Background: Literature has shown a growing number of published studies on Patellofemoral Pain Syndrome every year.The increasing evidence base has revealed a significant number of reviews which makes it confusing for clinicians and researchers to choose from the best evidence.This study aimed to gather the reviews on Patellofemoral Pain Syndrome and provide information about the most common clinical tests, risk factors, exercise treatment and outcome measures.In addition, secondary questions aimed to report the study settings and patient characteristics of the primary included studies.Methods: Studies eligible for this Review of Reviews were those published from 1993 to July 2013.Databases searched included PubMed, CINAHL, SPORTDiscus, Pedro and the Cochrane Library.Four key areas were searched using the words: PFPS, Anterior Knee Pain (AKP) or Chondromalacia patella (CP), plus a keyword.The keywords for the four research topics were a) risk factors; b) exercise treatment; c) diagnostic clinical tests and d) psychometric outcome measurements.Only reviews with clear methodological strategy were included.A two-stage evaluation was performed in each review assessment.At first, the level of evidence was graded and then the methodological quality of each review was assessed.Results: Full text screening revealed that only 18 reviews were eligible for use.The selected reviews included 213 primary studies.After excluding duplicates, 144 primary studies were screened to answer the secondary questions.A gold standard clinical test for PFPS assessment cannot be reached and the use of functional tasks should be considered.The quadriceps strength deficits are still the only evidence based risk factors along with the dynamic malalignment of the lower limb.More research is still required on strength and flexibility deficits of other lower limb muscles.The quadriceps-based exercises are still the only ones to have strong evidence together with hamstrings, quadriceps, gastrocnemius and anterior hip muscles stretching.Finally, the usage of Activities of Daily Living Scale is recommended as the best outcome measure. Conclusion:There is no evidence on whether the above treatment and assessment methods should be used in sedentary people or differently across population groups or gender.More RCTs with large populations, powered correctly, in clinical environments are called for in further research.
Purpose: Ischemic preconditioning (IPC) has been used to protect myocardial cells against ischemiareperfusion injury and is recently utilized for improving exercise performance.It is unknown whether remote IPC (RIPC) to tissues not involved in exercise can induce similar exercise improvements and what "dose" of IPC is necessary to induce exercise performance benefits.This study determined if unilateral and bilateral upper limb RIPC improves lower body anaerobic power output.Methods: Using two randomized, sham-controlled, crossover study designs, we studied 43 recreationally-active adults.For study 1, unilateral RIPC was used, while for study 2, the ischemic stimuli was increased to bilateral occlusion.After either the RIPC or sham control treatment, subjects completed four 30 s Wingate anaerobic tests on a Monark cycle ergometer with 2 min passive rest between trials. Results:In the unilateral occlusion trial, peak power, mean power, and fatigue index were not different between the two conditions at every Wingate test.In the bilateral occlusion trial, mean power was greater in the RIPC condition during the first Wingate test compared with the sham control (both p<0.05).Additionally, peak power was elevated following the RIPC condition versus the sham control for the final Wingate test (p<0.05). Conclusion:Remote ischemic preconditioning applied bilaterally increased lower body power output over a series of Wingate anaerobic tests.Unilateral RIPC, however, had no effect on any of the performance variables, suggesting that there is a threshold for the amount of target tissues needed to elicit anaerobic performance benefits.
