Trained Amateur Research Articles

Impact of Leg Strength on the Force Produced During a Cross-Punch in Highly Trained Amateur Boxers.

Satkunskiene, D, Bruzas, V, Mantas, M, Snieckus, A, and Kamandulis, S. Impact of leg strength on the force produced during a cross-punch in highly trained amateur boxers leg strength impact on cross-punch force. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to determine the impact of leg strength on force generation during the execution of a cross-punch by highly trained amateur boxers. This study involved 12 male, amateur boxers with a body mass range of 64.5-112.2 kg and a mean of 89.2 ± 17.0 kg. This study used an isokinetic dynamometer to measure the peak torque of the knee extensor and flexor muscles at 60°/s. The force plate was used to collect three-dimensional ground reaction forces (GRF), moments (GRM), and the center of pressure (COP) during a maximal cross-punch. The Kiktest-100 system was used to determine the force of the punch, while the Hykso punch tracker accelerometer measured the maximum fist velocity. This study revealed a positive correlation between knee extensor strength and GRFz, GRFy, and COPy during punch performance. In addition, the GRMz gradient and GRMz impulse during the execution phase have a significant positive effect on cross-punch force. In conclusion, the force of a straight punch in highly trained, amateur boxers is related to a greater angular velocity about the vertical axis during body rotation.

Data base of Characterization of self-reported sleep quality in male and female trained amateur triathletes: a descriptive study

Sleep quality is a determining factor for the performance and health of athletes in general. The aim of the present study was to characterize the sleep quality in male and female trained amateur triathletes aged 20 to 59 years. A survey was conducted with 151 trained amateur triathletes, 108 male (38.6 ±8.1 years, triathlon training experience 5.8 ±4.3years, training frequency 6.3 ±0.9 days per week) and 43 female (39.3 ±7.6 years, triathlon training experience 4.8 ±3.3years, training frequency 6.5 ±0.6 days per week). The sleep quality was measured using the Pittsburgh Sleep Quality Index-Br (PSQI-Br), total values below 05 points indicate good sleepers, and values equal to or greater than 05 points indicate poor sleepers. Data from the subscales were analyzed using absolute and relative frequency. The other data in order to characterize sleep quality were analyzed with median, mean, standard deviation, standard error, and 95% Confidence Interval of mean. Male and female triathletes have poor sleep quality (values equal or greater than 05 points), that can have negative effects on health and performance. In conclusion, all triathletes regardless of gender and age group have poor sleep quality.

Characterization of self-reported sleep quality in male and female trained amateur triathletes: a descriptive study

Sleep quality is a determining factor for the performance and health of athletes in general. The aim of the present study was to characterize the sleep quality in male and female trained amateur triathletes aged 20 to 59 years. A survey was conducted with 151 trained amateur triathletes, 108 male (38.6 ±8.1 years, triathlon training experience 5.8 ±4.3years, training frequency 6.3 ±0.9 days per week) and 43 female (39.3 ±7.6 years, triathlon training experience 4.8 ±3.3years, training frequency 6.5 ±0.6 days per week). The sleep quality was measured using the Pittsburgh Sleep Quality Index-Br (PSQI-Br), total values below 05 points indicate good sleepers, and values equal to or greater than 05 points indicate poor sleepers. Data from the subscales were analyzed using absolute and relative frequency. The other data in order to characterize sleep quality were analyzed with median, mean, standard deviation, standard error, and 95% Confidence Interval of mean. Male and female triathletes have poor sleep quality (values equal or greater than 05 points), that can have negative effects on health and performance. In conclusion, all triathletes regardless of gender and age group have poor sleep quality.

Training program in the lowlands for amateur mountaineers for climbing to the peaks

Purpose: We develop and experimentally substantiate the use of a method of training amateur mountaineers in conditions of flat terrain to high altitude and ascent to the top.
 Material and methods: The study involved 12 men (age 20-25 years old) who have 1 year experience in mountaineering. The participants were divided into two groups, control and experimental, 6 people each. The study was conducted from March to August 2021. The intervention program lasted 9 weeks. All participants gave their consent to participate in the experiment.
 Methods: Physical fitness was measured by the 20 squat test. The resting heart rate was measured while standing. Psychophysiological condition was determined with the "International Reaction Test", the test shows the reaction time to a stimulus. Altitude was chosen as an influence factor on reaction time and HR in different test modes: initial testing (plain), testing at an altitude of 1900 m and at an altitude of 3200 m.
 Results: The altitude factor had no significant effect on preload reaction time in both control and experimental groups (p>0.05). However, a significant influence of altitude on post-load reaction time was found in both control and experimental groups (p<0,05). HR was significantly influenced by altitude in both control and experimental groups. However, the effect is stronger in the control group than in the experimental group.
 Conclusions. The method increasing tolerance in hypoxia has a positive effect on the organism recovery after the stress in conditions of natural hypoxia, observed during climbing in the mountains.

