Ethical standards in sport and exercise science research: 2014 update·

Sensory Stimulation of the Triceps Surae Muscle Complex Modulates Spinal Reflex Responses-A Comparison between Tapotement Massage and Repetitive Peripheral Magnetic Stimulation (rPMS)

BACKGROUND

The reduction of muscular hypertonia is important in the treatment of various diseases or rehabilitation. This study aims to test the efficacy of a 5 Hz mechanical muscle stimulation (tapotement massage) in comparison to a 5 Hz repetitive peripheral magnetic stimulation (rPMS) on the neuromuscular reflex response.

METHODS

In a randomized control trial, 15 healthy volunteers were administered with either 5 Hz rPMS, tapotement massage, or rPMS sham stimulation. The posterior tibial nerve was stimulated with rPMS and sham stimulation. The Achilles tendon was exposed to a mechanically applied high-amplitude 5 Hz repetitive tendon tapotement massage (rTTM). The tendon reflex (TR) was measured for the spinal response of the soleus muscle.

RESULTS

After rPMS, there was a reduction of the TR response (-9.8%, p ≤ 0.034) with no significant changes after sham stimulation. Likewise, TR decreased significantly (-17.4%, p ≤ 0.002) after Achilles tendon tapotement intervention.

CONCLUSIONS

These findings support the hypothesis that both afferent 5 Hz sensory stimulations contributed to a modulation within the spinal and/or supraspinal circuits, which resulted in a reduction of the spinal reflex excitability. The effects could be beneficial for patients with muscle hypertonia and could improve the functional results of rehabilitation programs.

Role of resistance training in bone macro and micro damages in an estrogen absence animal model

AIMS

We evaluated the effects of resistance training (RT) on bone properties, morphology, and bone extracellular matrix (ECM) remodeling markers in an ovariectomy (OVX) rat model.

MAIN METHODS

Thirty-six female rats were divided into four groups: sham sedentary, OVX sedentary, sham RT, and OVX RT. Rats performed RT for ten weeks, during which they climbed a ladder with progressive loads attached to the tail. Tibias were stored for dual-energy X-ray densitometry (DXA), micro-computed tomography (micro-CT), and biomechanical, biophysical, and biochemical analysis. Femurs were stored for morphological, gene expression, and gelatin zymography analysis.

KEY FINDINGS

OVX decreased bone mineral density, stiffness, maximal load, and calcium content, which was reversed by RT. The trabecular number, connectivity, and MMP-13 gene expression decreased in OVX groups. Furthermore, OVX increased run-related transcription factor-2 (RUNX-2) and osteoprotegerin (OPG) gene expression, and increased the number of adipocytes in bone marrow and MMP-2 activity.

SIGNIFICANCE

RT was efficient in preventing or reversing changes in bone biomechanical properties in OVX groups, improving fracture load and resilience, which is relevant to prevent fractures. On the other hand, RT did not decrease the number of bone adipocytes in the OVX-RT group. However, RT was efficient for increasing trabecular thickness and cortical bone volume, which improved bone resistance. Our findings provide further insights into the mechanisms involved in the role of RT in OVX damage protection.

Higher Playing Times Accumulated Across Entire Games and Prior to Intense Passages Reduce the Peak Demands Reached by Elite, Junior, Male Basketball Players

The aim of this study was to analyze the effects of different factors on the external peak demands (PD) encountered by elite, junior, male basketball players in games, including the (1) total playing time during games and (2) playing time accumulated directly prior to each PD episode. Workload variables included the PD for total distance, distance covered in different intensity zones, accelerations >2 m·s-2 (ACC), decelerations <-2 m·s-2 (DEC), and PlayerLoad. PD were calculated across different sample durations for each variable. Linear mixed models were used to identify differences in PD between groups based on playing times. PD for total distance (5-min window), high-speed running (>18 km·h-1) distance (2-min window), and ACC (30-s, 45-s, 1-min, 2-min, and 5-min windows) were significantly (p < .05) higher for players who completed lower total playing times (16.6 ± 2.4 min) than players who completed higher total playing times (25.0 ± 3.4 min). The PD for total distance (30-s, 45-s, 1-min, and 2-min windows), high-speed running distance (30-s and 5-min windows), and PlayerLoad (1-min and 2-min windows) were significantly (p < .05) higher for players who accumulated lower playing times before each PD episode than players who accumulated higher playing times before each PD episode. Players who undertake less playing time overall and prior to each PD episode can reach higher peak external loads aggregated across varied time windows. These findings can inform tactical coaching decisions during games for high external loads to be accomplished during important passages of play.

Comparing Different Filter-Parameter for Pre-Processing of Brain-Stimulation Evoked Motor Potentials

Background: Brain stimulation motor-evoked potentials (MEPs) are transient signals and not periodic signals, and thus, they differ significantly in their properties from classical surface electromyograms. Unsuitable pre-processing of MEPs due to inappropriate filter settings leads to distortions. Filtering of extensor carpi radialis MEPs with transient signal characteristics of 20 subjects was examined. The effects of a 1st-order Butterworth high-pass filter (HPF) with different cut-off frequencies 1 Hz, 20 Hz, 40 Hz, and 80 Hz and a 5 Hz Butterworth high-pass filter with degrees 1st, 2nd, 4th, 8th-order are investigated for the filter output. Results: The filtering of the MEPs with an inappropriate filter setting led to distortions on the parameters peak-to-peak amplitudes of the MEP (MEP_pp) and the absolute integral of the MEP (MEP_area). The lowest distortions of all of the examined filter parameters were revealed after filtering with the lowest filter order and the lowest cut-off frequency. The 1st-order 1 Hz HPF calculation results in a difference of −0.53% (p < 0.001) for the MEPpp and −1.94% (p < 0.001) for the MEParea. Significance: Reproducibility is a major concern in science, including brain stimulation research. Only the filtering of the MEPs with appropriate filter settings led to mostly undistorted MEPs.

Knee strength measurement: Can we switch between isokinetic dynamometers?

BACKGROUND: Isokinetic evaluation is considered the gold standard in muscle strength measurement due to its sensitivity, intra-dynamometer reproducibility and usefulness in the injury prevention screening and follow up of subjects with musculoskeletal pathologies, neurological disease or after surgical operation. However, can one switch among different isokinetic dynamometers for the purpose of knee muscles evaluation? OBJECTIVES: To comprehensively evaluate the compatibility of the isokinetic short concentric and eccentric strength evaluation protocol and of the fatigability resistance evaluation between three different isokinetic devices. METHODS: Eighteen recreationally active men underwent three isokinetic knee testing sessions on three different isokinetic devices with 7–10 days of rest between each session. Relative (Pearson’s r product-moment correlation coefficient – PCC) and absolute (standard error of measurement – SEM, Cohen effect sizes (d) and probabilistic inferences – MBI) parameters of reproducibility were determined to assess the inter-dynamometer agreement. RESULTS: For the short concentric and eccentric strength evaluation protocol, the extensors in concentric mode and the flexors in eccentric mode can be compared (eventually with transposition formulas provided) between Biodex, Con-Trex and Cybex (almost all PCC ⩾ 0.80). The DCR could be compared between Con-Trex and Cybex and between Biodex and Cybex pairs (eventually with transposition formula provided). For the fatigability resistance evaluation protocol, the total sum can be compared for extensors (eventually with transposition formulas provided) for PM for all dynamometer pairs considered and, in the case of MW, only for Biodex and Con-Trex (PCC ⩾ 0.80). CONCLUSIONS: Only some of the parameters derived either from the short concentric and eccentric strength evaluation protocol or the fatigability resistance evaluation protocol may be interchangeable providing transposition formulas are applied. Otherwise, isokinetic findings are largely system-dependent save some specific instances.

