enhance bowling speed and accuracy. Training interventions are warranted, however, to validate these associations.
Description:
Little is known of how agility events occur in the sport of Australian football (AF). As a result, appropriate training and testing methods are unknown. This thesis investigated 1v1 agility in AF to evaluate alternative methods for training and testing agility. The thesis was undertaken in three studies. Study one investigated if training and testing practices used in elite AF align with the demands of competition. A notational analysis revealed substantial variation in movement patterns used by, and the cognitive demands of, athletes in agility events. A survey of high-performance managers in the AFL revealed that a mixture of open and closed training methods are used in elite AF, and that subjective agility assessment is preferred to formal testing. Study two assessed the reliability and ecological validity of a field-based test of attacking and defending agility for AF. The text exhibited excellent inter-rater and intra-rater reliability, as well as moderate test-retest reliability. Characteristics of the test were compared to the notational analysis to assess the ecological validity of the test. While the test did not fully replicate the agility demands of AF, the test improved ecological validity when compared to previous tests described in the literature. Study three evaluated the effectiveness of a four-week 1v1 training intervention for improving attacking and defending agility in Australian footballers. In addition, the study assessed the crossover of attacking training to defending agility and defending training to attacking agility. Improvements in attacking agility were found which were greater for attacking-trained athletes. However, no improvements in defending agility were realised. This thesis indicates that 1v1 training and testing is suitable for assessing and developing agility in Australian footballers. However, 1v1 training may be more suitable for improving attacking agility. Further, agility is context-specific, and testing and training should consider the role of the athlete.
Description:
Little is known of how agility events occur in the sport of Australian football (AF). As a result, appropriate training and testing methods are unknown. This thesis investigated 1v1 agility in AF to evaluate alternative methods for training and testing agility. The thesis was undertaken in three studies. Study one investigated if training and testing practices used in elite AF align with the demands of competition. A notational analysis revealed substantial variation in movement patterns used by, and the cognitive demands of, athletes in agility events. A survey of high-performance managers in the AFL revealed that a mixture of open and closed training methods are used in elite AF, and that subjective agility assessment is preferred to formal testing. Study two assessed the reliability and ecological validity of a field-based test of attacking and defending agility for AF. The text exhibited excellent inter-rater and intra-rater reliability, as well as moderate test-retest reliability. Characteristics of the test were compared to the notational analysis to assess the ecological validity of the test. While the test did not fully replicate the agility demands of AF, the test improved ecological validity when compared to previous tests described in the literature. Study three evaluated the effectiveness of a four-week 1v1 training intervention for improving attacking and defending agility in Australian footballers. In addition, the study assessed the crossover of attacking training to defending agility and defending training to attacking agility. Improvements in attacking agility were found which were greater for attacking-trained athletes. However, no improvements in defending agility were realised. This thesis indicates that 1v1 training and testing is suitable for assessing and developing agility in Australian footballers. However, 1v1 training may be more suitable for improving attacking agility. Further, agility is context-specific, and testing and training should consider the role of the athlete.
Description:
Generation of negative excess pore-water pressure (NEPWP) due to the excavation of saturated soils under undrained conditions and the dissipation that follows over time may result in different short- and long-term slope instability. The NEPWP generated due to excavation gradually decreases towards equilibrium or, in some cases, steady seepage. Hence, total pore-water pressures immediately after excavation are lower than the ultimate equilibrium values, leading to a reduction of the average effective stresses in the slope and subsequently threatening stability in the long term. In this research study, the stability of three benchmark civil and mining excavations has been studied, considering the effects of the generation and dissipation of NEPWP. A series of numerical simulations are conducted to determine the role of in situ stresses and time in NEPWP dissipation as well as the consequent effects on the stability of the excavated slopes. To conduct a realistic time-dependent transient analysis, fully coupled hydro-geomechanical formulation has been employed. Results show that in general, higher removal of stress levels lead to higher NEPWP generation and higher factor of safety values in the short term. Thereafter, the dissipation of NEPWP threatens the long-term stability of the excavation.
