Effects of plyometric training on achilles tendon properties and shuttle running during a simulated cricket batting innings.

The aim of this study was to determine whether intermittent shuttle running times (during a prolonged, simulated cricket batting innings) and Achilles tendon properties were affected by 8 weeks of plyometric training (PLYO, n = 7) or normal preseason (control [CON], n = 8). Turn (5-0-5-m agility) and 5-m sprint times were assessed using timing gates. Achilles tendon properties were determined using dynamometry, ultrasonography, and musculoskeletal geometry. Countermovement and squat jump heights were also assessed before and after training. Mean 5-0-5-m turn time did not significantly change in PLYO or CON (pre vs. post: 2.25 ± 0.08 vs. 2.22 ± 0.07 and 2.26 ± 0.06 vs. 2.25 ± 0.08 seconds, respectively). Mean 5-m sprint time did not significantly change in PLYO or CON (pre vs. post: 0.85 ± 0.02 vs. 0.84 ± 0.02 and 0.85 ± 0.03 vs. 0.85 ± 0.02 seconds, respectively). However, inferences from the smallest worthwhile change suggested that PLYO had a 51-72% chance of positive effects but only 6-15% chance of detrimental effects on shuttle running times. Jump heights only increased in PLYO (9.1-11.0%, p < 0.050). Achilles tendon mechanical properties (force, stiffness, elastic energy, strain, modulus) did not change in PLYO or CON. However, Achilles tendon cross-sectional area increased in PLYO (pre vs. post: 70 ± 7 vs. 79 ± 8 mm, p < 0.01) but not CON (77 ± 4 vs. 77 ± 5 mm, p > 0.050). In conclusion, plyometric training had possible benefits on intermittent shuttle running times and improved jump performance. Also, plyometric training increased tendon cross-sectional area, but further investigation is required to determine whether this translates to decreased injury risk.

Achilles tendon mechanical properties after both prolonged continuous running and prolonged intermittent shuttle running in cricket batting.

Effects of prolonged running on Achilles tendon properties were assessed after a 60 min treadmill run and 140 min intermittent shuttle running (simulated cricket batting innings). Before and after exercise, 11 participants performed ramp-up plantar flexions to maximum-voluntary-contraction before gradual relaxation. Muscle-tendon-junction displacement was measured with ultrasonography. Tendon force was estimated using dynamometry and a musculoskeletal model. Gradients of the ramp-up force-displacement curves fitted between 0-40% and 50-90% of the preexercise maximal force determined stiffness in the low- and high-force-range, respectively. Hysteresis was determined using the ramp-up and relaxation force-displacement curves and elastic energy storage from the area under the ramp-up curve. In simulated batting, correlations between tendon properties and shuttle times were also assessed. After both protocols, Achilles tendon force decreased (4% to 5%, P < .050), but there were no changes in stiffness, hysteresis, or elastic energy. In simulated batting, Achilles tendon force and stiffness were both correlated to mean turn and mean sprint times (r = -0.719 to -0.830, P < .050). Neither protocol resulted in fatigue-related changes in tendon properties, but higher tendon stiffness and plantar flexion force were related to faster turn and sprint times, possibly by improving force transmission and control of movement when decelerating and accelerating.

Short report: Recovery of jump performance after a simulated cricket batting innings.

The time-course of physical recovery was determined after a 2-h 20-min, simulated cricket batting innings. Several vertical jump measures were assessed before (baseline), immediately after, 24 h after and 48 h after simulated batting. Six, male, academy cricketers (20 ± 2 years) completed a previously developed simulated batting innings (BATEX) at an outdoor net facility. At each assessment point, participants completed countermovement-jumps, squat-jumps and 5-repeated reactive-jumps on a contact mat. Compared with baseline, countermovement flight time was similar immediately after, but decreased 24 h after batting (-3.0 ± 1.8%, p < 0.05, effect size [ES] ± 90% confidence interval [CI]: -1.38 ± 0.52). At 48 h post, countermovement-jump flight time was similar to baseline. A similar pattern occurred in the squat-jump and the decrease in squat-jump flight time 24 h after simulated batting approached significance (p = 0.053, ES ± CI -0.80 ± 0.51). The 5-repeated reactive-jump measures (flight time, contact time and reactive-strength-index) did not decrease after simulated batting (p > 0.05), but there were moderate effect sizes calculated (0.64-0.96). These findings support the continued use of countermovement flight time to assess recovery in cricket, since full recovery of jump performance occurred 48 h after a simulated, prolonged and high intensity-batting century.

Performance in a simulated cricket batting innings (BATEX): reliability and discrimination between playing standards.