Specific Absolute Velocity Thresholds during Male Basketball Games Using Local Positional System; Differences between Age Categories

The aim of this study was (I) to establish absolute specific velocity thresholds during basketball games using local positional system (LPS) and (II) to compare the speed profiles between various levels of competitions. The variables recorded were total distance (TD); meters per minute (m·min); real time (min); maximum speed (Km h−1), distance (m), percentage distance, and percentage duration invested in four speed zones (standing–walking; jogging; running; and high-speed running). Mean and standard deviation (±SD) were calculated, and a separate one-way analysis of variance was undertaken to identify differences between competitions. TD (3188.84 ± 808.37 m) is covered by standing–walking (43.51%), jogging (36.58%), running (14.68%), and sprinting (5.23%) activities. Overall, 75.22% of the time is invested standing–walking, jogging (18.43%), running (4.77%), and sprinting (1.89%). M·min (large effect size), % duration zone 2 (moderate effect size); distance zone 4 (large effect size), and % distance zone 4 (very large effect size) are significantly higher during junior than senior. However, % distance zone 1 (large effect size) and % duration zone 1 (large effect size) were largely higher during senior competition. The findings of this study reveal that most of the distance and play time is spent during walking and standing activities. In addition, the proportion of time spent at elevated intensities is higher during junior than in senior competition.

Face Cooling During Swimming Training in Tropical Condition

The aim of this study was to test the effect of face cooling with cold water (1.2 ± 0.7^°C) vs. face cooling with neutral water (28.0 ± 3.0^°C) during high-intensity swimming training on both the core temperature (T_co) and thermal perceptions in internationally ranked long-distance swimmers (5 men’s and 3 women’s) during 2 randomized swimming sessions. After a standardized warm-up of 1,200 m, the athletes performed a standardized training session that consisted of 2,000 m (5 × 400 m; start every 5’15”) at a best velocity then 600 m of aerobic work. Heart rate (HR) was continuously monitored during 5 × 400 m, whereas T_co, thermal comfort (TC), and thermal sensation (TS) were measured before and after each 400 m. Before and after each 400 m, the swimmers were asked to flow 200 mL of cold water (1.2^°C) or neutral (22^°C) water packaged in standardized bottles on their face. The swimmers were asked don’t drink during exercise. The velocity was significantly different between cold water and neutral water (p < 0.004 – 71.58 m.min^–1 ± 2.32 and 70.52 m.min^–1 ± 1.73, respectively). The T_co was increased by ±0.5^°C at race pace, under both face cooling conditions with no significant difference. No significant changes were noted in mean HR (i.e., 115 ± 9 and 114 ± 15 bpm for NW and CW, respectively). TC was higher with Cold Cooling than Neutral Cooling and TS was lower with Cold cooling compared with Neutral cooling. The changes in perceptual parameters caused by face cooling with cold water reflect the psychological impact on the physical parameters. The mean velocity was less important with face cooling whereas the heat rate and T_co were the same in the both conditions. The mechanism leading to these results seems to involve brain integration of signals from physiological and psychological sources.

The Influence of Playing Formation on Physical Demands and Technical-Tactical Actions According to Playing Positions in an Elite Soccer Team

The aim of this study was to examine the differences in the physical demands and technical-tactical actions encountered by soccer players between two playing formations (1-4-2-3-1 and 1-4-4-2) for each playing position. Twenty-three professional male soccer players who played 31 official matches participated in this study. Players were classified according to their playing position: central defenders (CD), wide defenders (WD), central midfielders (CM), wide midfielders (WM), offensive midfielders (OM) and forwards (FW). The physical demands were collected as total distance (TD), distance covered in different speed thresholds, and number of accelerations and decelerations. Also, the technical-tactical variables were recorded. The results showed that the 1-4-2-3-1 playing formation demanded decelerations between 2–4 m·s² (p = 0.027; ES = 0.26) in comparison with 1-4-4-2 for all players. Likewise, forwards (FW) and central midfielders (CM) registered higher physical demands playing with the 1-4-2-3-1 compared to the 1-4-4-2 formation. Regarding the technical-tactical actions, they showed differences between the playing positions of the two playing formations. The findings suggest coaches prescribe specific training programs based on the influence of the playing formation and playing position on the physical demands and technical-tactical actions encountered by players during official match-play.

Acute Effects of Ballistic vs. Passive Static Stretching Involved in a Prematch Warm-up on Vertical Jump and Linear Sprint Performance in Soccer Players

ABSTRACT

López Mariscal, S, Sánchez Garcia, V, Fernández-García, JC, and Sáez de Villarreal, E. Acute effects of ballistic vs. passive static stretching involved in a prematch warm-up on vertical jump and linear sprint performance in soccer players. J Strength Cond Res 35(1): 147-153, 2021-The purpose of this study was to compare the effects of introducing passive static and ballistic stretching in a standard soccer match warm-up. The variables addressed were the counter movement jump (CMJ), Abalakov jump, and the 40-m linear sprint. The sample was composed of 33 male subjects, divided into 2 age groups. U16 and adult players formed the groups, to cross check whether there were differences between them. Each group was further subdivided into 2 groups regarding the type of stretching carried out during the stretching phase. Before the warm-up, the tests previously described were assessed. In the experimental phase, standard stretching was carried out, consisting of an initial phase in which players had to execute continuous running; a general phase in which players had to make articulate moves; a technical phase in which players had to execute exercises with the ball; a 5 vs. 5 small-sided game was carried out during the tactical phase; and in the final phase, activation exercises and sprints were carried out by the players. Eventually, the same variables were assessed again once the warm-up was finished. There were no statistically significant differences between the 2 types of stretching included in the prematch warm-up. It can be concluded that ballistic and passive static stretching (<10 seconds) did not cause, under these circumstances, any effect in the assessed variables related to soccer performance (linear sprint, CMJ, and Abalakov). This has to be considered by coaches when devising soccer-related warm-ups.

NeuroHeal Improves Muscle Regeneration after Injury

Musculoskeletal injuries represent a challenging medical problem. Although the skeletal muscle is able to regenerate and recover after injury, the process engaged with conservative therapy can be inefficient, leading to a high re-injury rate. In addition, the formation of scar tissue implies an alteration of mechanical properties in muscle. There is still a need for new treatments of the injured muscle. NeuroHeal may be one option. Published studies demonstrated that it reduces muscle atrophy due to denervation and disuse. The main objective of the present work was to assess the potential of NeuroHeal to improve muscle regeneration after traumatic injury. Secondary objectives included characterizing the effect of NeuroHeal treatment on satellite cell biology. We used a rat model of sport-induced injury in the gastrocnemius and analyzed the effects of NeuroHeal on functional recovery by means of electrophysiology and tetanic force analysis. These studies were accompanied by immunohistochemistry of the injured muscle to analyze fibrosis, satellite cell state, and fiber type. In addition, we used an in vitro model to determine the effect of NeuroHeal on myoblast biology and partially decipher its mechanism of action. The results showed that NeuroHeal treatment advanced muscle fiber recovery after injury in a preclinical model of muscle injury, and significantly reduced the formation of scar tissue. In vitro, we observed that NeuroHeal accelerated the formation of myotubes. The results pave the way for novel therapeutic avenues for muscle/tendinous disorders.

