Sports Training - Wingate and RSA Tests - Essay Example

Swarnambika S Academia Research Sport Training August 28, 2007 Sport Training Wingate and RSA tests Anaerobic power or capa is an expression used for the maximal exercise up to a maximum of two minutes and the energy used during the workload is provided in large measure without necessitating oxygen, since the stored phosphagenes and glycogen in the muscles would be enough up to two minutes. At the onset of the exercise, since ready energy materials are used, lactate is not formed. Later, lactate is formed, since the energy is obtained by breaking down the glycogen without oxygen. Lactate thus formed, is eliminated by the buffer systems of the organism. However, when lactate production is excessive, it accumulates in the muscles and the blood. Meanwhile, if the glycogen stores of the muscles and blood decrease, the exercises slow down and when the aerobic procedures undertaken are not sufficient, the exercise can not be maintained (Astrand & Rodahl, 1987; Fox, Bowers, & Fos, 1988; Weineck, 1986). Lactat is accumulated in the organism after all kinds of muscle exercise having maximal and supramaximal workload. It can even be observed within ten minutes workload (Jacops et al, 1983). The measurements of lactate in the muscle and blood are being done to determine these processes. Lactate measurements during exercise yield information on the intensity of the workload and on its duration. The measurements carried out after the exercise yield information on the frequency of workload and on its scope, that is, on resting-recovery process (Bueno, 1990). Babij found that, after an exercise of 10 minutes where maximal oxygen consumption rate was 50%, there was no accumulation of venous blood, and that, after the same exercise where oxygen consumption rate was 76%, lactate of the venous blood increased up to 5 minutes and then started to decline (Babij et al, 1983). The number of infantile and juvenile competitions has significantly increased over the past two decades (Bar-Or O. 1996; Colantonio et al, 1997; Kemper, 1995; Matveev, 1996), which has favored world records to be broken by 14-year old athletes. One knows well metabolic and functional responses to exercises in adults, whether normal or with impairments (Del et al, 1985; Negrao et al, 1998) but there are many issues that are yet to be solved regarding physical training of children and adolescents (Bar-Or O, 1996). Aerobic fitness is instrumental for children and adolescents, not only for healthfulness8, but also for the practice of a number of sports (McArdle et al, 1996). Human capability of performing mid and long-duration exercises chiefly depends on aerobic metabolism. Thus, one of the main indices used to assess this condition is the maximum oxygen uptake (VO2max), known as aerobic power (Denadai BS, 1995; Kiss MAPDM, 2000). According to literature, in maximum exertion tests, swimmers (S) and water polo players (WP) typically present VO2max values close to 69.012 and 55.513 (ml.kg-1.min-1), respectively. In judo practitioners, it has been observed, from four consecutive Wingate test bouts for upper limbs that oxygen uptake (VO2) in the first bout was lower than that in the second, but there were no differences from the later in the third and fourth bouts, showing a tendency to stabilization. For swimming and water polo, when comparing two consecutive Wingate test bouts for upper (ARMS) and lower limbs (LEGS), and specific tests at the pool, there was good correlation only for ARMS (r = 0.85, p < 0.05) at the second bout, in S (Colantonio et al, 2001). In spite of evidences about mean VO2max values at exercises in which aerobic metabolism prevail, it is interesting to observe its behavior in exercises in which anaerobic metabolism prevail. VO2max may be defined as the highest oxygen (O2) uptake accomplished by an individual breathing air at sea level (Astrand PO, 1952). This variable is one of the main items examined in endurance studies, in spite of the use of the expression oxygen peak uptake (VO2peak) to describe O2 uptake values from any maximum exertion test, with no plateau level between two adjacent loads. More recently, a conceptual difference between energetic system power and capability has been used. Aerobic power (VO2max) is, thus, defined as the maximum amount of ATP produced per unit of time by the aerobic system (Astrand, 1952). Therefore, VO2max equals to the maximum O2 amount a stimulated body may draw from the air, transport to tissues through the cardiovascular system, and use on a cellular level at the unit of time. For many years, VO2max has been used as a parameter to predict performance by many investigators, when assessing athletes performing sub maximal exertion, based on the hypothesis of a strong relationship with maximum endurance performance. In literature we find a number of studies associating athletes of endurance sports, in particular, to high VO2max values. Some reference values may be found in specific literature, such as athletic march = 73.2; mild distance runners = 73.3; marathon = 72.0; road cycling = 78.812, mild distance runners = 75.5 (Billat, 1995); elite rowers = 61.4, cross-country