The reliability (test-retest) of running-between-the-wickets times and skill performance was assessed during a batting exercise (BATEX) simulation of 2 h 20 min duration that requires intermittent shuttle running. In addition, performance and physiological responses (heart rate, sweat rate, rating of perceived exertion, blood lactate concentration) were compared between high- and low-grade district club batsmen (n = 22, mean ± s: age 20 ± 2 years, mass 73.4 ± 8.5 kg). Running-between-the-wickets performance was assessed with an infra-red timing system (Swift, Australia) by sampling a 5-m time for the middle section of the straight-line sprints (singles) and the time to complete 5 m in and out of the turn (5-0-5-m turn time). Skill performance was rated as a percentage for good bat-ball contacts. Coefficients of variation for running-between-the-wickets performance and percentage of good bat-ball contacts were both <5%. Percentage of good bat-ball contacts was greater in the high- than low-grade batsmen (70 ± 8 vs. 58 ± 9%, P = 0.01). All other variables were similar between grades. Running-between-the-wickets and skill-performance measures during the BATEX simulation were reliable, thus it can be used in future research.

Movement patterns and physical strain during a novel, simulated cricket batting innings (BATEX).

A simulated cricket batting innings was developed to replicate the physical demands of scoring a century during One-Day International cricket. The simulated innings requires running-between-the-wickets across six 5-over stages, each of 21 min duration. To validate whether the simulated batting innings is reflective of One-Day International batting, movement patterns were collected using a global positioning system (GPS) and compared with previous research. In addition, indicators of physical strain were recorded (heart rate, jump heights, sweat loss, tympanic temperature). Nine club cricketers (mean ± s: age 20 ± 3 years; body mass 79.5 ± 7.9 kg) performed the simulated innings outdoors. There was a moderate trend for distance covered in the simulated innings to be less than that during One-Day batting (2171 ± 157 vs. 2476 ± 631 m · h⁻¹; effect size = 0.78). This difference was largely explained by a strong trend for less distance covered walking in the simulated innings than in One-Day batting (1359 ± 157 vs. 1604 ± 438 m · h⁻¹; effect size = 1.61). However, there was a marked trend for distance covered both striding and sprinting to be greater in the simulated innings than in One-Day batting (effect size > 1.2). Practically, the simulated batting innings may be used for match-realistic physical training and as a research protocol to assess the demands of prolonged, high-intensity cricket batting.

Effects of wearing compression garments on thermoregulation during simulated team sport activity in temperate environmental conditions.

Anecdotal evidence suggests compression garments (CGs) are being worn underneath normal playing attire during team sports. Wearing CGs as a baselayer could possibly increase heat storage, and so this field study investigated the effects of wearing CGs, comprising knee-length shorts and short-sleeved top underneath normal match-day attire (COMP), versus normal match-day attire alone (NORM) on thermoregulation during simulated team sport activity. Ten match-fit field hockey players twice performed 4x15min exercise bouts consisting of repeated cycles of intermittent, varied-intensity 20m shuttle running (Loughborough intermittent shuttle test), once in COMP and once in NORM. Testing was conducted in an indoor gymnasium (ambient conditions: approximately 17 degrees C, approximately 60% relative humidity). Participants acted as their own controls. Heart rate (HR), 15m sprint time, ratings of perceived exertion (RPE), blood lactate concentration, sweat rate and body core temperature (T(core)) were similar between trials (p>0.05). Mean skin temperature (T(skin)) was significantly higher in COMP than NORM (p<0.05). Overall, CGs worn as a baselayer during simulated team sport exercise in temperate ambient conditions had no thermoregulatory benefits nor any detrimental effects on T(core), physiological performance or dehydration. However, the higher T(skin) may affect individual preference for wearing CGs as an undergarment during team sports.

The effect of caffeine ingestion on human neutrophil oxidative burst responses following time-trial cycling.

Following fixed-duration exercise of submaximal intensity, caffeine ingestion is associated with an attenuation of the exercise-induced decline in N-formyl-methionyl-phenyl-alanine (f-MLP) stimulated neutrophil oxidative burst. However, the response following high-intensity exhaustive exercise is unknown. Nine endurance-trained male cyclists ingested 6 mg caffeine or placebo per kilogram of body mass 60 min before cycling for 90 min at 70% of maximal oxygen consumption (VO2max) and then performing a time-trial requiring an energy expenditure equivalent to 30 min cycling at 70% maximum power output. Time-trial performance was 4% faster in the caffeine than in the placebo trial (P = 0.043). Caffeine was associated with an increased plasma adrenaline concentration after 90 min of exercise (P = 0.046) and immediately after the time-trial (P = 0.02). Caffeine was also associated with an increased serum caffeine concentration (P < 0.01) after 90 min of exercise and immediately after the time-trial, as well as 1 h after the time-trial. However, the f-MLP-stimulated neutrophil oxidative burst response fell after exercise in both trials (P = 0.002). There was no effect of caffeine on circulating leukocyte or neutrophil counts, but the lymphocyte count was significantly lower on caffeine (20%) after the time-trial (P = 0.003). Our results suggest that high-intensity exhaustive exercise negates the attenuation of the exercise-induced decrease in neutrophil oxidative burst responses previously observed when caffeine is ingested before exercise of fixed duration and intensity. This may be associated with the greater increase in adrenaline concentration observed in the present study.