Objectives: To further quantify the characteristics of cold-water swimmers, and to examine the potential exercise benefits, weight changes, perceptions of cold tolerance, and safety concerns related to swimming recreationally in cold water.Methods: After 3 months (December 21 -March 21) of swimming regularly in cold water in the San Francisco Bay (water temperature range: 9.6° C (49.3° F) to 12.6° C (54.7° F)), 103 subjects (76 men, 27 women) underwent a detailed biophysical analysis (weight, body mass index, and % body fat (circumference method)).Swimmers also completed a questionnaire that included questions related to background, exercise patterns, safety, and cold tolerance.To allow for before-and-after comparisons, a sub-group of 50 subjects had biophysical measurements both before, and again after the 3-month winter swim period.Results: Swimmers were typically in a middle-aged category (mean: 54.3±10.8;range: 24-79, years), employed full-time (69.9%), had a recreational swim background (62.1%), and had body mass index (BMI) (25.9±3.6 kg/m 2 ) and % body fat (23.8±7.5 %) values that were consistent with average American values.The exercise time per week of the subjects (mean: 131.3± 50.8 minutes/week; median: 120 minutes/week) was significantly greater than an intermediate-intensity value of 100 minutes/week based on American College of Sports Medicine /American Heart Association (ACSM/AHA) recommendations (P<0.001).Although 27 of 50 before-and-after subjects lost weight (mean weight loss: 2.1 ±2.6 kg; range of weight loss: 0.1-10.8kg), subjects overall did not significantly gain or lose weight, or change BMI or % fat (P>0.1 for all before-and-after comparisons).The most frequently reported safety concerns were marine life (47.4%)and cold/hypothermia (46.4%), followed by boats (30.9%), currents (19.6%), cramps/fatigue (15.5%), and other (14.4%).A report of feeling more adversely affected by cold was associated with a lower BMI (Coef.= -2.81;P= 0.002), lower % fat (Coef.= -6.66;P<0.001), and less time in the water per swim (Coef.= -4.23;P= 0.029), while a report of feeling less affected by cold was associated with a higher BMI (Coef.= 2.55; P= 0.001), higher % fat (Coef.= 3.83; P= 0.010), and more time in the water per swim (Coef.= 3.51; P= 0.039).Conclusions: Individuals with a wide variety of ages, body types, and backgrounds are able to swim recreationally in cold water.Such swimmers typically are not obese and exceed the ACSM/AHA recommendations for weekly exercise.Marine life and cold/hypothermia are frequent safety concerns; our results suggest that swimmers who report worse cold tolerance are more likely to be leaner and limit time in the water, while those who report better cold tolerance are more likely to have a higher % body fat and spend more time in the water per swim.
Objective: To compare the angles of both hemibodies and movements associated with sporting gestures in road cyclists.Methods: Fifteen right-handed male road cyclists, with a mean age of 27 ± 4.25 years, participated in the study.Subjects who were younger than 18 years old or were previously diagnosed with posture impairment, motor disorders, and cognitive or mental deficits were excluded.Measurement procedures were performed using biophotogrammetry and kinemetry to analyze the angles and biomechanics of sporting gestures during the activities.Results: Based on the results of biophotogrammetry, the angles measured showed symmetry among the participants.The kinematics analysis revealed that the trunk flexion did not show any significant differences between the angles when the sporting gestures were performed.When the triple maximum flexion of the lower limbs and the maximum extension of the lower limbs were analyzed, a statistical significance (p < 0.05) between the angles in both sitting and standing positions was found.However, the results showed a direct association with the desired physiological movement, which did not affect the function. Conclusion:The results showed that the biomechanics of the angles between both hemibodies and the sporting gestures in cyclists were not affected.This finding is directed in particular to the implementation and planning of training practices that will raise the awareness among cyclists of their bodies and the appropriate adjustments of the bicycle components.
Introduction: Accelerometers are used to quantify energy expenditure in field research. The ActiGraph™ GT1M (ActiGraph™) is a commonly used accelerometer for research. The FitBit ® Ultra (FitBit ® ) is a low-cost alternative to the ActiGraph™; however, there is limited research on the validity of this device. Purpose: The pilot study compares the FitBit ® against the ActiGraph™ and metabolic cart for measurement of energy expenditure and step counts during treadmill walking. Methods: Thirty-two (25 female) adults, mean age 22±2 years, performed two thirty-minute phases of walking (slow and brisk) on a treadmill while concurrently wearing the FitBit ® and the ActiGraph™. Energy expenditure estimates were compared against energy expenditure measured by a metabolic cart. The Pearson's correlation and t-tests determine the linear association and similarity between the accelerometers. Results: Energy expenditure estimate is moderately correlated between the two accelerometers during slow walking (r=0.584, p=0.011) and strongly correlated during brisk walking (r=0.910, p<0.001). Step count is strongly correlated between the accelerometers during slow (r=0.974, p<0.001) and brisk (r=0.996, p<0.001) walking. The FitBit ® significantly underestimated energy expenditure during brisk walking compared to metabolic cart data. There is no difference between the slow and brisk phases' step counts using either accelerometer. Conclusion: The results of this pilot study suggest that the FitBit ® and the ActiGraph™ can be used interchangeably to measure steps, but not to measure kilocalories. Furthermore, the FitBit ® underestimates energy expenditure, compared to a metabolic cart, as exercise intensity increases. This limits its ability to accurately measure energy expenditure in active populations.