Relative Weights of Physical Strength Factors in Sports Events: Focused on Similarity Sports Events Group According to the Sports Physiological View

The purpose of this study was to investigate the relative weights of physical strength factors in sports events. We selected 16,645 people as a sample group who participated in physical fitness measurements through eight sports science centers across the country from 2016 until August of 2018, and divided into four sports types depending on the sports physiological view: type A: short-term muscular power and short-term muscular endurance, type B: mid-term muscular power, type C: long-term cardiorespiratory endurance, type D: coordination capability (CC), agility, flexibility, and balance. Categorized the performance level into excellent athletes and non-excellent athletes, and standardized (T-score) the measured value after considering sex, age and sports type group. Used logistic regression analysis for the method of analysis, and calculated the relative weights of physical strength factor with different sports by using Wald value which was calculated from logistic regression analysis. As a result, the relative weights of physical factor in type A were power 30%, muscular power (MP) 18%, CC 16%, agility 11%, flexibility 10%, cardiorespiratory endurance (CE) 1%, and balance 0%. The relative weights of physical factor in type B were muscular endurance (ME) 43%, MP 25%, power 20%, balance 9%, CE 2%, flexibility 1%, agility 0%, and CC 0%. The relative weights of physical factor in type C were ME 41%, CE 37%, power 10%, agility 8%, flexibility 2%, CC 2%, ME 0%, and balance 0%. Need more specific classification standard for type D sports. Hope the results of this study were used to measure physical fitness level and used as baseline data for recruiting future talents.

Injury Profile of Elite Male Young Soccer Players in a Spanish Professional Soccer Club: A Prospective Study During 4 Consecutive Seasons

Context: As the number of injuries in young soccer players increases, an epidemiological study is the first step in improving preventive strategies. Objectives: To analyze the injury profile of a Spanish professional soccer club’s academy during 4 consecutive seasons and to examine the injury incidence across different chronological age groups. Design: Prospective cohort design. Setting: Aggregate injury and exposure data collected during 4 consecutive seasons. Participants: Three hundred nine elite male young soccer players. Main Outcomes Measures: Injuries that led to participation time missed from training and match play prospectively reported by medical or coaching staff of the club. Results: A total of 464 time-loss injuries were observed during this study period. The overall injury incidence was 2.93 injuries per 1000 hours, with higher incidence during matches than during training (10.16 vs 2.10 injuries/1000 h; rate ratio [RR] = 0.21; 95% confidence interval [CI], 0.17–0.25; P < .05), with the U14 age group presenting the lowest injury rate (2.39 injuries/1000 h; RR = 1.15–1.57; P < .05). In terms of injury severity, moderate injuries were the most frequent (1.42 injuries/1000 h). Muscle injuries were the most common type of injuries (57.7%; 2.75 injuries/1000 h; RR = 1.84–13.4; P < .05), and hamstrings (93/268) were the most affected muscle group (0.58 injuries/1000 h; RR = 1.58–2.91; P < .05). Injury incidence showed a seasonal variation as indicated by peaks in August and October. In matches, specifically, the match period between 75 and 90 minutes showed the highest injury incidence (10.29 injuries/1000 h; RR = 1.89–6.38; P < .01). Conclusions: The findings of this study suggest that specific preventive strategies must be implemented to try to reduce the injury incidence in Spanish elite young soccer players attending to the characteristics of each age group.

Acute kinematics and kinetics changes to wearable resistance during change of direction among soccer players

This study determined the acute changes in kinematics and kinetics when an additional load equivalent to 5% body mass was attached to the torso during change of direction (COD). In this within-subject repeated measures study, 14 male soccer players (age: 18.29 ± 0.32 years) volunteered to participate. Subjects performed COD under two conditions in randomized order: (1) no WR, and (2) with WR. No significant differences between the loaded and unloaded conditions in actual COD angle, approach speed, braking time, propulsive time, contact time, COD completion time (all p > 0.05, ES = 0.05-0.11), and all measured kinematic parameters (all p > 0.05, ES = 0-0.18). Nonetheless, ankle plantar/dorsi flexion ROM had possibly small increase in the loaded condition (ES = 0.24). Kinetics analysis has shown that the loaded condition was likely to have small increase in relative peak vertical propulsive ground reaction force (GRF, p = 0.11, ES = 0.41), and possible small increases in relative peak braking GRF (vertical: p = 0.21, ES = 0.42; total: p = 0.22, ES = 0.38), relative peak total propulsive GRF (p = 0.24, ES = 0.26), and relative braking impulse (horizontal, vertical, and total; p = 0.27-0.41, ES = 0.26-0.28). WR did not significantly change the acute movement techniques, meanwhile induced small increases in important kinetic stimuli for potential adaptation in COD.

Leg asymmetry and muscle function recovery after anterior cruciate ligament reconstruction in elite athletes: a pilot study on slower recovery of the dominant leg

The aim of this study was to examine performance in hopping tests in male athletes after anterior cruciate ligament reconstruction (ACLR) in the 4-to-6 months post-surgery period. A total of 36 athletes (24 ACLR and 12 controls) participated in this study. The ACLR group consisted of athletes who had undergone an ACLR on their dominant side (ACL DG n=16) or non-dominant side (ACL NDG n=8). Participants completed the following functional tests: a single-leg hop (SLH), single-leg triple hop (SL3H) and single-leg counter movement jump (SLCMJ), then the limb symmetry index (LSI) was calculated. There were no significant differences between the dominant and the non-dominant legs for all functional tests when comparing the ACL DG and the ACL NDG at 6 months after surgery. At 6 months after ACLR, the LSI of the two legs was within acceptable values, whether the athlete had the operation on their dominant or non-dominant leg (except the mean LSI for the ACL DG in the SLCMJ test). Furthermore, the control group showed higher performances as compared to the ACL group for all variables at 6 months after surgery, despite acceptable LSI. We concluded that an early return to “full participation to training” is not recommended in participants who have undergone an ACLR with patellar tendon grafts.

Peak Match Demands in Young Basketball Players: Approach and Applications

Background: The aim of this study is to describe the peak match demands and compare them with average demands in basketball players, from an external load point of view, using different time windows. Another objective is to determine whether there are differences between positions and to provide an approach for practical applications. Methods: During this observational study, each player wore a micro technology device. We collected data from 12 male basketball players (mean ± SD: age 17.56 ± 0.67 years, height 196.17 ± 6.71 cm, body mass 90.83 ± 11.16 kg) during eight games. We analyzed intervals for different time windows using rolling averages (ROLL) to determine the peak match demands for Player Load. A separate one-way analysis of variance (ANOVA) was used to identify statistically significant differences between playing positions across different intense periods. Results: Separate one-way ANOVAs revealed statistically significant differences between 1 min, 5 min, 10 min, and full game periods for Player Load, F (3,168) = 231.80, η_p² = 0.76, large, p < 0.001. It is worth noting that guards produced a statistically significantly higher Player Load in 5 min (p < 0.01, η_p² = −0.69, moderate), 10 min (p < 0.001, η_p² = −0.90, moderate), and full game (p < 0.001, η_p² = −0.96, moderate) periods than forwards. Conclusions: The main finding is that there are significant differences between the most intense moments of a game and the average demands. This means that understanding game demands using averages drastically underestimates the peak demands of the game. This approach helps coaches and fitness coaches to prepare athletes for the most demanding periods of the game and present potential practical applications that could be implemented during training and rehabilitation sessions.

