Preseason changes in markers of lower body fatigue and performance in young professional rugby union players

This study investigated the changes in measures of neuromuscular fatigue and physical performance in young professional rugby union players during a preseason training period. Fourteen young (age: 19.1?±?1.2 years) professional rugby union players participated in the study. Changes in measures of lower body neuromuscular fatigue (countermovement jump (CMJ) mean power, mean force, flight-time) and physical performance (lower body strength, 40?m sprint velocity) were assessed during an 11-week preseason period using magnitude-based inferences. CMJ mean power was likely to very likely decreased during week 2 (?8.1?±?5.5% to ?12.5?±?6.8%), and likely to almost certainly decreased from weeks 5 to 11 (?10?±?4.3% to ?14.7?±?6.9%), while CMJ flight-time demonstrated likely to very likely decreases during weeks 2, and weeks 4–6 (?2.41?±?1% to ?3.3?±?1.3%), and weeks 9–10 (?1.9?±?0.9% to ?2.2?±?1.5%). Despite this, possible improvements in lower body strength (5.8?±?2.7%) and very likely improvements in 40?m velocity (5.5?±?3.6%) were made. Relationships between changes in CMJ metrics and lower body strength or 40?m sprint velocity were trivial or small (<0.22). Increases in lower body strength and 40?m velocity occurred over the course of an 11-week preseason despite the presence of neuromuscular fatigue (as measured by CMJ). The findings of this study question the usefulness of CMJ for monitoring fatigue in the context of strength and sprint velocity development. Future research is needed to ascertain the consequences of negative changes in CMJ in the context of rugby-specific activities to determine the usefulness of this test as a measure of fatigue in this population.     

Effects of low volume isometric leg press complex training at two knee angles on force-angle relationship and rate of force development

This study compared knee angle-specific neuromuscular adaptations after two low-volume isometric leg press complex training programmes performed at different muscle lengths. Fifteen young males were divided into two groups and trained three times per week for 6 weeks. One group (n?=?8) performed 5–7 sets of 3 s maximum isometric leg press exercise, with 4?min recovery, with knee angle at 85°?±?2° (longer muscle-tendon unit length; L-MTU). The other group (n?=?7) performed the same isometric training at a knee angle of 145°?±?2° (180°^?=?full extension; shorter muscle-tendon unit length; S-MTU). During the recovery after each set of isometric exercise, participants performed two CMJ every minute, as a form of complex training. Maximum isometric force (MIF) and rate of force development (RFD) were measured over a wide range of knee angles. Countermovement jump (CMJ) performance and maximum half-squat strength (1RM) were also assessed. Training at S-MTU induced a large increase of MIF (22–58%, p?p?p?=?0.001). In contrast, training at L-MTU, resulted in a moderate and similar (≈12.3%, p?=?0.028) improvement of force at all knee angles. CMJ performance and 1RM were equally increased in both groups after training by 10.4%?±?8.3% and 7.8%?±?4.7% (p?相似文献   

谷氨酰胺对力竭性游泳大鼠心肌组织MDA、GSH含量的影响

目的在于探讨补充外源性谷氨酰胺 (GLN)对力竭性运动大鼠心肌组织中丙二醛 (MDA)和还原型谷胱甘肽(GSH)含量的影响。方法 :采用力竭性游泳运动方式 ,通过补充与不补充GLN对比观察大鼠力竭运动后 18h心肌组织中MDA、GSH含量的变化 ,评价GLN对运动机体心肌组织抗氧能力的影响。结果 :(1)心肌组织MDA含量 ,单纯运动组比安静对照组显著升高 (P <0 .0 1) ,补充GLN运动组心肌MDA含量上升幅度明显低于单纯运动组 ;(2 )心肌组织GSH含量 ,补充GLN安静组高于安静对照组 ,差异显著 (p <0 .0 1) ,补充GLN运动组高于单纯运动组 ,差异显著 (p <0 .0 5 )。结论 :补充外源性GLN有助于提高运动机体心肌组织中的GSH含量 ,增强心肌的抗氧化能力 ,抑制心肌脂质过氧化反应。     

Light-load maximal lifting velocity full squat training program improves important physical and skill characteristics in futsal players

