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Introduction

    Throughout the history of the sport and physical activity, it has been attempted to improve our physical qualities that enable us to delay fatigue. These adaptations would make it possible for us to maintain a physical activity through time and, in addition, to perform precise and controlled movements. One example is surfboard riding (surfing) a popular sport enjoyed on the beaches of five continents at both the recreational and competitive level. The surfing action is to ride a surfcraft along the unbroken section or wall of a wave, as it inches closer toward the shore. Modern surfing is performed using a foam and fiberglass board with the rider standing erect on his or her feet. Surfing contests are based on elimination heats. The normal contest format consists of 20- to 40 minute heats, in which two, three or four surfers are given scores by a group of judges. The role of judges in a surfing contest is to decide which surfer performs maneuvers closest to the judging criteria in any heat (Mendez-Villanueva and Bishop 2005). Lowdon (1983) has described the surfing process as follows: first of all, the surfboard is paddled out with the surfer in the prone position in order to reach the take-off area, what can last as long as 2-3 minutes. Once there and when a suitable wave approaches, some powerful strokes (about 6 seconds long) are needed to give the board enough speed to be gathered up by the swell. When the wave has been caught, it is necessary to quickly stand up and to perform maneuvers on the wave’s wall until the wave breaks on the beach. At this point, the same process has to be repeated many times (between 4 and 8 times in a competition heat) throughout the surfing session. Therefore, the fatigue effects of arm paddling in postural control should be examined as this is critical for success during surfing once the individual is standing on the surf board.

    Muscle fatigue is a complex phenomenon that has been defined as a reduction in the force-generating capacity regardless of the task performed (Bigland-Ritchie and Woods 1984).

    Excessive workloads can increase physical fatigue, resulting in diminished physical endurance and performance and, ultimately, a reduction in productivity. In addition, a combination of muscular fatigue and general subjective fatigue may also manifest itself by causing temporary interference with the functioning of the central nervous system (CNS) as well as the peripheral nervous system (Gandevia 1998; Lepers et al. 2002). As postural stability is maintained by the CNS as well as the peripheral nervous system, modifications in its performance may diminish one’s ability to sustain balance.

    In recent years, a well publicized area in the literature is the relationship between postural control and fatigue (Caron 2003; Caron 2004; Forestier et al. 2002; Gribble and Hertel 2004; Gribble et al. 2004; Hiemstra et al. 2001; Huston et al. 2005; Robertson et al. 2000; Seliga et al. 1991; Susco et al. 2004; Vuillerme et al. 2001; Vuillerme et al. 2002; Wilkins et al. 2004; Wilkstrom et al. 2004; Yaggie and McGregor 2002). Specifically, postural control can be defined as either static (maintaining equilibrium with minimal movement), semi-dynamic (maintaining equilibrium while the base of support moves), or dynamic (maintaining a stable base of support while completing prescribed movement) (Guskiewicz and Perrin 1996; Olmsted and Hertel 2004). Of the three, static and semi-dynamic have been used the most in past and present studies (Caron 2003; Gribble and Hertel 2004; Seliga et al. 1991; Susco et al. 2004; Wilkins et al. 2004). For example, Gribble and Hertel (2004) looked at the effects of local muscle fatigue on static postural control when measured by a thirty second unilateral stance test, and Camps et al. (2008) looked at the effects of upper body fatigue in static postural control measured by the Romberg test.

    Central or whole-body fatigue, refers to a decrease in the central nervous system output to the muscles (Brooks et al. 1996) and likely has a component that includes factors responsible for the sense of effort in addition to the alterations in motor pathways responsible to maintain equilibrium (McComas 1996). Localized muscle fatigue is induced by a decrease in the metabolic substrates available for muscle contraction, such as adenosine triphosfate, creatine phosphate, and glycogen, as well as an increase in metabolites, including lactic acid, in the muscle, resulting in an inability to maintain a desired muscular force output (Rozzi et al. 2000), this accumulation of metabolites and/or infammatory substances within the muscle during activity to fatigue (i.e. lactic acid or bradykinin), have been shown to elicit increased muscle spindle static and/or dynamic sensitivity via reflex-mediated pathways from chemosensitive group III and IV aferents onto Ɣ-motoneurones (Björklund et al. 2000) what would affect one`s ability to maintain equilibrium due to an incomplete afferent information. An appealing hypothesis can be formulated. It could be that the occurrence of fatigue during upper extremity fatiguing protocol induces a central fatigue, which impacts on postural control.