Sex differences in competitive surfers' generic and specific strength capacity

To compare the pop-up and counter movement jump (CMJ) and to analyse the relationships among the variables between sexes and different ages [under (U16), over (O16) 16 years] in male and female competitive surfers. Eighty-three surfers were divided according to sex, male (n = 55) and female (n = 28), and to age, U16 (n = 47) and O16 (n = 36). Vertical jump and pop-up movements were measured through the vertical ground reaction force with a force plate. CMJ demonstrated that the O16 male group exhibited significantly greater force compared to females in the concentric phase of the jump (CMJ_FMAX) (p < 0.01, ES = 1.82, large). Female U16 and O16 groups presented increased unloading rates in the eccentric phase compared to male surfers (CMJ_ULR) (p < 0.05, ES = 0.73, moderate and p < 0.05, ES = 0.12, trivial, respectively). O16 males obtained significantly greater values than O16 females in the push-up phase (POP_PUSH) (p < 0.05, ES = 0.76, moderate). Moderate correlations were found between lower-body power capacity and the pop-up (r = 0.32; ± 0.16 CL, p < 0.01, 98.1/1.9/0, very likely, moderate). General and skill-specific strengths are different in competitive male and female surfers, dependent upon their age range. The moderate association between CMJ and pop-up suggests that the pop-up might be influenced by other factors such as coordination or upper-body strength. Therefore, competitive surfers should also train the upper body strength and overall coordination in order to improve the performance of the pop-up movement.

Utilizing Video-Based Trainings to Improve Decision Making in High School Quarterbacks

Despite the role of working memory capacity (WMC) in decision making, there is a dearth of empirical literature concerned with working memory and how it relates to tactical decision making in sport. The temporal occlusion paradigm has often been used by sport researchers to improve tactical decision making and, thus, provides a well-established foundation for creating decision-making trainings. Therefore, the purpose of the current study was to explore the implementation of computer-based learning modules to improve the tactical decision making of four high school quarterbacks with varying levels of WMC, utilizing a single-subject, multiple baseline design. The learning modules utilized a temporal occlusion paradigm and present a novel intervention aimed at improving decision making in quarterbacks. Data were analyzed using visual analysis and improvement rate difference (IRD). Overall, results did not demonstrate a causal relationship between changes in accuracy of decision making after implementation of the learning modules but did provide moderate evidence for improvement in reaction time for decision making due to the learning modules. The learning modules were met with positive perceptions from the four participants, and the participant with the lowest WMC showed evidence of improvement in both accuracy and speed of decision making. Limitations as well as implications will be discussed.

Eccentric versus Concentric - Which Is the Most Stressful Cardiovascularly and Metabolically?

The purpose of this study was to compare the fatigability resistance profile and the physiological responses of strenuous concentric (CON) versus eccentric (ECC) isokinetic exercises. At two different sessions, 12 healthy sedentary male subjects (24.3 ± 2.5 years) performed strenuous CON and ECC isokinetic exercises. The protocol consisted of three sets of 12 maximal repetitions, separated by 30-s intervals, at a velocity of 60°·s for both flexor and extensor knee muscles of the dominant leg. Metabolic (ventilation, oxygen uptake, blood lactate concentration) and cardiovascular (HR, mean arterial blood pressure) parameters were registered before, throughout, and after the isokinetic session. The isokinetic data analysis revealed a more pronounced fatigue in the hamstrings than in the quadriceps in the ECC mode (fatigue index, ratio between the third and the first sets, of 94.8% ± 11.8% vs 86.4% ± 10.8%; P < 0.05). All physiological responses studied increased gradually during the isokinetic evaluation, both in CON and ECC modes. For total work normalized by physiological responses, cardiovascular and metabolic variables were lower in the CON than in the ECC mode, a sign of a weaker efficiency in CON mode (ratio between performance and physiological cost). In conclusion, the study shows a specific fatigability resistance profile consisting of an early decrease of ECC hamstring performance compared with the quadriceps profile. In addition, we confirm that physiological consequences are important during strenuous isokinetic exercises but ECC exercise produces less stress on the cardiovascular and the metabolic systems than does CON exercise.

Taping Benefits Ankle Joint Landing Kinematics in Subjects With Chronic Ankle Instability

Context: Although taping has been proven effective in reducing ankle sprain events in individuals with chronic ankle instability, insight into the precise working mechanism remains limited. Objectives: To evaluate whether the use of taping changes ankle joint kinematics during a sagittal and frontal plane landing task in subjects with chronic ankle instability. Design: Repeated measure design. Setting: Laboratory setting. Participants: A total of 28 participants with chronic ankle instability performed a forward and side jump landing task in a nontaped and taped condition. The taping procedure consisted of a double “figure of 6” and a medial heel lock. Main Outcome Measures: 3D ankle joint kinematics was registered. Statistical parametric mapping was used to assess taping effect on mean ankle joint angles and angular velocity over the landing phase. Results: For both the forward and side jump, a less plantar flexed and a less inverted position of the ankle joint were found in the preparatory phase till around touchdown (TD) in the taped condition (P < .05). In addition, for both jump landing protocols, a decreased dorsiflexion angular velocity was found after TD (P < .05). During the side jump protocol, a brief period of increased inversion angular velocity was registered after TD (P < .05). Conclusions: Taping is capable of altering ankle joint kinematics prior to TD, placing the ankle joint in a less vulnerable position at TD.

[Influence of overweight and obesity on strength in childhood]

Introduction

Introduction: overweight and obesity reach a high prevalence since childhood in Spain. Objective: to describe the effect of overweight and obesity, in schoolchildren of eleven years of age, in tests that assess the strength of both the lower and upper extremities, as well as speed. Method: four hundred and twenty-three schoolchildren of eleven years of age participated in the study. Basic anthropometric characteristics were obtained and several tests of the EUROFIT battery were developed. Results: normal-weight boys and girls had better scores in physical condition tests in general. Therefore, the vertical and horizontal jumps, bar suspension and abdominals were higher in the participants with normal-weight (p < 0.05). In addition, they performed in less time a speed circuit in both sexes (p < 0.001); however, in relation to the manual isometric strength, in the group of girls those who are overweight or obese have better results (p < 0.01). Conclusions: overweight and obese children of eleven year-olds showed a lower muscular performance, except in the case of manual isometric strength. Several equations haven been also determined for predicting the results of physical tests carried out such as jumps, dynamometry and speed, through sex and body mass index (BMI).

Neurodynamic sliders promote flexibility in tight hamstring syndrome

ABSTRACT Hamstring injury prevention puts emphasis on optimizing the muscle's strength-length relationship. To assure appropriate muscle length, flexibility training is imperative. As neurodynamics play an important role herein, the goal of this study was to explore the intervention effect of home-based neurodynamic slider program on hamstring flexibility. Fifty physically active male subjects were randomly assigned to either performing a neurodynamic sliding technique (3 × 20 reps) or a static stretching protocol (3 × 30″) on a daily basis for a 6-week period. Hamstring flexibility was assessed by means of the Straight Leg Raise at baseline, immediately after the intervention and after 4 weeks follow up. There was no between group baseline difference in hamstring flexibility. The repeated measure ANOVA showed a significant interaction effect for group × time (p < 0.001). Independent sample t-test showed a significantly higher increase in flexibility gain in the neurodynamic group immediately after the intervention (p < 0.001), as well as at 4 weeks retention analysis (p = 0.001) compared to the static stretch group. In conclusion, neurodynamic sliders might be more efficient than regular static stretching in affecting hamstring flexibility in the long run.