This study tested whether hypercapnic ventilatory response (HCVR) is affected by experience in apnoea and explored the possible underlying mechanisms of this phenomenon, with reference to maximum breath hold time (BHT). Elite apnoea divers (EBH=11) and novice subjects (NBH=10) performed a HCVR test (BM), which was repeated by the latter group on another day (PRE) after subjects executed five repeated maximum apnoeas. Subsequently, after a two week period of daily apnoea training, NBH subjects repeated HCVR test (POST). Diaphragmatic activity was recorded to determine apnoea easy going phase. Baseline HCVR of EBH was not lower than that of NBH. After execution of five apnoeas, HCVR in EBH decreased (P≤0.05) whereas it was not different among BM, PRE, and POST conditions in the NBH. Higher BHT and easy going phase values ensued from apnoea maneuvers in EBH than in NBH (PRE and POST), and in NBH POST compared to PRE condition (P≤0.05). HCVR was highly correlated (P≤0.05) with the cumulative easy going phase in EBH, PRE condition but nothing-similar observed in NBH, neither in PRE nor in POST conditions. These results indicate that at rest HCVR is not lower in experienced, than novice, skin divers; this response becomes dull after five repeated maximum apnoeas only in EBH. In the NBH group, two weeks of apnoea training are not adequate to affect HCVR despite an increase of BHT. It appears that after a repeated maximum apnoeas maneuver experienced skin divers improve BHT by extending easy going phase whereas NBH by other means.
Background: Rowing movements can be simulated using specialized ergometers; the method can be used both for training and indoor assessment of body movements within controlled conditions.Purpose: To perform a three-dimensional quantitative analysis of body movements during ergometer rowing, and to examine if there is a relationship between anthropometry and rowing kinematics. Study Design: Descriptive Laboratory StudyMethods: Body movements were recorded in 18 high-level oarsmen during ergometer rowing at 28 strokes/min.The three-dimensional movements of 21 body landmarks (left and right ankle, knee, greater trochanter, hip, shoulder, elbow, wrist, tragus; spinous process of C7, T2, T12, L2, L4) were detected by an optoelectronic instrument.Using dedicated software¸ the range of motion of the posterior angles of the cervical, thoracic and lumbar spine segments relative to the horizontal axis; the angles between greater trochanter-knee-ankle and between knee-ankle and the ground; head rotation and tilt; leg and upper limb symmetry, were computed. Results:The head and neck were approximately in line with the horizontal at catch, and extended at finish, with limited horizontal and frontal plane inclinations.Thoracic spine extension during the stroke was on average 68°.Lumbar spine range of motion was on average 59°, and it was smaller in weightier oarsmen.Upper limbs were symmetric, and a complete, symmetric extension of the lower limbs was made.At catch the legs were nearly perpendicular to the ground. Conclusions:The method allowed the measurement of the kinematic characteristics of the body during ergometer rowing.The measurements agreed with conventional technical teaching.Clinical Relevance: Data collected on high-level rowers can provide a set of standard quantitative execution parameters that can be used by coaches as a benchmark for the assessment of technical movements in all rowers.
Objectives: To assess the body composition of recreational cold-water swimmers, to determine if cold-water swimmers have an increased % body fat when compared to average Americans, and to examine the relationships between body composition and total swim distance and time in the water per swim.Methods: Following 3 months of swimming regularly in cold water in the San Francisco Bay (water temperature range: 9.6° C [49.3° F] to 12.6° C [54.7° F]) during the winter months, body mass index (BMI), % body fat (assessed by circumference technique), and surface/volume ratio were measured in 88 subjects (70 men and 18 women).The total cumulative swim distance was recorded by each subject and each subject estimated his or her average time in the water per swim.Results: For all subjects, averages were as follows: total swim distance in 3-month period (miles[km]): 50.3 [81.0] ± 17.6 [28.3] (range 40 [64.4]-154 [247.8]),average estimated time in the water per swim (minutes): 32.5 ± 7.9 (range 17 -60), age (years): 52.3 ± 10.1 (range: 24-76), BMI (kg/ m 2 ): 25.8 ± 3.4 (range:19.0-37.1),% body fat: 22.6 ± 6.7 (range: 6.9-42.4),surface/volume ratio(m 2 /L): .0259± .0023(range: .0200-.0311).Compared to corresponding American 50 th percentile values, the % fat of men was modestly lower (Median of the difference =-1.6%;P=0.007); the % fat of women was modestly higher, but not statistically different (Median of the difference =1.7%; P<0.1).There was a marginal nonlinear correlation between % fat and average estimated time in the water per swim (Coef.=0.007;P=0.048).No body composition variable correlated with total swim distance (P>0.1 for all variables). Conclusion:Our results suggest that recreational cold-water swimmers do not have an increased % body fat when compared to average Americans, and individuals with a wide variety of body types are able to swim recreationally in cold water.The marginal correlation between % fat and average estimated time in the water suggests that leaner swimmers voluntarily limit time in cold water.