This study aimed to compare the effect of 6 weeks of resistance training or combined resistance training and change of direction exercises on physical performance and motor skills in futsal players. Thirty-four futsal players were divided into full squat group (SG, n = 12), combined full squat and change of direction exercises group (S+CDG, n = 12) and control group (CG, n = 10). The resistance training for SG consisted of full squat with low load (~45–58% 1RM) and low volume (4–6 repetitions), whereas the S+CDG performed the same resistance training program combined with loaded change of direction. Sprint time in 10 and 20 m, change of direction test, countermovement vertical jump (CMJ) height, maximal strength and force–velocity relationship in full squat exercise, kicking speed ball (BS_mean) and repeated sprint ability (RSA_mean) were selected as testing variables. Both experimental groups showed significant improvements for CMJ, BS_mean and all strength parameters. Only SG resulted in significant sprint gains, whereas S+CDG also achieved significant improvements in RSA_mean. The CG remained unchanged after training period. No significant differences were found between both experimental groups. These findings suggest that only 12 sessions of either lightweight resistance training alone, lifting the load at maximal intended velocity or combined with change of direction exercises is enough to improve several physical and skills capacities critical to futsal performance in adult players.     

The acute effects of bodyweight suspension exercise on muscle activation and muscular fatigue

This investigation examined effects of two exercise modes (barbell, BB; bodyweight suspension, BWS) on muscle activation, resistance load, and fatigue. During session one, nine resistance-trained males completed an elbow flexion one-repetition maximum (1RM). During sessions two and three, subjects completed standing biceps curls to fatigue at 70% 1RM utilizing a randomized exercise mode. Surface electromyography (sEMG) recorded muscle activation of the biceps brachii, triceps brachii, anterior deltoid, posterior deltoid, rectus abdominis, and erector spinae. BWS resistance load was measured using a force transducer. Standing maximal voluntary isometric contractions of the elbow flexors recorded at 90° were used to determine the isometric force decrement and rate of fatigue (ROF) during exercise. sEMG and resistance load data were divided into 25% contraction duration bins throughout the concentric phase. BWS resulted in a 67.7?±?7.4% decline in resistance load throughout the concentric phase (p?≤?0.05). As a result, BB elicited higher mean resistance loads (31.4?±?4.0?kg) and biceps brachii sEMG (84.7?±?27.8% maximal voluntary isometric contractions, MVIC) compared with BWS (20.4?±?3.4?kg, 63.4?±?21.6% MVIC). No difference in rectus abdominis or erector spinae sEMG was detected between exercise modes. Isometric force decrement was greater during BWS (?21.7?±?7.0?kg) compared with BB (?14.9?±?4.7?kg); however, BB (?3.0?±?0.8?kg/set) resulted in a steeper decline in ROF compared with BWS (?1.7?±?0.6?kg/set). The variable resistance loading and greater isometric force decrement observed suggest that select BWS exercises may resemble variable resistance exercise more than previously considered.     

Redistributing load using wearable resistance during power clean training improves athletic performance

A popular method to improve athletic performance and lower body power is to train with wearable resistance (WR), for example, weighted vests. However, it is currently unknown what training effect this loading method has on full-body explosive movements such as the power clean. The purpose of this study was to determine what effects WR equivalent to 12% body mass (BM) had on the power clean and countermovement jump (CMJ) performance. Sixteen male subjects (age: 23.2?±?2.7 years; BM: 90.5?±?10.3?kg) were randomly assigned to five weeks of traditional (TR) power clean training or training with 12% BM redistributed from the bar to the body using WR. Variables of interest included pre and post CMJ height, power clean one repetition maximum (1RM), peak ground reaction force, power output (PO), and several bar path kinematic variables across loads at 50%, 70%, and 90% of 1RM. The main findings were that WR training: (1) increased CMJ height (8.7%; ES?=?0.53) and 1RM power clean (4.2%; ES?=?0.2) as compared to the TR group (CMJ height?=??1.4%; 1RM power clean?=?1.8%); (2) increased PO across all 1RM loads (ES?=?0.33–0.62); (3) increased barbell velocity at 90% 1RM (3.5%; ES?=?0.74) as compared to the TR group (?4.3%); and (4) several bar path kinematic variables improved at 70% and 90% 1RM loads. WR power clean training with 12% BM can positively influence power clean ability and CMJ performance, as well as improve technique factors.     