Assessment of the knowledge of people training amateur strength sports about the squat and its variations and the benefits from this fact

EntryThe squat pattern is present in the life of every human being from his earliest years. In sports, the squat is one of the most popular exercises, used in almost every discipline in countless variations by both professionals and amateurs. Due to its biomechanics and the degree of involvement of the nervous system and the musculoskeletal system, its use is an essential training link in any plan aimed at developing muscle mass, strength and endurance. The squat pattern is also used in medicine, rehabilitation and improving people suffering from all kinds of injuries and dysfunctions of the locomotor system. Material and methodsThe study used the diagnostic survey method, with the use of a proprietary questionnaire consisting of 37 questions. The study was conducted among a group of 250 men aged 20-50 practicing amateur strength sports. ConclusionsThe current state of knowledge about the squat technique (high bar, low bar, front squat) among men practicing strength sports as amateurs is at an insufficient level. Respondents did not show sufficient knowledge about the impact of squats on the human body.

Enduring stress: A quantitative analysis on coping profiles and sport well-being in amateur endurance athletes

Endurance athletes experience physical and psychological stress during training and competition that can inhibit performance and promote negative health implications (i.e., lower well-being) without proper coping mechanisms (McCormick et al., 2018; Sakar & Fletcher, 2014). Additionally, these athletes that train at an amateur level have received limited attention regarding coping with stress and how it impacts well-being (McCormick et al., 2018). The purpose of this study was threefold: to (a) determine common coping profiles of trained amateur endurance athletes, (b) explore the relationship between sport well-being and these coping profiles, and (c) examine the potential roles that appraisals might play in the coping-well-being relationship. The results yielded five distinct coping profiles: Mixed Adaptive Copers (MAC), Mixed Maladaptive Copers (MMC), Engaged Copers (EC), Avoidant Copers (AC), and Social Copers (SC). Coping profiles differed across various variables including sport well-being, appraisals, and demographic factors. Overall, MAC and EC had higher levels of sport well-being. MAC viewed stressors as a challenge (i.e., opportunity) compared to EC and AC. These findings suggest the complex nature of coping in sport and that athletes should develop an assortment of coping strategies that provide different strategies for various stressful situations.

First-person video recordings with eye tracking glasses and cognitive task analysis as a framework for referee decision training

ABSTRACT Rationale In comparison to players little is known about how sports officials integrate perception and cognition to manage in-game decisions. Design Using a naturalistic approach this paper uses first-person eye-tracked video footage to document the attentional demands and situation awareness (SA) of expert touch (rugby/football) referees in their real-world environment to inform decision training for amateur officials. Drawing directly from match performances, an applied cognitive task analysis (ACTA) technique investigated how three international referees manage complex attentional demands, to see what lessons could be learned for less-experienced referees. Findings Referees emphasised the importance of role clarity and game understanding as the foundation for effective match officiating. They used advanced cues such as player body language and movement patterns (SA1) to interpret game status (SA2) and predict likely actions and movement patterns (SA3). Ordering abstraction, preventive communication and early positioning were used to lessen cognitive load and encourage game flow. Practical Implications The merits of using first-person, eye-tracked, audio-visual footage with ACTA for training less experienced sports officials through expert verbal elicitation or self-reflection are discussed. Research Contribution The paper proposes a decision tree for touch refereeing which emphasises a hierarchical ordering of cognitive decision points that provides the basis for training amateur referees.

Metabolic and physiological demands of 3×3-min-round boxing fights in highly trained amateur boxers.