    Although a good base of knowledge for researchers is the development of an injury model, most athletes do not participate in a static environment. Since most sporting events are dynamic in nature (and so is surfing), they require a unique and complex coordinated effort from various systems of the body to allow the athlete to participate at his/her peak level.

    With this in mind a publication by Gribble et al. (2004) looked at the effects of dynamic postural control and how it responds to a fatigue state. But we did not find any study looking at the effects of upper extremity exercise in dynamic balance. This form of postural control is important in almost any sporting activity whether it be shooting a foul shot in basketball, performing gymnastic exercises, hitting a backhand in tennis or riding a wave in surfboarding where the surfer should maintaining a stable base of support while completing prescribed movement (what fully agree with definition of dynamic postural control). Having proper control of your body allows the individual to concentrate totally on the functional task at hand.

    One test currently in the literature that truly assesses the dynamic balance of healthy individuals is the Star Excursion Balance Test (SEBT) (Earl and Hertel 2001; Gribble 2003; Gribble and Hertel 2003; Kinzey and Armstrong 1998). This test is said to provide a significant challenge to the athlete’s postural control system and shows strong intratester reliability (Earl and Hertel, 2001; Gribble, 2003; Kinzey and Armstrong, 1998).

    One problem with the current research is that it often uses a repeated isokinetic exercise, or an isometric hold to fatigue the muscle or muscle group, these activities are usually not functional or sport related in anyway. Research needs to support a more functional or sport-related fatiguing protocol to observe how rigors of surfboard paddling performed previous riding the wave in surfboarding affects the dynamic postural control system of the body during the wave riding. Therefore in this study we used an activity related test that truly mimics the surfing paddling action before catching the wave.

    Therefore the purpose of this study is to examine how dynamic postural control as measured by the Star Excursion Balance Test, is affected by an activity related fatiguing protocol performed with the upper extremity and simulating the surfboard paddling performed previous catching the wave and how peripheral and central fatigue can affect this postural control.

Material and methods

Subjects

    Forty male sports sciences students (age= 20.6 ± 1.9 years, Height = 175.6 ± 9.7 cm, Mass = 75.5 ± 16.1 kg) were tested twice during 1 session. Any subject who had suffered a musculoskeletal injury to a lower extremity or a head injury in the 6 months before testing was excluded from the study. We screened subjects for any preexisting visual, vestibular, or balance disorders through self-report. Subjects were randomly assigned to one of the two test groups, control or fatigue. All subjects read and signed the informed consent form approved by the institutional review board, which also approved the study procedures.

Procedures

    Each subject performed 6 practice trials in each of the 8 directions for each leg to become familiar with the task, as recommended by Hertel et al. (2000), fatigue and control subjects came in together as a pair.

    We measured leg length of both legs with the subjects lying supine on a plinth using a standard tape measure from the anterior superior ilial spine to the distal end of the medial malleolus at the beginning of the first session. Then both control and fatigue subject performed pretest trial, after that fatigue subject performed the fatiguing protocol as control subject remained seated. Immediately after fatigue subject finished the fatigue protocol, both, control and fatigue subject, performed the posttest trial. Same protocol was repeated on the testing data collection session.

Star excursion balance test

    The SEBT is a functional, unilateral balance test that integrates a single-leg stance with maximum reach of the opposite leg. The reliability of SEBT has previously been established for our specific measurement methods (Hertel et al. 2000). The SEBT was performed with the subject standing in the middle of a grid placed on the floor with 8 lines extending at 45º increments from the center of the grid. The 8 lines on the grid were named in relation to the direction of reach with regard to the stance leg: Anterolateral (AL), Anterior (A), Anteromedial (AM), Medial (M), posteromedial (PM), Posterior (P), Posterolateral (PL), and lateral (L). the grid was constructed in a polyvalent room using a protractor, tape, and tape measure and was enclosed in a 1.83 m x 1.83 m square on the hard rubber floor (Figure 1).