skiers = 85.0 ml.kg-1.min-1 for males. It is also common to find swimmers with high VO2max, such as 69.0 on a treadmill and 55.0 to 75.0 in swimming flume; 68, 6 when comparing swimmers and runners on a treadmill; 50-70 for males and 40-60 ml. kg-1.min-1 for females between 15 and 25 years of age (Wilmore & Costill, 1994). However, for swimming, about 80% of all competitions are of 200 m or less, i.e., with less than two minutes duration. Therefore, training at maximum speed is necessary for adjustments to occur for utilization of anaerobic energy. As in swimming contests anaerobic metabolism prevails, it is fascinating to think why swimmers present such high VO2max values when compared to athletes who practice other, chiefly aerobic sports Few studies have investigated swimmers or water polo players using anaerobic lab and/or field tests, in order to observe their metabolic and functional responses under these conditions, particularly with athletes still under development (Konstantaki, Trowbridge & Swaine, 1998). High-intensity sprints of short duration, interspersed with short recoveries, are common during most team sports (Karu, 2000). Therefore, the ability to recover and to reproduce a high power output in subsequent sprints is an important fitness requirement of team-sport athletes and has been termed repeated-sprint ability (RSA). However, little is known about what limits RSA and how best to improve RSA. The aim of this study was to analyze recent research that have developed methods to improve RSA. While the recovery of 30-s sprint performance has been correlated with PCr resynthesis 3, we have not found the same relationship with the recovery of 4-s sprint performance (r = 0.24). If PCr resynthesis is important for RSA, it is important to know how to improve PCr resynthesis. A cross-sectional research suggested that an elevated aerobic fitness was associated with faster PCr resynthesis. However, a 20% increase in aerobic fitness with training was not accompanied by an increase in PCr resynthesis rate. A decrease in muscle pH (pH) may also be an important limiting factor to the performance of repeated-sprint exercise. The extent of the decrease in pH during muscular activity is dependent upon both the production of hydrogen ions (H+) and on muscle buffer capacity (m). It appears that high-intensity training is required to increase m. However, our research suggests that training too intensely could actually decrease m. While further research is required, it appears that the optimal intensity to improve m is approximately 100% VO2max. Furthermore, despite similar changes in aerobic fitness, training also increases m greater than changes in RSA. Isokinetic Strength Testing Sports personnel are required to perform physically demanding tasks in both training and combat environments. Task requirements often exceed the capabilities of Sports personnel, with serious implications for personal safety and well-being. The mismatch between players and the requirements of their tasks is often manifested as an increase in the incidence of injury. Injury is often ignored as an important factor in success. Isokinetic strength assessments have been shown to have a number of applications in medical, occupational and sports-conditioning settings. An isokinetic contraction is the muscular contraction that accompanies constant velocity limb movements about joint or joints (Baltzopoulos and Brodie, 1989). Isokinetic assessments include the measurement of torque, work and power through a range of motion of a given limb. A number of isokinetic devices are commercially available, including the Cybex, Kin-com, Biodex and Merac systems (Abernethy et al., 1995). Isokinetic testing devices have gained increasing acceptance both as modalities for clinical strength assessment and as means of rehabilitation (Perrin, 1993; Frisiello et al., 1994). A central consideration in the utility of isokinetic data relates to the use of peak torque (Nm) or total work (J) as the indicator of efficient performance. Charteris (1999) states that peak torque usually represents performance at some (usually unspecified) point in the range of motion. Like Perrin (1993) he argues that higher peak torques is not a guarantee of greater total work outputs. He regards "summated torques" or the area under the torque curve as being the superior measure of full-range tension development and therefore work capacity. Hamstring injuries usually occur when a player over strides when running at full speed (Orchard, 2003). Bending over to pick up a ball when running at pace is a particular risk. During these types of movement, the hamstring muscles are relatively more stretched than during a stride of normal length at maximum speed, although they do not reach maximum muscle length. It is not known whether the actual muscle injury in sprinting occurs during the late swing phase (when muscle length and stretch is greatest) or early stance phase (where stress due to ground reaction forces is greatest). The most established risk factors for hamstring strain are age and injury history and regrettably these are not reversible. Another likely risk factor is low strength (usually