Description:
Generation of negative excess pore-water pressure (NEPWP) due to the excavation of saturated soils under undrained conditions and the dissipation that follows over time may result in different short- and long-term slope instability. The NEPWP generated due to excavation gradually decreases towards equilibrium or, in some cases, steady seepage. Hence, total pore-water pressures immediately after excavation are lower than the ultimate equilibrium values, leading to a reduction of the average effective stresses in the slope and subsequently threatening stability in the long term. In this research study, the stability of three benchmark civil and mining excavations has been studied, considering the effects of the generation and dissipation of NEPWP. A series of numerical simulations are conducted to determine the role of in situ stresses and time in NEPWP dissipation as well as the consequent effects on the stability of the excavated slopes. To conduct a realistic time-dependent transient analysis, fully coupled hydro-geomechanical formulation has been employed. Results show that in general, higher removal of stress levels lead to higher NEPWP generation and higher factor of safety values in the short term. Thereafter, the dissipation of NEPWP threatens the long-term stability of the excavation.
Caucasian and south Asian men show equivalent improvements in surrogate biomarkers of cardiovascular and metabolic health following 6-weeks of supervised resistance training
Description:
Background: The South Asian population have greater cardiovascular risk than their age-matched Caucasian counterparts, characterized by unfavorable biomarkers. South Asians may also be partially resistant to the pleiotropic benefits of physical activity on cardiovascular health. There is a current absence of studies that compare markers of cardio-metabolic health between Caucasians and South Asians employing resistance exercise. This study set out to compare the response in biomarkers of cardio-metabolic health in Caucasians and South Asians in response to resistance exercise. Methods: Caucasian (n=15, 25.5 ± 4.8 yrs) and South Asian (n=13, 25.4 ± 7.0 yrs) males completed a 6-week progressive resistance exercise protocol. Fasting blood glucose, insulin, and their product insulin resistance (HOMA-IR), triglycerides (TRIGS), low density lipoprotein (LDL), high density lipoprotein (HDL), total cholesterol (TC), vascular endothelial growth factor (VEGF), asymmetric dimythylarginine (ADMA), L-arginine (L-ARG) and C-reactive protein (CRP) were established at baseline and following resistance exercise. Results: There were significant improvements in fasting glucose, TC, LDL, HDL and VEGF in both groups following resistance exercise ( p<0.05, for all). No change was observed in insulin, HOMA-IR, TRIGS, ADMA, L-ARG following resistance exercise ( p>0.05, in both groups). CRP increased in the South Asian group ( p<0.05) but not the Caucasian group ( p>0.05) Conclusions: The cardio-metabolic response to resistance exercise is comparable in young Caucasian and South Asian males though inflammatory response to exercise may be prolonged in South Asians.
Description:
Background: The South Asian population have greater cardiovascular risk than their age-matched Caucasian counterparts, characterized by unfavorable biomarkers. South Asians may also be partially resistant to the pleiotropic benefits of physical activity on cardiovascular health. There is a current absence of studies that compare markers of cardio-metabolic health between Caucasians and South Asians employing resistance exercise. This study set out to compare the response in biomarkers of cardio-metabolic health in Caucasians and South Asians in response to resistance exercise. Methods: Caucasian (n=15, 25.5 ± 4.8 yrs) and South Asian (n=13, 25.4 ± 7.0 yrs) males completed a 6-week progressive resistance exercise protocol. Fasting blood glucose, insulin, and their product insulin resistance (HOMA-IR), triglycerides (TRIGS), low density lipoprotein (LDL), high density lipoprotein (HDL), total cholesterol (TC), vascular endothelial growth factor (VEGF), asymmetric dimythylarginine (ADMA), L-arginine (L-ARG) and C-reactive protein (CRP) were established at baseline and following resistance exercise. Results: There were significant improvements in fasting glucose, TC, LDL, HDL and VEGF in both groups following resistance exercise ( p<0.05, for all). No change was observed in insulin, HOMA-IR, TRIGS, ADMA, L-ARG following resistance exercise ( p>0.05, in both groups). CRP increased in the South Asian group ( p<0.05) but not the Caucasian group ( p>0.05) Conclusions: The cardio-metabolic response to resistance exercise is comparable in young Caucasian and South Asian males though inflammatory response to exercise may be prolonged in South Asians.