Figure 1. The 8 positions of the Star Excursion Balance test are based on the stance limb

    We provided verbal and visual demonstration of the test to each subject before data collection. We asked the subject to keep their hands on their hips, to keep the heel of the stance leg flush with the testing surface and maintain a single-leg stance on the stance leg while reaching with the opposite, or reach, leg. We asked the subject to reach to the furthest point possible on the line, touching the line as lightly as possible to make certain that steadiness was achieved through adequate neuromuscular control of the stance leg. Test was performed with both leg. The examiner marked the touch point and measured the distance from the center of the grid with a tape measure in centimeters. The subject then returned to the starting stance at the center of the grid maintaining balance. Measurements were taken after each reach. The reach distances were normalized, normalization was performed by dividing each excursion distance by a participant’s leg length, and then by multiplying by 100 (Gribble and Hertel 2003).

    We recorded 3 reaches in each direction separated by 10 seconds of rest. We then calculated the average of these reaches for each of the 8 directions. Reach leg (right, left). Order of reaches performed (clock wise, counter clock wise) and direction of the first reach (A,M,L,P) were counter balanced to control for any order effect. Trials were repeated if the subject touched the line at any point other than the end point with the reach foot while retaining weight bearing on the stance leg, lifted the stance foot from the center grid, lost balance at any point during trial, or did not maintain start and return position for 1 full second. We feel confident that in a recent paper Hertel et al. (2006) demonstrated that 8 directions do not need to be assessed but we did anyway so we could compared our results with previous research in a better way.

Fatigue protocol

    After the familiarization period, all subjects underwent a pretest in which they performed 3 trials with each leg. Subjects in the control group then rested, as long as the duration of the fatigue protocol (15.3 ± 2.2 min), whereas subjects assigned to the fatigue group performed the fatigue protocol, which was immediately followed by posttest. The fatigue protocol was performed lying prone on a table (height 40 cm, wide 30 cm, long 130 cm) and using an arm crank ergometer (Monark 881E, Monark-crecent AB, Varberg, Sweden) (Figure 2).

    The fatigue protocol (Figure 3) mimics the surfing paddling action performed previous catching the wave described before. Starting with 5 minutes of warming up with a continuous intensity of 25 W and 50 rpm, then a 2 minutes of passive recovery took place. The subjects then performed 4 phases, each of one started with a continuous intensity (30 W phase 1, 45 W phase 2, 60 W phase 3, 75 phase 4) in a supporting cadence of 50 rpm (showed in Monark 881E display) during 2 min and 30 s followed by 6 s of maximal power output and 24 s of passive recovery, again to continue with the new intensity. Once come to the intensity of 75 W, maximum power output was realized until the exertion/exhaustion. Before protocol started, during the 24 s recovery period in phase 2, as well as at the exhaustion point, RPE was assessed. It is important to realize that not every subject was able to reach phase 4, but we must be sure every subject quit at his/her point of exertion/exhaustion or reaching RPE levels up to 15 in the 15-point Borg scale (6-20) (Borg 1970) (Figure 3).

RPE

    We used a 15-point Borg scale (6-20) (Borg 1970) to measure ratings of perceived exertion (RPE) in attempt to quantify the amount of exertion displayed by each subject before, midway through, and after the exertion protocol. The 15-point Borg scale has been recommended for applied investigators of perceived exertion and for predictions of exercise intensity during sports (Borg 1982).

Statistical analysis

    Using SPSS software (version 14.0; SPSS inc, Chicago, IL), dependent T test were performed to compare each of the 8 excursions distances of the right and left limbs of subjects. Because no significant differences (P > .05) were identified, data from the right and left limbs trials were averaged. Then we used a two factors ANOVA with Group (control and fatigue) and Time (pre-fatigue, post-fatigue) as the levels. This design tested the main effect of group and pre-posttest, but most interestingly the interaction effect of Group (control and fatigue) x Time (pre-fatigue, post-fatigue). Independent T test were performed to compare RPE values of fatigue and control group at the beginning, mid part and the end of fatiguing protocol. Dependent T test were used to compare pre and post values of 8 reach in both fatigue and control group. We set our alpha level priori at 0.05.

Results

    Our findings did not reveal significant differences (P > 0.05) between each of the 8 excursions distances of the right and left limbs of subjects, therefore data from the right and left limbs trials were averaged.