measured by hamstring to quadriceps [H:Q] ratio of less than 0.60) (Burkett, 1970). Only one study has suggested that hamstring strains can actually be prevented by reversing strength deficits (Heiser et al, 1984). The most important variant of hamstring injury to exclude on the initial examination is a ruptured hamstring origin tendon. These injuries will almost always cause the player to immediately cease running and present with severe hamstring weakness, proximal tenderness, swelling and often bruising. If such an injury is suspected, ultrasound or magnetic resonance imaging (MRI) is indicated as surgical repair of a proximal tendon rupture is required to return to full activity. In the rugby codes, return to play is also dependant on player position. Forwards can often carry hamstring injuries without missing any matches, whereas the prognosis for outside backs is similar to AFL and soccer players, where most players will usually miss at least 2-3 weeks of playing. Return to jogging and non-weight bearing exercise can be accelerated after a hamstring strain, as these activities are very unlikely to stress the hamstring muscle group. Return to full speed running and full training should only occur when normal strength (>90% of the unaffected side) and range of motion have returned (Heiser et al, 1984). Performance at training should dictate whether a player returns for matches. A player is at risk of re-injury for at least 6-8 weeks after return to play, so should only undertake sprinting and other high risk drills with extreme caution in this period. The clinician must convey to the athlete and the coach, that return to play following a muscle strain does not usually coincide with full recovery and healing from the injury. The concept of a player 'carrying' a muscle strain is an accurate expression. In some sports, NSAIDs and cortisone injections are used by some clinicians to promote early return to play after muscle strains (Levine et al, 2000). This use of anti-inflammatory agents is currently a decision based on clinical experience rather than carefully controlled clinical studies. The risk of using anti-inflammatory agents is that healing and scar formation will be delayed, possibly predisposing to recurrence. In some cases, pain from excessive scar formation may delay recovery so there is an argument for use of anti-inflammatory agents if the pain of the injury appears to be out of proportion to the structural lesion (Orchard & Best, 2002). Protocol for Isokinetic Evaluation Postural stability, functional assessment, and isokinetic strength measures were evaluated in 20 subjects (11 men, 9 women) with a history of one surgery for ACL reconstruction (age = 25.8 8.1 years, height = 175.8 8.5 cm, weight = 73.3 14.0 kg) and 20 age- and activity-matched subjects (11 men, 9 women) who served as the control group (age 5 24.5 6 6.9 years, height = 175.8 8.3 cm, weight = 71.4 12.1 kg). Recruited subjects all had ACL reconstruction performed in a similar fashion (arthroscopically assisted central bone-patellar tendon-bone graft). The mean time since surgery was 18 10 months. Activity was matched as closely as possible using sections B and C on the Sports Participation Survey originally described by Seto et al (1988). The study was approved by an institutional review board, and all subjects signed an informed consent form before participating. Isokinetic Evaluation Strength testing was performed for knee flexion and knee extension at 1208 per second and 2408 per second on the Kin Com dynamometer in the seated position. Concentric and eccentric contractions were performed at each velocity. The first extremity and velocity to be tested were counterbalanced to prevent fatigue or learning effects. Subjects were seated on the dynamometer and stabilized with chest and leg hook-and-loop straps according to the manufacturer's guidelines. The axis of rotation of the Kin-Com was adjusted so as to align with the joint margin of the knee. The distal pad of the dynamometer arm was placed just proximal to the malleoli. Before testing, we asked subjects to extend the leg; the weight of the limb was recorded and corrected for gravity using the Kin-Com software package. Before data collection, subjects performed 4 practice repetitions for each velocity setting at 75% of subjective maximal effort. Each concentric contraction was followed by an eccentric contraction for both extension and flexion of the knee joint. After this warm-up phase, a 2-minute rest was given. The evaluation phase consisted of 3 repetitions of maximal concentric and eccentric contractions for extension and flexion of each leg. We informed subjects that they needed ''to push or pull as hard and fast as they can'' against the resistance provided by the dynamometer. Order of testing was counterbalanced to prevent a fatigue or learning effect. A 5-minute rest period was given before the opposite leg was tested. Peak torque values were used as the dependent measure of muscle strength. Statistical Analyses Extremity matching was achieved by matching the injured extremity (right/left) from the ACL-reconstruction (ACLR) subject with the same extremity in the uninjured subject. We