Repetitive Peripheral Magnetic Nerve Stimulation (rPMS) as Adjuvant Therapy Reduces Skeletal Muscle Reflex Activity

Background: The reduction of muscle hypertonia and spasticity, as well as an increase in mobility, is an essential prerequisite for the amelioration of physiotherapeutical treatments. Repetitive peripheral magnetic nerve stimulation (rPMS) is a putative adjuvant therapy that improves the mobility of patients, but the underlying mechanism is not entirely clear.

Methods: Thirty-eight participants underwent either an rPMS treatment (N = 19) with a 5 Hz stimulation protocol in the posterior tibial nerve or sham stimulation (N = 19). The stimulation took place over 5 min. The study was conducted in a pre-test post-test design with matched groups. Outcome measures were taken at the baseline and after following intervention.

Results: The primary outcome was a significant reduction of the reflex activity of the soleus muscle, triggered by a computer-aided tendon-reflex impact. The pre-post differences of the tendon reflex response activity were −23.7% (P < 0.001) for the treatment group. No significant effects showed in the sham stimulation group.

Conclusion: Low-frequency magnetic stimulation (5 Hz rPMS) shows a substantial reduction of the tendon reflex amplitude. It seems to be an effective procedure to reduce muscular stiffness, increase mobility, and thus, makes the therapeutic effect of neuro-rehabilitation more effective. For this reason, the 5 Hz rPMS treatment might have the potential to be used as an adjuvant therapy in the rehabilitation of gait and posture control in patients suffering from limited mobility due to spasticity. The effect observed in this study should be investigated conjoined with the presented method in patients with impaired mobility due to spasticity.

Running Performance and Position is Not Related to Decision-Making Accuracy in Referees

We aimed to assess if running performance is related to decision-making accuracy in referees. We also investigated the relationships between movement, position, decision-making and time of infringement. The study included 347 free kicks and penalties awarded during all 15 home field matches for one team in the Norwegian top league. Movement and position were measured by a radio-based positioning system, and two external experts analysed the video clips. The referees made the correct decision in 98% of the assessed foul situations. There were no associations between the correctness and running speed at the time of the infringements or total distance accumulated during the 30 s prior to the infringement (p>0.08). Decision-making accuracy was not associated with the referees’ position in relation to the infringements (p=0.82) or the area where the infringements occurred (p=0.28). Most foul play incidents were sanctioned in the central area of the field (84%) where the distance to the infringements was shorter (13.4 m, 95% CI 12.8–14.0) than in the lateral areas (21.9 m, 95% CI 20.4–23.4). Norwegian top referees were practically always right when they interfered, possess the necessary fitness to avoid fatigue that would influence decision-making accuracy, and maintain adequate positional ability throughout the matches.

Influence of acute high-intensity exercise on salivary nitric oxide levels

This study, employing an exercise versus control crossover design, was conducted to investigate the influence of acute high-intensity exercise on salivary nitric oxide (NO) levels. Nine healthy males (aged 23.8 ± 1.4 years) performed ergometer exercise at 80%VO_2peak for 60 min, whereas controls sat at rest for 60 min. Saliva samples were collected before (Pre: 0800 h) and after (Post 0-h: 0900 h, Post 1-h: 1000 h, Post 2-h: 1100 h, Post 3-h: 1200 h) the interventions. Salivary NO levels were determined by colorimetric assay. It was found that the salivary NO levels in controls were decreased (P < 0.05) at Post 0-h (-94 ± 15), Post 1-h (-80 ± 20), Post 2-h (-92 ± 34) and Post 3-h (-145 ± 39) relative to the Pre values. Under exercise conditions, salivary NO levels did not change after high-intensity ergometer exercise relative to the Pre values. Thus, the response of salivary NO levels appeared to differ between high-intensity ergometer exercise and inactivity, that exercise-related stress induces the production of salivary NO.

Energetic Demands of Interchange and Full-Match Rugby League Players

Cummins, CJ, Gray, AJ, Shorter, KA, Halaki, M, and Orr, R. Energetic demands of interchange and full-match rugby league players. J Strength Cond Res 32(12): 3456-3464, 2018-The purpose of this study was to describe and compare the metabolic demands of rugby league for interchange and full-match players in relation to positional groups. Eighteen elite rugby league players were recruited. A time-motion model was used to estimate the energy expenditure and metabolic demands of rugby league match-play using Global Positioning System (GPS) technology. This approach uses players' GPS velocity-time curves to examine running velocity. Players were categorized into positional groups (outside backs, adjustables, wide-running, and hit-up forwards) and then further categorized into full-match or interchange players. Compared with their full-match counterparts, interchange wide-running forwards expended greater energy (43.1 ± 6.1 vs. 28.6 ± 7.5 kJ·kg, p ≤ 0.001, effect size [ES] = -2.38) and produced a higher anaerobic index (p = 0.016, ES = 0.56) and mean power (7.4%, p = 0.003, ES = 0.66) per match. Full-match adjustables expended 94.8% more energy (p ≤ 0.001, ES = -2.3) and performed more moderate accelerations (10.1%, p = 0.014, ES = -0.57) and decelerations (7.6%, p = 0.017, ES = -0.8), than their interchange counterparts. Outside backs did not interchange and hit-up forwards rarely (n = 2) played an entire match. Differing metabolic demands were identified for interchange and full-match players across positional groups, suggesting position-specific conditioning drills are required to model the energetic demands of match-play.

Prolonged sitting increases the risk of gallstone disease regardless of physical activity: a cohort study

OBJECTIVES

We aimed to examine the relationship between sitting time and the development of ultrasonography-diagnosed gallstone disease (GSD) in young and middle-aged Korean men and women.

MATERIAL AND METHODS

We conducted a cohort study of 147,237 participants without GSD at baseline who underwent a health checkup examination between 2011 and 2015 and were followed annually or biennially until December 2016. Sitting time and physical activity were measured using the validated Korean version of the international physical activity questionnaire short form. GSD was defined as either having had a cholecystectomy or having gallstones based on ultrasound.

RESULTS

During 486,376 person-years of follow-up, 2382 incident GSD cases were identified. Both prolonged sitting time and inactive physical activity had a significant independent association with the increased risk of GSD. The multivariate-adjusted hazard ratios (95% confidence interval for GSD comparing sitting times of 5-9 and ≥10 h/day with the sitting time of <5 h/day were 1.08 (0.97-1.21) and 1.15 (1.02-1.29), respectively (p for trend = .023). The multivariate-adjusted hazard ratios (95% CIs) for GSD in both the inactive and the minimally active groups compared with HEPA group were 1.22 (1.08-1.38) and 1.13 (0.99-1.28, respectively (p for trend = .001).

CONCLUSION

This study demonstrated that sitting time may be associated with GSD risk regardless of physical activity. The findings of this study suggest that both increasing participation in physical activity and reducing sitting time may be independently important in reducing the risk of GSD.