Background: Little kinematic or kinetic information is available to understand risks associated with water skier falls.The present study assessed accelerations during low-speed falls and then contrasted these data against information obtained from automotive crash tests to better delineate risk of injury.The goal was to establish baseline impact information for low-speed falls during water skiing.Methods: Twenty-seven experienced skiers were asked to deliberately make replicate forward falls at 20 miles per hour.A three-axis, electronic, waterproof accelerometer monitored either the torso or head during these maneuvers and recorded the magnitude of impacts in multiples of the force of gravity (e.g., 'g's').Both anatomical sites were assessed for each participant.Data were averaged for the replicate runs.Using these averages, grand means were calculated for accelerations encountered along each of the three orthogonal axes measured.As well, 95% confidence intervals of these grand means were calculated.Peak accelerations were identified for each of the three orthogonal axes measured and plotted against time to estimate durations of acceleration events (impulse).Results: Grand means for torso accelerations ranged from 2.7 g's (95% CI: 1.6-3.9) to 3.6 g's (95%CI: 2.5-4.6).Grand means for head accelerations ranged from 2.5g (95%CI: 1.6-3.4) to 2.6g (95%CI: 1.4-3.8).Peak accelerations did not exceed 44 g's for any participant.The average duration of these accelerations was approximately 110 milliseconds. Conclusions:The average magnitude of accelerations during low-speed water skier falls approximates 2-4g's for either the head or torso.Based on a recent report of a 50-g threshold for brain injury, these impacts pose little risk of serious injury.
Introduction: Measuring oxidative stress (OS) and antioxidant reserve (AOR) may be useful in assessing the physical condition of athletes taking part in competitive sports activities. Aim: During the "Giro d'Italia" in May 2011, the redox state of an entire cycle racing team was monitored to determine the risk of cyclists developing "redox inflammation", which might herald the onset of pathological conditions. Materials and Methods: The nine members of the Liquigas cycle racing team were analyzed using a FRAS 4 Evolvo System. OS was determined by measuring plasma hydroperoxides (d-ROMs test) and AOR by measuring water-soluble antioxidants in the plasma (BAP test). The latter was expressed in terms of μEq of Vitamin C. Both measurements were carried out at four different times during the race: baseline, in the morning two days before the start (B); in the morning of the rest day after 9 stages (M1); in the evening after the most stressing mountain stage (MS); in the morning before the start of the last stage (M2). Each cyclist's performance was determined at the end of the race according to an ordinal scale ranging from 1 to 9. Results: The d-ROMs test values (M ± SD) increased over time from 245 ± 17.2 to 322 ± 50.9 CARR. U. (1 CARR.U. corresponds to 0.08 mg/dL of H2O2). The BAP test values dropped from 2574 to 1962 μEq of Vitamin C. Athletic performance was directly correlated with increases in OS (Spearman rs = 0.714 p 0.05). Conclusions: Redox balance assessment is a useful tool to: a) monitor athletic performance and predict the onset of redox inflammatory state (RI), which might be detrimental to the athlete's physical condition; b) propose suitable supplementation with particular foods and dietary supplements.