The aim of this study was to evaluate the energy requirements of the aerobic oxidative, anaerobic lactic (glycolytic), or anaerobic alactic systems in highly trained amateur boxers during a 3×3-min-round boxing fight. On three separate occasions, 10 highly trained male amateur boxers undertook a progressive treadmill run, a progressive bag-punching exercise, and a full-contact competitive boxing fight of the 3×3-min format. Expired gas and heart rate (HR) were recorded throughout all exercise tasks, with the exception of a gas analysis during the competitive fight. Total energy expenditure and the contribution of the three major energy-supply systems were calculated based on oxygen uptake (V̇O<inf>2</inf>) and HR during exercise, blood lactate accumulation, and excess V̇O<inf>2</inf> during the fast phase of the recovery. The blood lactate concentration was >15 (range: 12-18) mmol·L-1 after the fight. The HR reached >93% of the maximal (HR<inf>max</inf>) in rounds 1 and 2 and >97% in the final round and was strongly correlated with HR<inf>max</inf> (r=0.885). The average calculated O<inf>2</inf> uptake during the boxing fight was 89% of V̇O<inf>2max</inf>, whereas O<inf>2</inf> uptake equivalent calculated from the involvement of all three major energy supply systems was 122% of V̇O<inf>2max</inf>. The calculated energy provision during the fight was 73% aerobic, 19% anaerobic alactic and 8% anaerobic glycolytic. In highly trained male amateur boxers, 3×3-min boxing match elicits very high HR and blood lactate levels with predominant involvement of aerobic and substantial contribution of anaerobic alactic energy systems.

Sports injuries in indoor volleyball in people who play professionally and as a hobby

Introduction: Volleyball is a sport that causes injuries very often. They often result from the lack of an appropriate warm-up, the intensity of exercises that do not match the body's capabilities, or the use of inadequate techniques and poorly selected sports equipment. The aim of the study was to compare the injuries of people who play volleyball professionally with people who play volleyball.Material and methods: The research was conducted among 144 volleyball players - 75 women (52.08%) and 69 men (47.92%). They were in three age groups: 18-20, 21-25 and over 25 years of age. The group was divided according to the type of game, i.e. whether it is a professional (49.31%) or a hobbyist (50.69%). Each of the volleyball players completed the questionnaire.Results: The group playing volleyball professionally comprised 71 people (49.31%), while the amateur group comprised 73 people (50.69%). Among people professionally training volleyball, injuries were observed in 64 (90.14%) people, while among people training amateur volleyball, injuries occurred more often in as many as 70 (95.89%) people. The most common trauma in the first and second groups was sprain, which occurred in the first group in 27 (38.03%) people, and in the second group - 26 (35.62%).Conclusions: Sprains are the most common injuries among people who play volleyball professionally and as a hobby. Most people who play volleyball professionally after an injury benefited from rehabilitation.

Relationships Between Punch Impact Force and Upper- and Lower-Body Muscular Strength and Power in Highly Trained Amateur Boxers.

Dunn, EC, Humberstone, CE, Franchini, E, Iredale, KF, and Blazevich, AJ. Relationships between punch impact force and upper- and lower-body muscular strength and power in highly trained amateur boxers. J Strength Cond Res 36(4): 1019-1025, 2022-This study examined the relationship between upper- and lower-body strength and power characteristics and punch performance in 28 highly trained male amateur boxers. Punch performance was assessed with a custom-built punch integrator using a 3-minute maximal effort punch test that contained straight- and bent-arm punches from the lead and rear hands. Peak punch force and force-time variables including impulse and rate of force development (RFD; calculated to various points) were assessed. Force, power, and RFD of the upper and lower body were assessed with countermovement bench throw, isometric bench push, countermovement jump (CMJ), and isometric midthigh pull (IMTP) tests. Correlation and regression analyses revealed significant (p < 0.05) relationships between peak punch force and forces measured in CMJ and IMTP tests. In addition, peak punch force was moderately and significantly correlated to body mass, but RFD in the lower body was not. Moreover, no meaningful relationships between punch performance characteristics and any upper-body strength or power parameter were identified. The results of this study show that lower-body strength but not RFD had a moderate to strong positive and significant correlation to peak punch force production. Although upper-body strength and power are expected to be important in boxing, they did not discriminate between boxers who punched with higher or lower peak force nor were they correlated to peak punch force. Training that improves lower-body strength without increasing total body mass (to maintain weight category) may positively influence punch capacity in highly trained amateur boxers.