不同强度运动对大鼠十二指肠DMT1、FP1蛋白和肝Hepcidin mRNA表达的影响

目的：研究不同强度游泳运动对大鼠十二指肠DMT1、FP1蛋白及肝hepcidin mRNA表达的影响，探讨运动影响肠铁吸收的调节机制。方法：30只雌性SD大鼠随机分为对照组（control group，CG），适度运动组（moderately exercised group，MG）和过度运动组（strenuously exercised group，SG），每组10只，运动10周后分别取十二指肠和肝。用免疫组织化学的方法测定十二指肠二价金属离子转运体1（divalent metal transporter1，DMT1）和膜铁转运蛋白1（ferroportinl，FPl）的表达，用RT—PCR测定肝hepcidinmRNA的表达。结果：适度运动组DMT1（IRE）和FP1的表达高于对照组（P〈0．05），过度运动组与对照组相比蛋白表达无明显变化；适度运动组肝hepcidin mRNA的表达显著低于对照组（P〈0．05），过度运动组肝hepcidin mRNA的表达与其他两组相比无显著差异。结论：适度运动可能通过hepcidin调节十二指肠DMT1和FP1的表达增强，促进肠铁吸收，满足运动中机体对铁的需求。而过度运动则可能通过大量动用贮存铁满足机体所需，而使肠铁吸收变化不明显。     

Influence of short-term inertial training on swimming performance in young swimmers

The aim of this study was to evaluate the influence of dry-land inertial training (IT) on muscle force, muscle power, and swimming performance. Fourteen young, national-level, competitive swimmers were randomly divided into IT and control (C) groups. The experiment lasted four weeks, during which time both groups underwent their regular swimming training. In addition, the IT group underwent IT using the Inertial Training Measurement System (ITMS) three times per week. The muscle groups involved during the upsweep phase of the arm stroke in front crawl and butterfly stroke were trained. Before and after training, muscle force and power were measured under IT conditions. Simultaneously with the biomechanical measurements on the ITMS, the electrical activity of the triceps brachii was registered. After four weeks of training, a 12.8% increase in the muscle force and 14.2% increase in the muscle power (p?<?.05) were noted in the IT group. Moreover, electromyography amplitude of triceps brachii recorded during strength measurements increased by 22.7% in the IT group. Moreover, swimming velocity in the 100?m butterfly and 50?m freestyle improved significantly following the four weeks of dry-land IT (?1.86% and ?0.76%, respectively). Changes in the C group were trivial. Moreover, values of force and power registered during the ITMS test correlated negatively with the 100?m butterfly and 50?m freestyle swimming times (r value ranged from ?.80 to ?.91). These results suggest that IT can be useful in swimming practice.     

Determinants of countermovement jump performance: a kinetic and kinematic analysis

Abstract

This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump.     

Factors associated with minimal changes in countermovement jump performance throughout a competitive division I collegiate basketball season

ABSTRACT

The purpose of the study was to assess factors that contribute to countermovement jump (CMJ) performance in women’s basketball athletes. Thirteen female athletes participated and were tested for maximal oxygen uptake (VO_2max) and heart rate (HR_max). Athletes were monitored, daily for a total of 21 weeks with heart rate-based wearable devices and CMJ performance and body weight were tested weekly after one day of recovery. 3-jump average height (CMJ_avg), maximum height jump (CMJ_max), and CMJ power (Watts) were calculated and recorded. Playing intensities >85% HR_max, HR_avg, HR_max and training load were averaged for three consecutive days prior to the recovery day. After the season, data was grouped as changes in CMJ power from week one: Large (≤ ?4.39% change), Moderate (?4.4% to ?0.62% change), and Minimal (≥ ?0.61% change) changes. Fixed-effects models revealed a main effect of group (p ≤ 0.05) for CMJ_avg, CMJ_max, VO_2max, weekly percent changes in body weight and for 3-day training load, HR_avg, and playing time at >85% HR_max. When athletes experienced minimal changes in CMJ performance, relative to large changes, they produced greater power, jumped higher, avoided negative changes in weekly body weight, had a greater preseason VO_2max and 3-day average workloads appeared to have an impact on CMJ performance     

Aerobic training alone or combined with strength training affects fitness in elderly: Randomized trial