Purpose: This investigation examined the effects of Acqua Lete® bicarbonate calcic mineral water ingestion on blood lactate, glucose, and serum lactate dehydrogenase. Methods: 88 amateur male athletes underwent two experimental trials with modified Wingate test: the first was carried out without hydration (Test C), the second (Test H) with hydration following this scheme: 44 subjects (Group A) hydrated by a very low mineral content water and 44 subjects (Group B) hydrated by Acqua Lete ® . Measures of body temperature, (La - ), glucose, total LDH and its isoenzyme pattern, were taken before (T0), during (T1-T5), and after exercise (T6-T7). Results: Blood lactate significantly increased after the session of exercises in both groups: after hydration and 30' of resting (T7) Group B returned a level of lactate lower than the Group A (2.2±0.2 vs 2.9±0.3mmol/L; p<0.001). In Test H, LDH activities after exercise did not change but serum LDH5 isoenzyme activity decreased by 0.9% in athletes in Group B compared to Group A (p< 0.05). Conclusions: All the athletes (Group B) hydrated pre-exercise with Acqua Lete® showed a significant decrease in blood lactate levels post-exercise and changes in LDH isoenzymatic pattern compared with athletes hydrated pre-exercise with a low mineral content water.
Sequence variations in genes that code for proteins involved in homeostatic processes within tendons may influence tendon mechanical properties.Since variants of the four genes COL5A1, TNC, MMP3 and GDF5 have been implicated in the aetiopathogenesis of tendinopathies, which is ultimately characterised by abnormal structural and regulatory processes, sequence variations in these four genes may also influence how the tendon functions mechanically, even in the absence of tendinopathy.For example, two reports of association between variation in the COL5A1 gene and measures of flexibility complement reported associations between genotype and incidence of tendinopathy.Non-genetic factors such as age, body mass and physical activity status influence risk of tendon injury and physical performance potential independently from genomics, and also in gene-environment interactions.However, these non-genetic factors are often not considered in genetic association studies, probably due to their retrospective nature.Further research examining COL5A1, TNC, MMP3 and GDF5, as well as other genes that may influence the maintenance of tendon homeostasis such as COL1A1 which regulates the production of collagen type 1, the most abundant structural component of tendon is encouraged.Establishing the genetic basis of tendon properties in asymptomatic populations may advance understanding of some aspects relevant to physical performance and of the aetiology of tendinopathies.To improve understanding, accurate and reproducible assessments of tendon properties are required.However, no valid and reliable assessments of tendon properties, such as those involving in vivo ultrasound imaging techniques, have yet been applied to genetic association studies in humans.
It is not known if manipulating velocity within a prescribed resistance training mode will improve muscle activation.Muscle activations of the Rectus Femoris (RF), Vastus Lateralis (VL), Vastus Medialis (VM) and Bicep Femoris (BF) were examined during a leg extension exercise at 3 different velocities on 15 subjects (10men, 5 female, Age = 21.5 ± 1.8 yrs, Height = 171.2± 12.5 cm, Mass = 75.5 ± 16.3 kg).Trials of 1 set of 10 repetitions at 60% of 1RM, were performed at 15, 30 and 60º/s.Bipolar surface electrodes were placed over the BF, RF, VL, and VM.Micro-switches were utilized to identify the concentric (CON) and eccentric (ECC) phases of the lift.Data were sampled at 1024 Hz, filtered, rectified and the mean, integrated EMG calculated.One 2 x 4 x 3 (action x muscle x velocity) ANOVA with bonferonni adjustment was run and significance was followed by Tukey HSD post hoc analysis.Results indicated significantly greater activation of the VL, RF and VM for ECC extension at 60º/s compared to 15º/s.While 60º/s was also greater than 30º/s for the VL and VM during ECC.While comparing muscle action, CON VL, VM and RF were greater than ECC at 30º/sec, meanwhile VM CON was also greater at 15º/sec.No differences in muscle activation at any velocity or muscle action for BF were identified.We conclude that muscle recruitment while training with a 60% 1RM load is maximized at a velocity of 60º/s during ECC activity and 15 or 30º/sec during CON.