Menstrual disorders in amateur dancers

BackgroundRigorous exercise undertaken by young girls, combined with a negative energetic balance, is related to substantial physiological changes in a competitor’s body, often leading to hormonal imbalance manifested by: delayed puberty, delayed menstruation, menstrual disorders, and even long-term secondary amenorrhoea. Very lean competitors, with insufficient body fat content, are not capable of maintaining oestrogen production at an optimal level, which results in hypothalamic-pituitary-gonadal axis abnormalities and menstrual disorders. Studies involving research on menstrual disorders in amateur dancers are scarce. Therefore, the aim of the study was to investigate whether menstrual disorders are present among young amateur dancers.MethodsThe study involved 233 females of a mean age of 22.1 years (SD ± 4.9), training amateur ballroom dancing. The questionnaire included questions regarding the regularity of the menstrual cycle, including the absence of a menstrual period, causes of menstrual disorders and breakthrough bleeding.ResultsMenstrual disorders following a period of regular menstruation were reported by 132 (56.7%) of ballroom dancers. In 105 (79.5%), the absence of a menstrual period lasted for less than 3 months, in 18 (13.6%) it persisted for 3 up to 6 months, while in 9 (6.8%) it lasted for over 6 months.ConclusionsThe research conducted concluded that with an increased number of hours spent in training by amateur dancers, there was a statistically significant increase in the chance for menstrual disorders; the more training sessions per week there were, the longer the breaks in menstruation were noted.

Fibre-type-specific and Mitochondrial Biomarkers of Muscle Damage after Mountain Races.

Consequences of running mountain races on muscle damage were investigated by analysing serum muscle enzymes and fibre-type-specific sarcomere proteins. We studied 10 trained amateur and 6 highly trained runners who ran a 35 km and 55 km mountain trail race (MTR), respectively. Levels of creatine kinase (CK), CK-MB isoform (CK-MB), sarcomeric mitochondrial CK (sMtCK), transaminases (AST and ALT), cardiac troponin I (cTnI) and fast (FM) and slow myosin (SM) isoforms, were assessed before, 1 h, 24 h and 48 h after the beginning of MTR. Significant SM increases were found at 24 h in the 55 km group. Levels of CK, CK-MB, AST and cTnI were significantly elevated in both groups following MTR, but in the 55 km group they tended to stabilize in at 48 h. Using pooled data, time-independent serum peaks of SM and CK-MB were significantly correlated. Moreover, concentration of sMtCK was significantly elevated at 1 and 24 h after the race in the 35 km group. Although training volume could confer protection on the mitochondria, the increase in serum CK-MB and SM in the 55 km group might be related to damage to the contractile apparatus type I fibres. Competing in long-distance MTRs might be related to deeper type I muscle fibre damage, even in highly trained individuals.

Green Tea Extract Preserves Neuromuscular Activation and Muscle Damage Markers in Athletes Under Cumulative Fatigue.

A main implication of cumulative fatigue is the muscle damage that impairs neuromuscular function and training adaptations. These negative effects may limit performance when athletes exercise in consecutive days. In this regard, antioxidant supplementation has gain popularity among athletes. Green tea supplementation has been advocated as a strategy to improve exercise recovery due to the activity of its catechins with high antioxidant and anti-inflammatory potential. Here we performed a triple blinded placebo control experiment to determine the effect of green tea extract (GTE) from Camellia sinensis on muscle damage, oxidative stress, and neuromuscular activity in athletes submitted to consecutive sessions of exercise and fatigue. Sixteen trained amateur male athletes were randomly assigned to a GTE supplemented (500 mg/day) or placebo group during 15 days. Effects of supplementation were tested during repeated trials of submaximal cycling at 60% of peak power output performed after a protocol for cumulative fatigue of knee extensors. Muscle damage and oxidative stress showed lower magnitudes in response to fatigue after GTE supplementation. Placebo group showed impaired neuromuscular activity and higher muscle damage and oxidative stress compared to the GTE group during the cycling trials under fatigue. In summary, GTE supplementation showed positive effects on neuromuscular function in response to a condition of cumulative fatigue. It suggests GTE supplementation may have potential to serve as a strategy to improve performance and recovery in conditions of cumulative exercise.