Abstract

Purpose: To investigate if combined strength and aerobic training can enhance aerobic capacity in the elderly to a similar extent as aerobic training alone when training duration is matched. Methods: Elderly men and women (age 63.2?±?4.7) were randomized into two intervention groups: an aerobic group (AG, n?=?17) and a combined group (CG, n?=?16). Subjects trained 40?minutes three times a week for 12 weeks. Both groups trained 20 minutes at 65% of heart rate reserve on ergometer cycles followed by another 20 minutes on the ergometer cycles for AG and 20-minute strength training for the lower body for CG. The primary outcome was VO₂max. Secondary outcomes were maximal voluntary contraction (MVC) in isometric knee extension, 1 repetition maximum in three leg exercises, body fat, waist-to-hip ratio, blood pressure and score on the Health Survey Short Form 36 (SF-36). Results: Both groups improved VO₂max (p?<?.01) and MVC (p?<?.001). VO₂max increased 17% confidence interval (CI) [7.4–26] in CG and 26% CI [14.1–38.2] in AG, with no significant difference between groups. MVC increased 22% CI [16.3–27.7] in CG and 9% CI [4.6–13.5] in AG with CG improving MVC more than AG (p?<?.01). CG's score on the general health dimension on the SF-36 health survey improved more than AG's score. Conclusion: Elderly can substitute a part of their aerobic training with strength training and still improve VO₂max to a clinically significant degree when strength training is performed with large muscle groups subsequently to the aerobic training. Combined training additionally improves strength and self-assessed general health more than aerobic training alone.     

Validity and reliability of kick count and rate in freestyle using inertial sensor technology

Abstract

In freestyle swimming the arm action is routinely quantified by stroke count and rate, yet no method is currently available for quantifying kick. In this study, we assessed the validity and reliability of inertial sensor technology (gyroscope) to assess kick count and rate. Twelve Paralympic swimmers completed a 100-m freestyle-swimming time-trial and freestyle kicking-only time-trial three times each in a season. An algorithm was developed to detect the up and down beat of individual kicks from the gyroscope trace. For comparative purposes, underwater video analysis provided the criterion measure. The standard error of the estimate (validity) for kick count, expressed as a coefficient of variation, was 5.9% (90% confidence interval 5.5 to 6.4) for swimming, and 0.6% (0.5 to 0.6) for kicking-only trials. The mean bias for kick count was ?1.7% (?2.4 to ?1.1) for swimming, and ?0.1% (?0.2 to ?0.1) for kicking-only trials. Correlations between the sensor and video for kick count were 0.96 (0.95 to 0.97) for swimming, and 1.00 (1.00 to 1.00) for kicking-only trials. The typical error of the measurement (reliability) between trials was approximately 4% for kick count and rate. The inertial sensors and associated software used generated sufficient validity and reliability estimates to quantify moderate to large changes in kick count and rate in freestyle swimming.     

Acute kinematic and kinetic adaptations to wearable resistance during vertical jumping

One variation of vertical jump (VJ) training is resisted or weighted jump training, where wearable resistance (WR) enables jumping to be overloaded in a movement specific manner. A two-way analysis of variance with Bonferroni post hoc contrasts was used to determine the acute changes in VJ performance with differing load magnitudes and load placements. Kinematic and kinetic data were quantified using a force plate and contact mat. Twenty sport active subjects (age: 27.8?±?3.8 years; body mass (BM): 70.2?±?12.2?kg; height: 1.74?±?0.78?m) volunteered to participate in the study. Subjects performed the counter movement jump (CMJ), drop jump (DJ) and pogo jump (PJ) wearing no resistance, 3% or 6% BM affixed to the upper or lower body. The main finding in terms of the landing phase was that the effect of WR was non-significant (P?>?.05) on peak ground reaction force. With regard to the propulsive phase the main findings were that for both the CMJ and DJ, WR resulted in a significant (P?<?.05) decrease in jump height (CMJ: ?12% to ?17%, DJ: ?10% to ?14%); relative peak power (CMJ: ?8% to ?17%, DJ: ?7% to ?10%); and peak velocity (CMJ: ?4% to ?7%, DJ: ?3% to ?8%); while PJ reactive strength index was significantly reduced (?15% to ?21%) with all WR conditions. Consideration should be given to the inclusion of WR in sports where VJ’s are important components as it may provide a novel movement specific training stimulus.

Highlights

• WR of 3 or 6 % BM provided a means to overload the subjects in this study resulting in decreased propulsive power and velocity that lead to a reduced jump height and landing force.

• Specific strength exercises that closely mimic sporting performance are more likely to optimise transference, therefore WR with light loads of 3–6% body mass (BM)appear a suitable tool for movement specific overload training and maximising transference to sporting performance.

• Practitioners can safely load their athletes with upper or lower body WR of 3–6% BM without fear of overloading the athletesover and above the landing forces they are typically accustomed too.

• As a training stimulus it would seem the WR loading provides adequate overload and athletes should focus on velocity of movement to improve power output and jump height i.e. take-off velocity.