Hypertrophic cardiomyopathy (HCM) is the number one cause of sudden cardiac death in elite athletes.This project used resting 12-lead electrocardiography (ECG) and ballistocardiography (BCG) to assess cardiac cycle timing events as simple screening techniques to rule out cardiac abnormalities for the safety of a group of elite ice hockey players.Clinical cardiac (ECG) and physiological (maximal aerobic power [VO 2 max], anaerobic [Wingate peak power, Watts] and musculoskeletal strength) data is presented here on an elite group of ice hockey players (n=34; age=17-18 yrs) that participated in a professional medical and fitness evaluation.Subsequently one subject was diagnosed with #1 Apical HCM and his cardiac data is compared with the group.The HCM subject performed all fitness testing and was determined to be physically fit (%BF=7.2%;VO 2 max=59.4mL•kg -1 •min -1 ; Wingate peak power output=15.1 Watt•kg -1 ; Heart Rate max=200 beats•min -1 ).However, the ECG showed extreme voltage and deeply inverted T-waves, and the BCG showed abnormal waveform complexes and cardiac timing events in comparison to the group means.Mean BCG systolic timing events for isovolumic contraction time (54.7±7.1 vs 49.5±12.4msec), acceleration time (49.1±1.8 vs 56.3±9.1 msec), diastole (470.8±25.3vs 531.4±166.7 msec), and isovolumic relaxation time (88.5±7.4 vs 100.8± 16 msec) were significantly different (p<0.05).Atrial systole amplitude was statistically higher for this subject (9.2±3.7 vs 5.3±3 mG).Subsequent follow-up assessment showed abnormal echocardiogram (Echo) dimensions (ventricular septum [12mm]; posterior wall [16 mm]), velocities (mitral valve deceleration [233 msec], LV systolic strain [14%]), and volumes (LV stroke volume [38 mL•metre -1 body surface area]), with normal E:A ratio (1.75) and LV ejection fraction (62%).Cardiac magnetic resonance imaging (MRI) showed apical septal wall thickness (24-25 mm) in the HCM player.In conclusion, BCG was able to corroborate a cardiac abnormality that was later confirmed with echocardiography and MRI, suggesting that BCG is a potential technology to detect anomalies that alter cardiac timing and amplitude.
The level of athletic performances is commonly rated with the International Association of Athletics Federations (IAAF) score value.For running events, this scoring system proved to be strongly based on the total power output corresponding to a given performance.The aim of this study was to develop a semi-objective rating system for competitors in 800-1500m races based on the correlation between IAAF scores and anthropometric parameters.The study was carried out in top Ethiopian athletes, with IAAF score ranging 976-1113 for men and 1008-1093 for women.Significant regressions with negative slope were found in both sexes by plotting individual IAAF score vs sum of skinfold (biceps, triceps, subscapular, and suprailiac) as well as vs BMI/sum of skinfold ratio.We also related the increase in heart rate (HR) to the mechanical power output during an exercise test on a variable inclination treadmill through an exponential regression of the type Y=Y0+A*exp(B*X), where Y0 represents the asymptotic value of HR at the highest work load.Significant relationships with negative slope were found by plotting IAAF score vs Y0 in both sexes indicating that a lower cardiac burden at any mechanical load corresponds to a higher athletic fitness.
The relationship between two menstrual cycle phases and cardio respiratory fitness in athletes on oral contraceptives and not on oral contraceptives was assessed in a pilot study. Twelve endurance-trained college cross country runners underwent maximal oxygen consumption treadmill testing, during the late follicular/ovulatory phase and late luteal/premenstrual phase of their menstrual cycle. No significant differences were detected in maximal oxygen consumption between the oral contraceptive group and non-oral contraceptive group or between the two phases. There was a non-significant phase effect in the non-oral contraceptive group with maximal ventilation averaging 90.5±14.6 L/min during the late follicular/ovulatory phase and decreasing to 79.1±9.8 L/min during the late luteal/premenstrual phase (p=0.102). Maximal ventilation was significantly lower by 15.6% between oral contraceptive and non-oral contraceptive users during the late luteal/premenstrual phase (93.7+7.2 L/min vs 79.1+9.8 L/min, p=0.014, respectively). There was no significant phase effect in the oral contraceptive group for maximal ventilation. While oral contraceptive use was associated with an attenuation of the negative effect of the late luteal/premenstrual phase on ventilator performance, there was no effect on maximal oxygen consumption.