Table 1. Reach distance of SEBT for 8 directions and total for both control and fatigue group in pretest and posttest

Reach	Control (n=20)		Fatigue (n=20)
Direction	Pretest	Posttest	Pretest	Posttest
Anterior	110.9±15.55	110.9±15.03	115.1±10.48	102.4±4.73*
Anteriomedial	116.7 ± 21.55	116.5 ± 21.41	114.7 ± 16.23	103.4 ± 10.60*
Medial	106.3 ± 27.60	105.1 ± 25.26	103.3 ± 28.19	89.1 ± 23.06*
Posteromedial	114.5 ± 20.79	115.6 ± 18.31	104.1 ± 17.24	96.9 ± 16.48*
Posterior	109.6 ± 19.25	109.1 ± 18.36	101.9 ± 16.04	95.9 ± 13.57*
Posterolateral	108.7 ± 17.60	108.8 ± 17.53	105.2 ± 18.49	95.7 ± 21.71*
Lateral	101.7 ± 29.28	101.7 ± 27.98	108.6 ± 28.03	86.4 ± 17.36*
Anterolateral	116.1 ± 18.12	114.9 ± 14.15	116.7 ± 9.95	103.8 ± 9.50*
Total	110.6 ± 11.50	110.3 ± 10.69	108.7 ± 10.73	96.7 ± 8.35*
Mean ± SD of reach distances in cm for 8 reach distances (Anterior, Anteromedial, Medial, Posteromedial, Posterior, Posterolateral, Lateral and Anterolateral) and total values (mean of 8 values) of Star Excursion Balance Test (SEBT) for both control and fatigue group during pretest and posttest. *Statistically significant (P<0.05) from pretest.

    The two factors ANOVA with Group (control and fatigue) and Time (pre-fatigue, post-fatigue) as the levels showed the main effect of group (P = 0.001) and pre-posttest (P = 0.01) being significant in both cases, but most interestingly the interaction effect of Group (control and fatigue) x Time (pre-fatigue, post-fatigue) (P = 0.013) was statistically significant as well. Mean ± SD of reach distances in cm for 8 reach distances (Anterior, Anteromedial, Medial, Posteromedial, Posterior, Posterolateral, Lateral and Anterolateral) and total values (mean of 8 values) of Star Excursion Balance Test (SEBT) for both control and fatigue group during pretest and posttest are shown in table 1. Dependent T test were used to compare pretest and posttest values of 8 reach directions in both fatigue and control group, in the fatigue group 8 directions showed significant differences (AL; t = 9.727, P = 0.000), (A; P = 0.000), (AM; P = 0.000), (M; P = 0.000), (PM; P = 0.000), (P; P = 0.000), (PL; P = 0.003), (L; P = 0.000), whereas no significant differences were found for control group. SEBT total values for both groups and SEBT scores for fatigue group are presented in figures 4 and 5 respectively. The RPE scores were significantly different between the fatigue and control group at mid part (phase 3) (2.5 ± .6 vs 10.5 ± 1.1) and end ( 2.5 ± .6 vs 19.3 ± .7). The fatigue group demonstrated increased RPE scores at every point. No differences between groups were found in the RPE scores taken at the beginning of the fatigue or rest period (2.5 ± .6 vs 2.6 ± .6) (Figure 6).

Discussion

    In this paper the main interest lied in the interaction between Group (fatigue and control) and Time (pre and post fatigue). We wanted to know whether dynamic postural control of fatigue or control group depended on or was influenced by the pre or post fatigue condition, since significantly interaction was found (P = 0.013), we can say that our main findings were that the fatigue group decreased significantly with respect to reach distance on the posttest than on the pretest and decreased significantly with respect to reach distances compared with control group in the posttest. Our overall findings demonstrated a decrease in dynamic postural control as a result of fatigue as measured by SEBT.

    A decrease in postural stability after fatigue has been found in previous studies using both central (Crowell et al. 2001; Derave et al. 1998; Lepers et al. 1997; Nardone et al. 1997; Seliga et al. 1991) and local means of fatigue (Lundin et al. 1993; Nardone et al. 1998; Sparto et al. 1997). Our protocol was designed to replicate the fatigue surfboard riders would experience during the course of a paddling action used to pass over the wave breaking section and then “catch” the wave. We feel confident that the changes in RPE scores demonstrated that our subjects were fatigued to a level representative of working at more than 100% of maximal heart rate or maximal oxygen uptake (VO2max) and that this fatigue elicited dynamic postural control during posttest.

Ratings of perceived exertion

    One potential limitation to studies of central fatigue is the ability to quantify the amount of fatigue to which the subjects are subjected. It would be difficult to compare the effect of fatigue on postural stability if the degree of fatigue varied across investigations. To rectify this, several groups, including ours, have used the Borg RPE scale in an attempt to quantify the amount of fatigue (Nardone et al. 1997; Robertson et al. 2000; Seliga et al. 1991; Wilkins et al. 2004).