Training Amateur Bandsmen to Perform at Functions: COLTEK Band in Perspective

Training Amateur Bandsmen to Perform at Functions: COLTEK Band in Perspective

Frequency of Electrocardiographic Changes in Trained Athletes in the Republic of Macedonia

BACKGROUND:The use of a 12-lead electrocardiogram (ECG) in the screening of young athletes still has some controversies regarding the cost-benefit of the procedure.AIM:We wanted to identify types and frequency of ECG changes in athletes in the Republic of Macedonia as well as its relation to age, gender, duration, frequency and type of sports.METHODS:The study population included 256 trained amateur athletes who were prospectively examined.RESULTS:The 12-lead ECG patterns were considered normal in 19.9% of athletes, with common training-related changes found in 48.8%, while abnormal and borderline ECG changes were present in 6.6% and 24.6% of athletes respectively. ECG changes were more frequent in males than in females without significant difference regarding the age of athletes. There was a significant correlation between more pronounced ECG changes and longer duration of sports engagement, higher duration of sports activity and type of sport practised.CONCLUSION:The prevalence of abnormal ECG patterns in athletes in RM which could indicate structural cardiac disease and greater risk of sudden cardiac death exist in a proportion that should implicate mandatory 12-lead ECG in the pre-participation screening program and further on the regular annual basis.

Rating consumption of confectionery products by persons training amateur

Human health is not defined by the absence of diseases but as a general welfare of a person that allows life full of vigour, enthusiastic performance of daily duties, fulfilling dreams and coping with different environmental conditions. Proper lifestyle should be determined by application of the principles of proper nutrition combined with regular physical activity. The human body works better when it is subjected to daily physical activity and a proper diet. Our social norms, i.e. majority of people lead sedentary lifestyle, lead to improper expression of our genes that results in the development of chronic diseases, referred to as diseases of civilization. The aim of the study was to evaluate the consumption of confectionery by people exercising in the Fit-Max fitness centre in Bydgoszcz as well as respondents’ motivation to undertake physical activity. The study showed that those exercising in Fit-Max were characterized by high physical activity:they attend classes seven days a week on average and devote from 1 to 3 hours per day for a training session selecting different forms of activity. Their main objective is weight loss, improved muscle strength, fitness and better well-being. Respondents have a wide knowledge of the principles of nutrition; however, they do not follow them in everyday life. Only a small number of respondents use restrictive diets. Although BMI of some of the surveyed indicates overweight and obesity according to the subjective assessment, there are respondents who claim that their body build is within the norm. The respondents admit to regular and frequent consumption of confectionery products due to a number of various reasons, despite the performance of physical activity. Although most respondents did not feel remorse after consumption of sweets, they have reduced the amount of food assortment in favour of increased physical activity due to the increase in body weight.

PS 05-56 CENTRAL BLOOD PRESSURE AND WAVE REFLECTIONS AFTER FULL COURSE MARATHON RACE

Objective: Marathon running is aerobic and extremely vigorous exercise. Central blood pressure and wave reflections are independent predictors of cardiovascular risk. We investigated the acute effect of marathon race on central blood pressure and wave reflections. Design and Method: We studied 30 trained amateur marathoners (male n = 28, mean age = 51.6 ± 8.3 years). We measured central blood pressure and augmentation index before and immediate after the Seoul international marathon (18th March 2012). Central blood pressure and AIx (augmentation index) were measured using HEM-9000AI (Omron Healthcare Co., Ltd., Kyoto, Japan). Wilcoxon signed rank test was used to determine the difference between before and after race for blood pressure and AIx. Results: There is no significant change of brachial systolic and diastolic blood pressure before and after marathon. (p = 0.259, 0.494, respectively) However, there is a significant reduction of central systolic blood pressure after race (128.5 ± 16.8 to 115.5 ± 14.5 mmHg; p < 0.001). Marathon race caused a significant fall in both AIx (77.3 ± 11.3 to 57.4 ± 13.4 %; p < 0.001) and [email protected] (72.0 ± 9.3 to 58.1 ± 12.2 %; p < 0.001). Conclusions: The present study found a reduction in central systolic blood pressure without changes of brachial blood pressure. A significant fall in wave reflections was observed after marathon race. There were more or less acute beneficial effects of marathon on cardiovascular system contrary to our concern.