Scoring Strategies Differentiating between Winning and Losing Teams during FIBA EuroBasket Women 2017

This study aimed to examine the scoring strategies differentiating between winning and losing teams during FIBA EuroBasket Women 2017 in relation to different game scores. Data were gathered for all games of FIBA EuroBasket Women 2017 from the official website. The investigated scoring strategies were fast break points (FBP); points in the paint (PP); points from turnover (PT); second chance points (SCP); and points from the bench (PB). Games were classified with cluster analysis based on their score difference as close, balanced, and unbalanced and the differences in the scoring strategies between winning and losing teams were assessed using magnitude-based statistics. Results revealed no substantial differences in FBP in any investigated cluster. Furthermore, winning teams showed a substantially higher number of PP and PT (in close and unbalanced games) and SCP (in balanced and unbalanced games) compared to losing teams. Finally, winning teams scored substantially lower and higher number of BPs in close games and unbalanced games, respectively, compared to losing teams. In conclusion, all the investigated scoring strategies discriminate between winning and losing teams in elite women’s basketball except for FBP. These results provide useful information for basketball coaches to optimize their training sessions and game strategies.

Reliability, Validity, and Sensitivity of a Novel Smartphone-Based Eccentric Hamstring Strength Test in Professional Football Players

PURPOSE

To evaluate the test-retest reliability, sensitivity, and concurrent validity of a smartphone-based method for assessing eccentric hamstring strength among male professional football players.

METHODS

A total of 25 healthy male professional football players performed the Chinese University of Hong Kong (CUHK) Nordic break-point test, hamstring fatigue protocol, and isokinetic hamstring strength test. The CUHK Nordic break-point test is based on a Nordic hamstring exercise. The Nordic break-point angle was defined as the maximum point where the participant could no longer support the weight of his body against gravity. The criterion for the sensitivity test was the presprinting and postsprinting difference of the Nordic break-point angle with a hamstring fatigue protocol. The hamstring fatigue protocol consists of 12 repetitions of the 30-m sprint with 30-s recoveries between sprints. Hamstring peak torque of the isokinetic hamstring strength test was used as the criterion for validity.

RESULTS

A high test-retest reliability (intraclass correlation coefficient = .94; 95% confidence interval, .82-.98) was found in the Nordic break-point angle measurements. The Nordic break-point angle significantly correlated with isokinetic hamstring peak torques at eccentric action of 30°/s (r = .88, r² = .77, P < .001). The minimal detectable difference was 8.03°. The sensitivity of the measure was good enough that a significance difference (effect size = 0.70, P < .001) was found between presprinting and postsprinting values.

CONCLUSION

The CUHK Nordic break-point test is a simple, portable, quick smartphone-based method to provide reliable and accurate eccentric hamstring strength measures among male professional football players.

The Effects of Cryotherapy on Knee Joint Position Sense and Force Production Sense in Healthy Individuals

The proprioceptive information received from mechanoreceptors is potentially responsible for controlling the joint position and force differentiation. However, it is unknown whether cryotherapy influences this complex mechanism. Previously reported results are not universally conclusive and sometimes even contradictory. The main objective of this study was to investigate the impact of local cryotherapy on knee joint position sense (JPS) and force production sense (FPS). The study group consisted of 55 healthy participants (age: 21 ± 2 years, body height: 171.2 ± 9 cm, body mass: 63.3 ± 12 kg, BMI: 21.5 ± 2.6). Local cooling was achieved with the use of gel-packs cooled to -2 ± 2.5°C and applied simultaneously over the knee joint and the quadriceps femoris muscle for 20 minutes. JPS and FPS were evaluated using the Biodex System 4 Pro apparatus. Repeated measures analysis of variance (ANOVA) did not show any statistically significant changes of the JPS and FPS under application of cryotherapy for all analyzed variables: the JPS’s absolute error (p = 0.976), its relative error (p = 0.295), and its variable error (p = 0.489); the FPS’s absolute error (p = 0.688), its relative error (p = 0.193), and its variable error (p = 0.123). The results indicate that local cooling does not affect proprioceptive acuity of the healthy knee joint. They also suggest that local limited cooling before physical activity at low velocity did not present health or injury risk in this particular study group.

Impact of Official Matches on Soccer Referees' Power Performance

The evaluation of match officials’ neuromuscular performance is now an important consideration and the vertical jump test is considered suitable for assessing lower limb power, partly because it is directly related to refereeing. The aim of this study, therefore, was to determine the effect of soccer matches on match officials’ vertical jump performance by assessing various biomechanical variables. Eighteen field referees (FRs) and 36 assistant referees (ARs) who officiated in 18 official matches participated in this study. Before the match, at half time and immediately after the match, officials performed two countermovement jumps. Flight phase time (FT), maximum force production (MFpropulsion), time to production of maximum force (TMFpropulsion), production of maximum power (MP), maximum landing force (MFlanding) and time to stabilization (TTS) were calculated for all jumps. There was a tendency for match officials’ jumping performance to improve after matches than beforehand (FR: effect size (ES) = 0.19 ± 0.36, possibly trivial; AR: ES = 0.07 ± 0.17, likely trivial). There were also likely small and very likely moderate differences between FRs’ MP in pre-match and half-time jumps (ES = 0.46 ± 0.47) and in their pre- and post-match jumps (ES = 0.71 ± 0.48). These results indicate that refereeing soccer matches does not reduce vertical jump performance; the subsequent neuromuscular fatigue is not sufficient to affect landing technique.

Differences in Physical Performance According to the Competitive Level in Amateur Handball Players

Estibaliz, R, Fabio, N, Rodrigo, RC, Daniel, C, Josune, RN, and Javier Y. Differences in physical performance according to the competitive level in amateur handball players. J Strength Cond Res 34(7): 2048-2054, 2020-The aim of this study was to compare physical performance in amateur handball players of 2 different competitive levels. Thirty-four senior handball players were divided into 2 groups according to their competitive level (regional category: REG or national category: NAC). Although no significant differences were found between groups in any of the horizontal jump (HJ) or vertical jump (VJ) variables (p > 0.05), NAC players obtained a better performance in the repeated sprint ability (RSA) test (RSABest [the best attempt] and RSATT [the total time in the total of sprints] in 15 m and 30 m), in change of direction ability (CODA) and in the Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) test (p < 0.01, effect size = -1.32 to 1.75, large). A significant association was observed between the body mass index (BMI) and the HJ or VJ capacity (r = -0.35 to -0.55, p < 0.01), the RSA15mBest and RSA30mBest (r = 0.41 to 0.59, p < 0.01), and YYIR1 distance (r = -0.54, p ≤ 0.05), and a also between the performance in the HJ or the VJ and the RSA15mBest and RSA30mBest, the CODA and the YYIR1, and between the RSA30mBest and the YYIR1 (r = -0.54, p ≤ 0.05). Specific strength and conditioning programs should aim toward improving RSA, CODA, and YYIR1, as these abilities may be needed at higher levels of competition. The programs also should aim toward improved HJ and VJ abilities, given their association with RSA, CODA, and YYIR1 performance. Moreover, maintaining an adequate BMI may aid players to sustain greater physical performance levels.

Maximal Strength Training as a Therapeutic Approach in Long-Standing Anorexia Nervosa: A Case Study of a Woman With Osteopenia, Menstrual Dysfunction, and Compulsive Exercise

In persons with anorexia nervosa (AN), compulsive exercise and osteopenia are common symptoms. Although treatment of osteopenia besides weight regain is lacking, maximal strength training (MST) has been found to be effective in other populations. Such training has not been prescribed to those with AN due to uncertainty of tolerance. We therefore examined use of MST in a woman with long-standing AN, osteopenia, menstrual dysfunction, and compulsive exercise. The MST intervention consisted of four exercises: three sets of five repetitions maximum (RM), 3 times per week for 16 weeks. We examined muscle strength, bone mineral density (BMD), AN psychopathology, and compulsive exercise at baseline, posttest, and 6-month follow-up. Attendance rate was 100%. The subject improved muscle strength by 20% to 40%. BMD in lumbar spine improved by 4% to posttest, and by 8% from baseline to 6-month follow-up. The BMD T-scores shifted from values classified as osteopenic to normal values throughout the course of the intervention, despite continuance of menstrual dysfunction and lack of weight gain. No changes in AN psychopathology or levels of compulsive exercise were detected. Perceived psychological benefits including new bodily experiences were self-reported by the subject, emphasizing the importance of close follow-up by competent instructors.