used a repeated-measures analysis of variance (ANOVA) with 1 between-subjects factor (group) and 1 within-subjects factor (plane) to determine if differences existed for bilateral postural stability assessed with the BSS. With repeated-measures ANOVA with 1 between-subjects factor (group) and 2 within subjects factors (extremity and plane), we examined differences in single-limb postural stability. A repeated-measure ANOVA with 1 between-subjects factor (group) and 1 within subjects' factor (extremity) was calculated to assess differences in the single-leg hop-for-distance test. We assessed differences between hamstrings and quadriceps knee muscle strength with 2 repeated-measures ANOVAs with 1 between-subjects factor (group) and 3 within-subjects factors (extremity, contraction, and velocity). Tukey Honestly Significant Differences post hoc comparisons were performed for all significant interactions, and all statistical tests were considered significant at the P< .05 level. Results For knee-flexion strength, there were no significant differences between the ACLR (Anterior Cruciate Ligament Reconstructed) and control groups or between extremities. For knee-extension strength, there was a significant interaction for group by extremity (F1, 38 = 9.40, P< .01). Additional significant 2-way interactions were found for extremity by velocity (F1, 38 = 6.03, P < .05) and contraction by velocity (F1, 38 = 103.7, P < .01). Tukey post hoc analysis revealed that ACLR subjects produced significantly greater torque in the uninvolved leg than the involved leg, and the involved limb of the ACLR group produced significantly less torque compared with the matched involved limb of the control subjects (P < .05). Discussion Knee Flexion Exercises that focus on strengthening the hamstring musculature are recommended after ACLR in an attempt to reduce anterior translation forces of the tibia. The lack of a difference in peak torque during knee flexion supports previous findings that after 12 to 14 weeks post-ACLR, knee-flexion strength returns to near-normal levels (Wilk et al, 1992). Our findings are inconsistent with those of Seto et al (1988), who reported that hamstring strength in the reconstructed limb was significantly less than that in the control leg at 120 and 2408 per second for subjects who had an intra-articular ACLR. The reported differences between the Seto et al (1988) study and our investigation may be attributed to the more conservative rehabilitation process that was followed at the time that study was conducted. Knee Extension Aggressive rehabilitation after ACLR commonly employs immediate motion, weight bearing, and exercise to initiate quadriceps contraction (Wilk et al, 1992). However, quadriceps strength is slow to return to normal levels. Our results indicate that ACLR subjects produced significantly more torque with the uninvolved knee than with the reconstructed knee. The strength of the knee extensors for the ACLR subjects may not have returned to pre-injury levels. Similarly, the matched involved knee of the control group produced significantly greater torque than the reconstructed knee of the ACLR subjects. As such, the quadriceps muscle strength of ACLR subjects in our study had not returned to near-normal levels after an average of 18 months after surgical repair. Our findings are consistent with those of Seto et al (1988) and Hoffman et al, (1999) who reported that quadriceps strength in the reconstructed limb was significantly less than that in the control leg for subjects who had an intra-articular ACLR. For comparison, patients in the Seto et al (1988) study underwent an intra-articular or extra-articular ACLR, and patients in the Hoffman et al (1999) study underwent an arthroscopically assisted patellar tendon graft. The differences in strength and function but not in postural stability may be explained by the specificity of the exercise and possible compensation by other lower extremity muscle groups. The ability to perform a single-leg hop depends on the strength of the quadriceps muscle. A decrease in quadriceps strength would result in reduced loading capacity of the knee joint and the inability to absorb and generate force. In addition, the influence of the graft selection cannot be disregarded, as strength deficits of 5% to 34% have been reported after ACLR with the bone-patellar tendon-bone procedure and subsequent rehabilitation. The ability to balance on an unstable platform requires the coordinated activation of the lower leg musculature. While knee extension and the single-leg hop require maximal contraction of the supporting musculature, single-limb and double-limb balance do not. Therefore, the ability to balance on the dynamic platform may not have been a sufficient challenge. The use of different methods to maintain balance has been defined as a strategy. In 1990, Horak et al (1990) described these strategies as ''stereotypical movement patterns in order to achieve or maintain postural stability during anterior/posterior sway with a fixed stance.'' These strategies most often involve using primarily the ankle or the hip for neuromuscular control. 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