    Because perceived exertion and VO2max are highly correlated, the RPE scale may be used as a substitute to determine exercise intensity (Brooks et al. 1996). Nardone et al. (1998) employed the 10-point Borg RPE scale and found that their protocol elicited perceived exertion that was classified between 5 and 7 (strong to very strong). Using the 15-point Borg scale, Seliga et al. (1991) showed perceived exertion scores increased significantly with increase in work load. The RPE values ranged from 9 to 10 during a light workload to 11 to 12 during a moderate workload to 14 to 16 during a heavy workload. They also noted that sway values were higher after exercise at higher workloads.

    Other investigators have correlated RPE with percentage of maximum heart rate reserve, percentage of ventilator threshold, or percentage of VO₂max during various exercise tasks (Mahon et al. 1997; Robertson et al. 2000). In a group of physically active males, RPE was measured during treadmill exercise, cycle exercise, and simulated ski exercise at 70%,80% and 90% VO2max across the exercise modes to 15.4 to 16 at 80% and 18 to 18.2 at 90% (Robertson et al. 2000).

    Similarly, RPE has been recorded during 10-minute graded cycle-ergometer testing in males (25.3 ± 2.0 years) in relation to ventilator threshold (Mahon et al. 1997), the RPE values were 10.2 ± 1.2 at the 5-minute mark of an exercise at 80% ventilator threshold (heart rate = 124.6 ± 14.3 beats/minute) and 15.8 ± 1.7 at the 10-minute mark of exercise at 120% ventilator threshold (heart rate = 168.9 ± 13.5 beats/minute) (Mahon et al. 1997).

    The RPE values noted in afore mentioned investigations are lower than our findings of 10.5 ± 1.1 and 19.3 ± .7 during the middle (phase 2) and end of our fatigue protocol, respectively.

    Therefore, we feel confident that, during our protocol, subjects were working at a level greater than 90% VO2max at the end of protocol, and the decrease in SEBT performance noted during the posttest was a result of their fatigue.

Fatigue and balance

    Although fatigue’s effect on balance has most often been studied using force platform systems (Goldie et al. 1989; Gosselin et al. 2004; Paul et al. 2001) or static balance tests ( Crowell et al. 2001; Susco et al. 2004; Wilkins et al. 2004), our group studied previously the effects of upper body fatigue in static balance (measure by the Romberg test) (Camps et al. 2008), it must be known that this paper is the first one to report an activity related fatiguing protocol in the upper body and dynamic postural control, since most sports are dynamic in nature we think that postural control should be assessed using dynamic test to ensure the application of results. We feel confident that SEBT do not mimics surfing action completely, because there is not surfing action performed in a single-leg stance, but it gives us a valid score of dynamic postural control which is critical for success during surfing once the individual is standing on the surf board.

    Most of the studies used a local fatiguing protocol followed either an isometric fatiguing protocol (Gribble et al. 2004; Wilkstrom et al. 2004; Yaggie and McGregor 2002), a repeated lifting protocol (Corbeil, 2003) or an isometric fatiguing protocol (Forestier et al. 2002; Huston et al. 2005; Kawakami et al. 2000; Patikas et al. 2002; Vuillerme et al. 2001; Vuillerme et al. 2002).

    Most of the previous studies (Cowell et al. 2001; Gosselin et al. 2004; Paul et al. 2001; Wilkins et al. 2004) found a decrease in balance performance after fatigue protocol, although our fatigue protocol did not include the same type of exercise, our results immediately after the end of our fatigue protocol concur with those of previous researchers with respect to balance performance. In addition the results of our previous study (Camps et al. 2008) using the same fatigue protocol and Romberg test to assess balance (static balance test) concur with our present results as well.

    The present findings that balance decrease after fatigue has been demonstrated in investigations using various methods of causing central fatigue and different measures of postural stability, using varied fatigue protocols, several authors have found decrease in postural stability as measure by stabilometry (Nardone et al. 1997; Seliga et al. 1991), Nardone et al. (1997,1998) noted significant increases in sway path in both eyes-open and eyes-closed conditions and increases in sway area in eyes-closed conditions only after a 25-minute treadmill run. In addition, a 25-minute cycle-ergometer exercise elicited a significant increase in sway path with eyes open, but to a lesser extent than after the treadmill exercise (Nardone et al. 1998). A subsequent follow-up investigation using a 25-minute uphill treadmill walk also demonstrated an increase in sway path and sway area in both visual conditions after the exercise (Nardone et al. 1997).