Effect of eccentric action velocity on expression of genes related to myostatin signaling pathway in human skeletal muscle

The aim of this study was to investigate the effects of an acute bout of eccentric actions, performed at fast velocity (210º^.s^-1) and at slow velocity (20º^.s^-1), on the gene expression of regulatory components of the myostatin (MSTN) signalling pathway. Participants performed an acute bout of eccentric actions at either a slow or a fast velocity. Muscle biopsy samples were taken before, immediately after, and 2 h after the exercise bout. The gene expression of the components of the MSTN pathway was assessed by real-time PCR. No change was observed in MSTN, ACTRIIB, GASP-1 or FOXO-3a gene expression after either slow or fast eccentric actions (p > 0.05). However, the MSTN inhibitors follistatin (FST), FST-like-3 (FSTL3) and SMAD-7 were significantly increased 2 h after both eccentric actions (p < 0.05). No significant difference between bouts was found before, immediately after, or 2 h after the eccentric actions (slow and fast velocities, p > 0.05). The current findings indicate that a bout of eccentric actions activates the expression of MSTN inhibitors. However, no difference was observed in MSTN inhibitors’ gene expression when comparing slow and fast eccentric actions. It is possible that the greater time under tension induced by slow eccentric (SE) actions might compensate the effect of the greater velocity of fast eccentric (FE) actions. Additional studies are required to address the effect of eccentric action (EA) velocities on the pathways related to muscle hypertrophy.

Investigating the game-related statistics and tactical profile in NCAA division I men's basketball games

The aim of this study was to analyze the game-related statistics and tactical profile in winning and losing teams in NCAA division I men’s basketball games. Twenty NCAA division I men’s basketball close (score difference: 1-9 points) games were analyzed during the 2013/14 season. For each game, the game-related statistics were collected from the official teams’ box scores. Number of ball possessions, offensive and defensive ratings and the Four Factors (effective field goal percentage; offensive rebounding percentage, recovered balls per ball possession, free throw rate) were also calculated. The tactical parameters evaluated were: ball reversal, dribble in key area, post entry, on-ball screen, off-ball screen, and hand off. Differences between winning and losing teams were calculated using a magnitude-based approach. Winning teams showed a likely higher percentage of 3-point goals made, number of defensive rebounds and steals and a very likely higher number of free throws made and free throws attempted. Furthermore, winning teams showed a likely higher team offensive rating and effective field goal percentage and a very likely higher free throw rate compared to losing teams. Finally, the results revealed a likely higher number of ball reversals and post entries in winning teams compared to losing teams. This study highlighted the game-related statistics and the tactical actions differentiating between winning and losing teams in NCAA Division I men’s basketball close games. Coaches should use these results to optimize their training sessions, focusing on those variables that might increase the possibility to win close games.

Officiating Role Influences the Physical Match Activity Profiles of Rugby League Touch Judges and Referees

This study investigated the effect of the officiating role on physical activity profiles of rugby league match officials during match-play. Physical performance indicators were collated from 23 match officials, resulting in 78 observations. Match officials were categorised into two groups: referees and touch judges. Microtechnology facilitated the quantification of total distance (m), relative distance (m⋅min^-1), maximum velocity (m⋅s^-1), the percentage of high intensity running distance (% total > 3.01 m⋅s^-1), walking distance (<1 m⋅s^-1), jogging distance (1.01 – 3 m⋅s^-1), fast jogging distance (3.01 - 5 m⋅s^-1), and sprinting distance (>5 m⋅s-1). Multivariate analysis modelled the main effect of the officiating role with follow up univariate analyses identifying significant differences. A significant effect was noted (V = 750; F(8, 66) = 24.71; p < 0.05) with referees covering a greater total distance (7767 ± 585 vs. 7022 ± 759 m), relative distance (90 ± 6 vs. 82 ± 8 m⋅min^-1), jogging distance (3772 ± 752 vs. 3110 ± 553 m), and fast jogging distance (2565 ± 631 vs. 1816 ± 440 m) compared to touch judges. Touch judges covered greater distances while sprinting (1012 ± 385 vs. 654 ± 241 m). Results provide important guidance in the development of training programs for match officials.

Competition Load Described by Objective and Subjective Methods During a Surfing Championship

Fernández-Gamboa, I, Yanci, J, Granados, C, Freemyer, B, and Cámara, J. Competition load described by objective and subjective methods during a surfing championship. J Strength Cond Res 32(5): 1329-1335, 2018-The aims of this study were to describe the competition load of surfers during a single heat through objective and subjective methods and to analyze the relationship between objective and subjective methods with the judges' score. Ten competitive surfers were fitted with a global positioning system (GPS) during a competitive heat. The GPS was synchronized with a chronometer and a stationary video camera to identify the surfer's specific actions. After the end of each heat, participants were assessed for the rating of perceived respiratory and muscular exertion (RPEres, RPEmus), and also, official scores from every participant were collected. A very large significant relationship between wave-riding distance and respiratory perceived exertion heat load (RPEres HL, r = 0.79; ±0.26 confidence limit [CL], p < 0.01, 99.5/0.4/0.1, very likely) was found. Active time was also very large and significantly related to both RPEres HL (r = 0.75; ±0.29 CL, p < 0.05, 99.0/0.8/0.2, very likely) and muscular perceived exertion heat load (RPEmus HL, r = 0.83; ±0.22 CL, p < 0.01, 99.8/0.2/0.0, most likely). Very large significant correlation was obtained between the RPEres and score (r = 0.83; ±0.22 CL, p < 0.01, 99.8/0.2/0.0, most likely). The subjective method seems to be a good instrument to assess the HL of a surf competition. Wave characteristics seem to be an important factor in perceived exertion during competitive surfing.

The reliability and validity of a video-based method for assessing hamstring strength in football players

Background/Objective

Evaluating hamstring strength by isokinetic dynamometry is limited by various practical issues such as time and cost. A video-based Nordic hamstring exercise is introduced as an alternative option. The aims of this study are to evaluate 1.) the between-session reliability and 2.) concurrent validity of the testing method compared to a standardized isokinetic dynamometry.

Methods

Thirty male elite footballers were recruited for the study. From the Nordic hamstring exercise, the video-analysis-determined Nordic break-point angles where the participant could no longer withstand the force of the fall (eccentric mode) and the number of seconds that the player could hold at 30° forward flexion angle (isometric mode) were measured. Intra-class correlation coefficients for between-session reliability, Pearson r correlations between the current method and isokinetic dynamometry were calculated.

Results

The reliability of the eccentric mode was moderate (ICC _(2,1) = 0.82) while that of isometric mode was poor (ICC _(2,1) = 0.57). The Nordic break-point angle of the eccentric mode significantly correlated with the concentric and eccentric hamstring peak torque (r = 0.48 and 0.58, p < 0.001), while the isometric was not (r = 0.02 - 0.07, p > 0.05).

