Effects of intermittent sprint and plyometric training on endurance running performance

Purpose:The purpose of this study was to compare the effects of intermittent sprint training and plyometric training on endurance running performance.Methods:Fourteen moderately trained male endurance runners were allocated into either the intermittent sprint training group(n = 7)or the plyometric training group(n = 7).The preliminary tests required subjects to perform a treadmill graded exercise test,a countermovement jump test for peak power measurement,and a 10-km time trial.Training included 12 sessions of either intermittent sprint or plyometric training carried out twice per week.On completion of the intervention,post-tests were conducted.Results:Both groups showed significant reduction in weekly training mileage from pre-intervention during the intervention period.There were significant improvements in the 10-km time trial performance and peak power.There was also significant improvement in relative peak power for both groups.The 10-km time trial performance and relative peak power showed a moderate inverse correlation.Conclusion:These findings showed that both intermittent sprint and plyometric training resulted in improved 10-km running performance despite reduction in training mileage.The improvement in running performance was accompanied by an improvement in peak power and showed an inverse relationship with relative peak power.

Comparison of Loaded Countermovement Jump with Different Variable Resistance Intensities on Inducing Post-Activation Potentiation

Purpose The aim of the study was to establish the optimum variable resistance(VR)intensity for loaded countermovement jump(LCMJ)to induce post-activation potentiation(PAP).Methods Eleven male athletes(age 23±2.3 years,height 1.77±0.05 m,body mass 73.7±9.0 kg)attended one familiariza-tion and four testing sessions.Subjects performed their own pre-competition warm up before performing two countermove-ment jumps(CMJ)for baseline measure.Subsequently,they performed 2×3 unloaded(UCMJ)or loaded CMJ(LCMJ)with one of the three VR intensities,Orange(6.7±0.6 kg),Red(14.0±0.9 kg)and Blue(24.0±1.4 kg),in random order,before performing two more CMJ for post-test measure.Each testing session was separated by at least 48 h.Results There was significant increase in jump height in all conditions(P<0.05),but no significant difference in change in jump height between conditions(P>0.05).There were small to moderate effect when comparing Orange and the other conditions.Peak force and velocity increased in Red(P<0.05)and Orange(P<0.05),respectively.Change in jump height was significantly correlated to change in peak velocity(r=0.46,P=0.002)and peak power(r=0.46,P=0.002).Conclusion The findings of the study showed that UCMJ and LCMJ were effective in improving jump height acutely,and an intensity level of about 10%body weight contributed by VR seems to be the optimum resistance level.

Vitamin D Status of Elite Athletes in Singapore and Its Associations With Muscle Function and Bone Health

Purpose The primary aim of this study is to determine the prevalence of vitamin D deficiency and insufficiency among Asian athletes participating in indoor and outdoor sports in equatorial Singapore.Secondary aims are to examine the relationship between vitamin D status and skeletal muscle strength and performance,and bone density.Methods Serum 25(OH)D concentrations were determined in 95 indoor and outdoor athletes across various sports.Skeletal muscle strength and performance were assessed using the isometric mid-thigh pull(IMTP),drop jump test and 30 m sprint test.Bone Mineral Density(BMD)was measured using Dual-energy X-ray Absorptiometry(DXA).Results Mean serum 25(OH)D concentrations were 28.6±8.9 ng/mL among indoor,and 39.2±13.2 ng/mL among outdoor sport athletes respectively(P<0.05).More indoor sport athletes(62%)had insufficient vitamin D compared to outdoor sport athletes(30%)(P<0.05).Outdoor sport athletes exhibited significantly greater peak force generation than indoor sport athletes(2079±470 N vs.1869±546 N,P=0.027).Other markers of muscle function were not significantly different between groups.Indoor and outdoor sport athletes did not have significantly different BMDs although none of the athletes studied presented with poor BMD.Athletes who were deficient in vitamin D had significantly lower BMD compared to athletes with sufficient vitamin D(P=0.01).Conclusion Forty-seven percent of Singaporean athletes studied had suboptimal vitamin D status.Routine monitoring of vitamin D levels among indoor sport athletes should be in place to ensure optimal health and performance.

Effects of Two Isometric Strength Training Methods on Jump and Sprint Performances:A Randomized Controlled Trial

Purpose Isometric strength training (IST) with rapid non-sustained contraction (RIST) is effective in improving the ability to generate force rapidly.However,the neuromuscular adaptation of IST with sustained contraction (SIST) and RIST is not known.Therefore,the aim of the study was to compare the neuromuscular adaptations of RIST with SIST.Methods Thirty-three national floorball players (23.9 ± 3.1 years old;1.69± 0.08 m;64.6± 11.1 kg) were recruited for this study.Pre-and post-test included countermovement jump (CMJ),30-m sprint (TT30),isometric squat at 90° (ISqT90) and 120° (ISqT120) knee angles.They were randomly assigned to either control (Con) (n =9),RIST (n =12) or SIST (n =12)group and performed 12 sessions of intervention training.All groups performed the same sets of exercises,but RIST and SIST had to perform ISqT with and without sustained contraction,respectively.Results Time × group effect for CMJ height (P =0.01,η2p=0.25),peak force (PF) (P =0.03,η2p =0.22) and rate of force development (RFD) (P =0.02,η2p =0.22) obtained from ISqT 120 were noted.A main effect for time was observed in CMJ height,PF obtained from ISqT90 and ISqT120,and RFD obtained from ISqT90 (P < 0.01,0.27 < η2p < 0.57).There was greater improvement in TT30 (P =0.043,d =3.00),ISqT90 PF (P =0.034,d =3.12),ISqT 120 PF (P =0.003,d =4.54) and ISqT120 RFD (P=0.033,d=1.36) in the SIST than the Con group.Conclusion SIST was more effective in improving strength and dynamic performance as compared to RIST,making it a viable training method to enhance dynamic performances.