     

Creatine kinase,neuromuscular fatigue,and the contact codes of football: A systematic review and meta-analysis of pre- and post-match differences

Physiological or performance tests are routinely utilised to assess athletes’ recovery. At present, the ideal tool to assess recovery remains unknown. Therefore, the aim of this systematic review was to examine the change in creatine kinase (CK) and neuromuscular function as measured via a countermovement jump (CMJ) following a match in the contact codes of football. A comprehensive search of databases was undertaken with RevMan (V 5.3) used for statistical analysis. Our results demonstrated that CK pre- versus post-match (standardised mean difference (SMD)?=?0.90, 95% CI?=?0.50 to 1.31, p?p?p?p?=?.03), and pre- versus 24?h post-match (SMD?=??0.80, 95% CI?=??1.31 to ?0.28, p?=?.002) decreased significantly. There was a significant relationship between the change in CK and the change in CMJ PP from immediately pre to immediately post (r?=??0.924, p?=?.025), and between CMJ immediately following a match and 24?h CK change (r?=??0.983, p?=?.017). In conclusion, CK levels increase and performance in the CMJ decreases following a match of a contact code of football. The identification of this relationship may allow coaching staff to implement a standalone measure of recovery.     

The effects of a single night of complete and partial sleep deprivation on physical and cognitive performance: A Bayesian analysis

ABSTRACT

This study investigated the effects of complete and partial sleep deprivation on multiple aspects of athletic performance. Ten males completed a cognitive function test, maximal handgrip strength, countermovement jump (CMJ) and a 15 min all out cycling test to assess aerobic performance. These tests were performed following 3 different sleep conditions; normal sleep (CON), a 4 hr sleep opportunity (PART) and complete sleep deprivation (DEP). Data were analysed using a Bayesian multi-level regression model to provide probabilities of impairment (p = %). Aerobic performance, CMJ and handgrip strength were impaired by 11.4% (p = 100%), 10.9% (p = 100%) and 6% (p = 97%) following DEP, while aerobic performance and CMJ were highly likely impaired by 4.1% (p = 90%) and 5.2% (p = 94%) following PART. Cognitive reaction time was not impacted by PART or DEP. In contrast the accuracy of responses was highly likely impaired by 2% (91) following DEP, while there was less certainty of impaired accuracy following PART (?1%, p = 73). Multiple aspects of physical and cognitive performance were impacted by sleep deprivation. The greatest detrimental effects were seen for aerobic performance and CMJ. Partial sleep deprivation equating to 4 hrs of sleep causes subtle, but potentially important negative impairments on athletic performance.     

Commercially available compression garments or electrical stimulation do not enhance recovery following a sprint competition in elite cross-country skiers

This study investigated whether commercially available compression garments (COMP) exerting a moderate level of pressure and/or neuromuscular electrical stimulation (NMES) accelerate recovery following a cross-country sprint skiing competition compared with a control group (CON) consisting of active recovery only. Twenty-one senior (12 males, 9 females) and 11 junior (6 males, 5 females) Swedish national team skiers performed an outdoor sprint skiing competition involving four sprints lasting ～3–4 min. Before the competition, skiers were matched by sex and skiing level (senior versus junior) and randomly assigned to COMP (n?=?11), NMES (n?=?11) or CON (n?=?10). Creatine kinase (CK), urea, countermovement jump (CMJ) height, and perceived muscle pain were measured before and 8, 20, 44 and 68?h after competition. Neither COMP nor NMES promoted the recovery of blood biomarkers, CMJ or perceived pain post-competition compared with CON (all P?>?.05). When grouping all 32 participants, urea and perceived muscle pain increased from baseline, peaking at 8?h (standardised mean difference (SMD), [95% confidence intervals (CIs)]): 2.8 [2.3, 3.2]) and 44?h (odds ratio [95% CI]: 3.3 [2.1, 5.1]) post-competition, respectively. Additionally, CMJ was lower than baseline 44 and 68?h post-competition in both males and females (P?相似文献   

TDP提高肌肉力量训练效果的实验研究

为期九周的实验训练结果表明:TDP复合元素板在热激发下发射的特定电磁波用于肌肉力量训练,其最大力量和爆发力的增长率有明显提高,这种有效性与TDP在医用方面的良好生物学效应是相吻合的。而TDP在肌肉内部产生作用的机理,可以在医学领域相应的研究成果中找到一些依据,但更深入细致的研究,尤其是TDP对肌细胞兴奋——收缩内在过程的影响,还需设计新的实验方法以便能在细胞水平上加以探索。     