Conclusion

The eccentric mode of the video-based hamstring strength test was a moderately reliable and valid method to measure the eccentric hamstring strength in elite football players.

Technical Alterations during an Incremental Field Test in Elite Male Tennis Players

PURPOSE

We investigated technical and physiological responses along with their relationships during an incremental field test to exhaustion specific to tennis (TEST) in elite players.

METHODS

Twenty male elite tennis players completed TEST, which consisted of hitting alternatively forehand and backhand strokes at increasing ball frequency (ball machine) every minute. Ball accuracy (BA), ball velocity (BV), and tennis performance (TP) index (TP = BA × BV) were determined by radar and video analysis for each stroke, in addition to cardiorespiratory responses and blood lactate concentrations.

RESULTS

At low intensities (less than 80% of maximal oxygen uptake [V˙O2max]), technical performance was steady. From 80% to 100% of V˙O2max, significant and steady decreases in BV (-9.0% and -13.3%; P = 0.02 and P = 0.002), BA (-19.4% and -18.4%; both P < 0.001), and TP (-27.4% and -29.15%; both P = 0.002) occurred for forehands and backhands, respectively. Changes in TP and blood lactate concentration from 60% to 100% of V˙O2max were inversely correlated (r = -0.51, P = 0.008). BV was 5.2% higher (P = 0.042) for forehand versus backhand, and there was no difference between strokes for both BA (P = 0.930) and TP (P = 0.536).

CONCLUSION

Technical alterations (i.e., decrease in BV, BA, and TP) in elite players undergoing TEST only occurred at high intensity (>80% of V˙O2max), presumably because of the use of compensatory strategies to overcome fatigue. Above this intensity, all technical indices decreased steadily until exhaustion, independently of the stroke nature.

Relation between serum myokines and phase II cardiac rehabilitation

Patients with coronary heart disease or acute myocardial infarction after cardiac catheterization with stenting referred for phase II cardiac rehabilitation (CR) were grouped according to their preference. Cardio-pulmonary exercise testing (CPET) was used to determine oxygen uptake ((Equation is included in full-text article.)) at peak exercise and anaerobic threshold (AT). The control patients received counseling only while the experiment group received 36 sessions of CR in 3 to 6 months. Exercise physiology parameters and serum myokines (myostatin, insulin-like growth factor-1 (IGF-1), and interleukin-6 (IL-6) were measured pre- and postrehabilitation.There were 29 patients in the experiment group and 10 in the control group, with no significant differences in baseline parameters. The experiment group had prominent progress in aerobic capacity and body composition after CR, but their serum myokine concentrations did not change significantly. Serum myostatin is positively correlated to peak (Equation is included in full-text article.)pre- and post-training, and pretraining AT (Equation is included in full-text article.), after adjusting for age, sex, and body composition. Serum IGF-1 is positively correlated with grip strength before training.Serum myostatin level is positively correlated to aerobic capacity, and IGF-1 level is positively correlated to grip strength in cardiac patients receiving CR.

The Validation of a Paddle Power Meter for Slalom Kayaking

The ability to quantify power within the sport of slalom kayaking would provide coaches and athletes objective data to monitor performance. This study determined the validity of a kayak paddle power meter and subsequent relationship between work rate and stroke kinetics. One participant completed multiple trials of a flat-water, straight-line sprint and a sequence of slalom gates at numerous intensities to attain the velocity:power relationship. Laboratory results identified the kayak paddles’ strain gauges were valid and reliable, and field tests presented a cubic relationship for power as a function of velocity in the straight-line sprint (R ² =0.982) and the slalom-specific test (R ² =0.993). Further analysis of stroke kinetics identified velocity of hand movement at individual peak force capability to be critical in the highest work rates achieved for both slalom and flat-water sprinting. It was concluded that the kayak paddle power meter tested is a valid means of recording work rate and stroke kinetics during kayaking in the field.

A Forefoot Strike Requires the Highest Forces Applied to the Foot Among Foot Strike Patterns

Ground reaction force is often used to predict the potential risk of injuries but may not coincide with the forces applied to commonly injured regions of the foot. This study examined the forces applied to the foot, and the associated moment arms made by three foot strike patterns. 10 male runners ran barefoot along a runway at 3.3 m/s using forefoot, midfoot, and rearfoot strikes. The Achilles tendon and ground reaction force moment arms represented the shortest distance between the ankle joint axis and the line of action of each force. The Achilles tendon and joint reaction forces were calculated by solving equations of foot motion. The Achilles tendon and joint reaction forces were greatest for the forefoot strike (2 194 and 3 137 N), followed by the midfoot strike (1 929 and 2 853 N), and the rearfoot strike (1 526 and 2 394 N). The ground reaction force moment arm was greater for the forefoot strike than for the other foot strikes, and was greater for the midfoot strike than for the rearfoot strike. Meanwhile, there were no differences in the Achilles tendon moment arm among all foot strikes. These differences were attributed mainly to differences in the ground reaction force moment arm among the three foot strike patterns.

Fractionated Concurrent Exercise throughout the Day Does Not Promote Acute Blood Pressure Benefits in Hypertensive Middle-aged Women

Hypertension is a chronic disease that affects about 30% of the world’s population, and the physical exercise plays an important role on its non-pharmacological treatment. Anywise, the dose–response of physical exercise fractionation throughout the day demands more investigation, allowing new exercise prescription possibilities. Therefore, this study aimed to analyze the acute blood pressure (BP) kinetics after 1 h of exercises and the BP reactivity after different concurrent exercise (CE) sessions and its fractioning of hypertensive middle-aged women. In this way, 11 hypertensive women voluntarily underwent three experimental sessions and one control day [control session (CS)]. In the morning session (MS) and night session (NS), the exercise was fully realized in the morning and evening, respectively. For the fractionized session (FS), 50% of the volume was applied in the morning and the remaining 50% during the evening. The MS provided the greatest moments (p ≤ 0.05) of post-exercise hypotension (PEH) for systolic BP (SBP) and highest reduction of BP reactivity for SBP (~44%) and diastolic BP (DBP) (~59%) compared to CS (p ≤ 0.05). The findings of the present study have shown that MS is effective for PEH to SBP, as well as it promotes high quality of attenuation for BP reactivity, greater than the other sessions.

The effects of block training on pacing during 20-km cycling time trial

The aim of this study was to determine the effects of block training (BL) on pacing during a 20-km hilly cycling time trial (TT) in trained cyclists. Twenty male cyclists were separated into 2 groups: control and BL. The training of each cyclist was monitored during a period of 3 weeks. In the first week cyclists performed an overload period of 7 consecutive days of high-intensity interval training followed by 2 weeks of normal training. Cyclists performed 1 TT before intervention and 2 TT after 7 and 14 days at the end of training. Each training session consisted of 10 sets of 3 repeated maximal-effort sprints (15, 30, and 45 s) with an effort/recovery duration ratio of 1:5. The main finding of this study was that the power output displayed a significantly higher start from the start until the halfway point of the TT (p < 0.05). Additionally, power output was characterized by a significant higher end spurt in the final 2 km in the BL after 2 weeks at the end of training (p < 0.05). In addition, after 2 weeks at the end of the overload period the distribution of cadence was significantly lower throughout the TT (p < 0.01). Therefore, a short period of consecutive days of intense training enhances cycling performance and changes the power output in the beginning and final part of the TT in trained cyclists.