The Effect Of Exercise Cessation In Well Trained Athletes On Non Articular Tenderness Masseurs.

The effect of exercise cessation in well trained athletes on non articular tenderness masseurs and quality of life. The term chronic multisymptom illness (CMI) includes fibromyalgia (FM), chronic fatigue syndrome (CFS), and a wide spectrum of pain disorders. It is characterized by unexplained chronic pain, fatigue, and cognitive and mood complaints. PURPOSE: The goal of the study was to examine the hypothesis that exercise cessation will be associated with symptoms similar to CMI in a well trained amateur athletes. METHODS: The study population comprised of 26 asymptomatic healthy athletes who regularly exercise 6.75 ± 3.65 hrs per week. All athletes were instructed to refrain from physical activity for 7 days. All participants underwent a complete physical exam, rheumatologic assessment including non articular tenderness threshold (using dolorimeter) and tender points. In addition they completed the SF-36 quality of life questionnaire. Assessments were conducted before exercise cessation and after 7 days. RESULTS: Seven days after sports deprivation all subjects were significantly tender by all tender measures (p<0.001) (dolorimeter thresholds and tender point count). As well, there was a significant reduction in the scores for physical role function (p<0.001), emotional role function (p<0.001) and summary sub-scales of the SF-36 questionnaire after exercise cassation. CONCLUSION: Exercise deprivation is associated with change in non articular tenderness threshold and reduction in quality of life scores. This may be associated with the development CMI.

Differential response of plasma and immune cell's vitamin E levels to physical activity and antioxidant vitamin supplementation

To assess the differential response of plasma, lymphocyte and neutrophil vitamin E levels to high-intensity physical activity and to vitamin C and E supplementation. In all, 14 male trained amateur runners (32-36 y old) were randomly divided in two groups (supplemented and placebo), and participated in a half marathon race. The subjects did not take any other supplements than the ones provided for this study. Vitamin C (152 mg/day) and E (50 mg/day) supplementation was administrated to athletes for a month, using a new almond-based isotonic and energetic beverage (supplemented group). The usual dietary habits of participants were assessed using a self-reported 7-day 24-h recall before the day of the study. To avoid the beverage influence, nonenriched vitamin C and E almond-based isotonic and energetic beverage was given to the placebo group. After 1 month, subjects participated in a half marathon race (21 km run). Vitamin E concentration was determined in plasma, neutrophils and lymphocytes before and immediately after the race, and 3 h after finishing the race. Daily energy intake and caloric profile of supplemented and placebo group were not different except for vitamin C and E supplementation. Vitamin supplementation and exercise had no effect on vitamins E levels in plasma. The exercise significantly (P<0.05) increased the lymphocyte vitamin E concentration both in the placebo (+119%) and supplemented groups (+128%), and neutrophil vitamin E content in the supplemented group (+88%). These levels remained significantly (P<0.05) high after the short recovery. After exercise, vitamin E levels in lymphocytes and neutrophils of supplemented subjects were practically twice the levels before exercise, whereas neutrophil vitamin E content of the placebo group was close to those in plasma. After endurance exercise, lymphocytes increased their vitamin E content in the supplemented and placebo subjects whereas this trend in neutrophils was just observed in the supplemented group. The determination of vitamin E content in lymphocytes and neutrophils after exercise is a useful tool to assess the functional status of vitamin E.

Modulation of fundamental frequency by laryngeal muscles during vibrato

The variations in voice fundamental frequency (F0) that occur during vibrato production may be produced, at least in part, by modulation of laryngeal muscle activity. We have quantified this relation by using a cross-correlation analysis of the changes in F0 during vibrato and the changes either in motor unit firing rate or in gross electromyographic activity from the cricothyroid (CT) and the thyroarytenoid (TA) muscles. Two trained amateur tenors provided the data. Correlations were generally quite strong (mean r for the CT was 0.72 for singer 1 and 0.50 for singer 2; mean r for the TA was 0.31 for singer 2), thus providing support for previous evidence that fundamental frequency modulation in vibrato involves active modulation of the laryngeal motoneuron pool, especially by the CT muscle. In addition, phase delays between muscle modulation and changes in fundamental frequency were substantial (averaging approximately 130 degrees for the CT and 140 degrees for the TA). This finding may help provide insight regarding the mechanisms responsible for the production of vibrato.