轻负荷半蹲起下肢力增加速率与各种肌肉收缩运动表现的关系

目的:探讨各种轻负荷条件下半蹲起力-时间曲线特征和力增加速率与各种肌肉收缩运动表现的相关性;分析轻负荷抗阻练习与等长、等动及纵跳动作的下肢发力特征间的内在生物力学联系。方法:募集日本筑波大学9名男子运动员,在测力台上进行不同负荷的半蹲起(Half-squat,HS)以获取地面反作用数据(GRF),进而计算出力增加速率(RFD)。进行最大负荷(>1RM)的静力收缩以测得最大力量(Fmax),进行各种纵跳练习(SJ、CMJ、RJ)以测得跳跃能力参数;采用多关节等速测力系统测取不同角速度下的膝伸展峰力矩(Peak torque,PT);采用Pearson相关系数反映不同负荷半蹲起RFD值与最大力量、跳跃能力和等速膝伸展峰力矩间的相关关系。结果:1)轻负荷半蹲起动作的平均发力时间在0.2 s以内,RFD值在0~60 ms区间内相近或相等;2)20 kg、40 kg和60 kg半蹲起RFD值与Fmax之间无相关关系(P>0.05),60 kg半蹲起RFD值与300°/s条件下的膝伸展PT存在显著性正相关(P<0.01);3)CMJ-JH和RJ-JH显著高于SJ-JH(P<0.01),而RJ的RFD值显著大于SJ和CMJ(P<0.01);4)40 kg半蹲起RFD值与SJ-JH、CMJ-JH之间存在显著性正相关(P<0.05);5)RFD与Fpeak和T-Fpeak之间分别存在显著性正相关和负相关(P<0.05),但Fpeak和T-Fpeak之间未存在相关关系(P>0.05)。结论:轻负荷半蹲起可以作为短跑、游泳等项目运动员起动力量训练手段,以减少起跑和起跳入水的反应时,强化起点技术;在20~60 kg负荷范围内,RFD值在短时间内保持相对恒定;轻负荷半蹲起在保持高输出功率的同时,具有更加高速的发力特征,可作为提高优秀运动员纵跳能力的有效练习手段。     

Traditional balance and slackline training are associated with task-specific adaptations as assessed with sensorimotor tests

The purpose of this study was to measure alterations in sensorimotor skills and balance resulting from slackline training and conventional balance training. Forty-three physically fit subjects were randomized into three groups. Two groups practiced three times a week for 15?minutes, including at least once supervised session, on the slackline or perform conventional balance training for 6 weeks. The control group was not allowed to perform any balance training. Before and after the intervention, the subjects underwent sensorimotor and strength tests. The results of our intra-class correlation analysis showed that the stability parameters from the multifunctional training device (MFT, 0.7), the height during the countermovement jump (CMJ, 0.95) and the maximum force (0.88) during leg press showed excellent reliability. A post hoc comparison indicated a larger effect of conventional training (almost 11% reduction in MFT stability) compared with slackline training in group-wide comparisons of the pre- to the post-training measurements. The factor analysis showed that stability and sensorimotor assessment using MFT were correlated, as were height during CMJ and maximal force during leg press, which represented dynamic strength. Because CMJ had the highest intra-class correlation value, it was chosen over maximum force from leg press. For these reasons, only two out of nine measured parameters, namely MFT stability and CMJ, were analysed across groups. The only observed difference between the two groups was MFT stability (slackline???1.5%, conventional???13%), whereas the improvement of CMJ was the same (slackline?+?3%, conventional?+?3%). It can be concluded that slacklining is partly complementary to conventional sensorimotor training.     

Swimming

Abstract

The effect on drag of a Speedo Fast‐skin suit compared to a conventional suit was studied in 13 subjects (6 males, 7 females) swimming at different velocities between 1.0 and 2.0 m?s^‐1. The active drag force was directly measured during front crawl swimming using a system of underwater push‐off pads instrumented with a force transducer (MAD system). For a range of swimming speeds (1.1, 1.3, 1.5 and 1.7 m?s^‐1), drag values were estimated. On a group level, a statistically non‐significant drag reduction effect of 2% was observed for the Fast‐skin suit (p = 0.31). Therefore, the 7.5% reduction in drag claimed by the swimwear manufacturer was not corroborated.