    Similarly, using the Equitest to measure postural stability after a 25-km run, Lepers et al. (1997) found a significant decrease in posttest postural stability for all conditions except the fixed support, eyes-open condition.

    Not all researchers of central fatigue and postural stability have demonstrated a decrease in postural stability after exercise. Contrary to our results, Derave et al. (1998) found no change in center-of-pressure velocity after a 2-hour cycle protocol, indicating that the exercise bout did not elicit decreases in postural stability. They did, however, show a significant exercise hydration status interaction posttest results demonstrated higher center-of-pressure velocities when subjects were not given fluid replacement during the exertion protocol. It should be noted that their posttest took place 20 to 30 minutes after the end of the 2-hour cycle bout, thereby allowing some recovery time before the posttest. We did not allow the subjects to drink any fluids during protocol but they drank some water 10-15 minutes before protocol.

    The factors that could potentially cause a decrease in balance performance after fatigue focus on both central and local means of fatigue. Central or whole-body fatigue, refers to a decrease in the central nervous system output to the muscles (Brooks et al. 1996) and likely has a component that includes factors responsible for the sense of effort in addition to the alterations in motor pathways (McComas 1996). Localized muscle fatigue is induced by a decrease in the metabolic substrates available for muscle contraction, such as adenosine triphosfate, creatine phosphate, and glycogen, as well as an increase in metabolites, including lactic acid, in the muscle, resulting in an inability to maintain a desired muscular force output (Rozzi et al. 2000), this accumulation of metabolites and/or infammatory substances within the muscle during activity to fatigue (i.e. lactic acid or bradykinin), have been shown to elicit increased muscle spindle static and/or dynamic sensitivity via reflex-mediated pathways from chemosensitive group III and IV aferents onto Ɣ-motoneurones (Björklund et al. 2000) what would affect one`s ability to maintain equilibrium due to an incomplete afferent information. Since our subjects performed an upper body fatigue protocol and this muscular group do not play any role in postural control measured by SEBT, we can ensure that the decrease in dynamic postural control was due to central fatigue. More in deep we agree with the conclusions shown by Abbiss et al. (2005) about models of fatigue where they argue that the increase in recruitment produce and increase in the sense of effort that produce an increase in central neural activation to produce fatigue as a part of the body’s system of defense, one possible explanation could be therefore, that our subjects suffered high levels of central neural activation as a consequence of the exhaustion achieved at the end of the fatigue protocol, this central neural activation would lead to an increase in the sense of effort that would lead to a deficient processing of the information to central level, and finally, this deficient processing of the information to central level would lead to a decrease in dynamic postural control as measured by the Star Excursion Balance Test. EMG technique should be used in future research to really investigate the contributions of local and central fatigue of our protocol.

    From an applied point of view this paper seems to make clear that the time that surfers are paddling out in the prone position in order to reach the take-off area (which can last as long as 2-3 minutes) and then the powerful strokes performed once a suitable wave approaches (about 6 seconds long) needed to give the board enough speed to be gathered up by the swell produce an accumulative amount of central fatigue which decreases dynamic balance when the wave has been caught. We feel confident that there are several factors that have not been controlled in this paper and which could have an important effect in the wave riding and the amount of fatigue achieved such as wet-cold conditions, epinephrine release, motivation and wave’s characteristics such as height of the wave’s wall and distance of breakpoint from the shore as well as currents, in our opinion this issues need to be investigated in futures research.

    Our findings show a decrease reach distance in SEBT immediately after the fatigue protocol, demonstrating that balance ability diminished. The surfboard riders should improve their paddling capacity in order to avoid or delay fatigue during wave riding. Future investigators should find a more surfboard-related test to investigate if the decrease in balance ability really affects the wave riding itself. In the other hand it would be good to use surfboard riders as subjects since they must be used to the paddling exercise and the effects can be different. Our findings suggest that during surfboard training, surfboard riders should pay more attention of paddling performance in order to avoid the effects of fatigue achieved during the paddling action on the wave riding. We suggest that trainers should include in their programs some paddling related exercise such as swimming or rowing as well as paddling muscles working out.

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revista digital · Año 14 · N° 135 | Buenos Aires, Agosto de 2009   © 1997-2009 Derechos reservados