Snowboarding Halfpipe (HP) is a winter action sport which has progressed from being a recreational snow activity to a high performance snow sport such as traditional downhill or Nordic skiing. Like figure skating, gymnastics and diving, performance in the snowboard HP is subjectively assessed by a number of judges. The marking criteria focus on jump height (amplitude) and trick difficulty as the primary technical aspects. However, overall style and the appearance of effortless motion are also essential components of a well scored run. While HP performance is very technical in nature, considerable physical capabilities are required in order to maximize jump amplitude and remain injury free. This paper examines the scientific basis of the HP to highlight the role that sports scientists and strength and conditioners can play in this sport. Challenges that these practitioners may experience with these athletes are also discussed. Further research is required to characterize the physical capacities of elite HP snowboarders and how these compare to the stresses that training and competing may place on the human body. Such information may allow strength and conditioning coaches and sports scientists to develop more specific conditioning programs and to have a clearer understanding of the volume, intensity and mode of training athletes require and can tolerate in order to optimize their HP performance.
Purpose: Several studies analyzed muscle activity after pre-fatigue due to co-contraction, but the effects of antagonist contraction on agonist muscle performance are still incompletely known.The purpose is to determine if a previous workout of an antagonist muscle can affect muscular fatigue appearance during the subsequent agonist muscle performance.Methods: Surface EMG was used to estimate biceps brachii muscle fatigue during isometric contraction executed after previous contractions of the antagonist muscle.Eight expert male body-builders performed five series of isometric contractions (30 s) alternatively according to the agonist and antagonist protocols.Results: Within each repetition, for both biceps brachii muscles and experimental protocols, data showed a progressive fatigue, but no continuous quantitative decreasing trend of the median frequency of the spectrum along the five repetitions.Contraction time explained 1-91% (r 2 values) of the reduction of mean activation frequency along the 30 s (agonistic protocol); 0.7-92% for antagonistic protocol.The decrement in median frequency was only partially timerelated.A repeated measures Anova found significant differences between subjects (p<0.0001),protocols (antagonistic greater than agonistic, p=0.03), while between sides (p=0.93) and repetitions (p=0.50), and for all interactions no significant differences were found. Conclusion:The present results did not confirm that the antagonistic pre-fatiguing can delay the fatigue appearance during agonistic performance (isometric tasks).Accordingly, the antagonistic protocol does not seem to be functional in improving the upper arm performance from a fatigue point of view, at least in trained subjects.
Background: The purpose of this study was to evaluate the effects of short term (12 day) Coenzyme Q10 (CoQ10) supplementation on blood oxidative stress biomarkers and physical performance in young swimmers.Methods: Sixteen young swimmers (7 males and 9 females, aged 15.13±0.96years) who were involved in a sport hero project at Chiang Mai province participated as subjects during this 22 day study.Regular training for swimmers was carried out for the first 9 days.Supplementation with 300mg CoQ10 (Soft gel; Swanson Ultra, USA) was then administered daily for 12 days.Blood samples were collected in EDTA-anticoagulant tubes before (days 1 and 9 of the control period) and after the 12 day supplementation period (day 22).Plasma was separated and used for the determination of malondialdehyde (MDA), nitric oxide (NOx), protein hydroperoxide (PrOOH), total antioxidant capacity (TAC), and CoQ10; whereas reduced glutathione (GSH) was measured in erythrocytes.Exhaustive exercise time was evaluated before (days 1 and 9) and after-supplementation (day 22) on a mechanical treadmill using a modified Bruce protocol.Swimming speeds for both 100 and 800 meters were also recorded.Repeated measurement and Bonferroni correction were used for statistical analysis (p = 0.05).Results: Over the course of the 9 day control period before supplementation, all parameters (MDA, NOx, PrOOH, CoQ10, GSH, TAC, treadmill exhaustion time, and swimming time for either 100 or 800 meters) did not differ (p>0.05).After CoQ10 supplementation, the levels of plasma MDA, NOx, and PrOOH were significantly decreased when compared to the pre-supplement period (p<0.05).Moreover, plasma CoQ10 (2.34±0.78μg/ml vs 1.10±0.38μg/ml) and erythrocyte GSH (14.51±1.99vs 8.90±1.84μmol/g Hb) significantly increased (p<0.05).Maximal treadmill time was increased significantly (22.92±4.89mins) when compared to pre-CoQ10 supplementation (p<0.05),whereas, the swimming time improved significantly for 100 meters when compared to pre-supplementation (p<0.05), with no difference in swim time recorded for 800 meters (p>0.05). Conclusion:Twelve days of CoQ10 supplementation reduces oxidative stress, improves running time until exhaustion, as well as short distance swim sprint time, within a sample of young swimmers.
