Several sports are associated with a large amount of repetitive maximal effort jumps during competition or during training. For example, during an elite volleyball match, approximately 200 vertical jumps are performed (20). During a basketball match, approximately 50 vertical jumps (14) and 105 sprints (13) are performed. In addition to the high impact during competition, eccentric training or plyometric training is included in the daily training regime of athletes, to increase muscle strength and power, and to increase the power of explosive movements (12). However, these kinds of exercises are associated with a high impact on skeletal muscle, known to produce muscle damage and delayed onset muscle soreness (DOMS). The physiological responses to muscle soreness resulting from eccentric muscular contractions include a decline in muscular strength, a reduction in flexibility, an increase in muscle stiffness, and an increase in damage markers in the blood (7,5).
These facts reflect a high need for recovery strategies, but there is little information about the most effective method of recovery from DOMS. Several recovery methods have been suggested in the past years, including cooling/hydrotherapy, compression, active recovery, massage, or water immersion etc. (4,1). Some of these factors might be combined during aqua exercise. The effects and physical properties of water, such as density, hydrostatic pressure, and buoyancy might be highly useful resources for recovery, when used as a counterbalance to gravity, as a compressor, as a thermal conductor, or as a resistance (23). The counterbalance to gravity might be used for the reduction of further impacts or eccentric contractions during active recovery, as the movement in the water is only concentric. Thus, aquatic exercise might enhance circulation, while causing minimal additional damage. The compression might be used to limit the formation of edema, to increase the diffusion of waste products or to increase the blood flow. The physical properties as a thermal conductor might be used for cold/warm water immersions. The resistance of water might induce mild massaging effects and might therefore increase the lymphatic flow, while moving in the water (23). According to this, aqua exercise might be an effective method of recovery from muscle damaging exercise.
According to the aforementioned data, the aim of this study was to investigate the effects of passive recovery (P) vs. aqua cycling (AC) on isometric and dynamic strength, markers of muscle damage, DOMS, and the persons perceived physical state (PEPS) after 300 countermovement jumps (CMJs). We hypothesized that AC enhances recovery of isometric and dynamic strength, DOMS, and the PEPS after 300 CMJs compared with P.
Experimental Approach to the Problem
To test the hypothesis, we used a randomized controlled trail. Participants completed 300 maximal effort CMJs (1 jump every 8 seconds). Afterward, they were randomly assigned to either a passive recovery group (P) or an AC group, which performed 30 minutes of low-intensity cycling in a pool. Before, directly after the 300 CMJs, directly after the recovery session, and up to 72 hours post, maximal isometric voluntary contraction (MVC) and dynamic strength of leg extensor muscles, creatine kinase (CK), lactate dehydrogenase (LDH), and myoglobin were measured. Furthermore, questionnaires on DOMS (visual analog scale [VAS]) and the PEPS were completed. The exact time scale and the time points of measurements are shown in Figure 1.
During the baseline period (60 minutes), the first blood sample was taken, performance tests were conducted, and questionnaires were filled out. In the preparation period (45 minutes), subjects were prepared for the biomechanical analysis of the jumps (sticking of markers etc.) which were performed directly afterward. After the 300 CMJs, the same measurements as during the baseline were performed. After a 45-minute rest period, athletes either recovered passive or active on the aqua bike for 30 minutes. Sixty minutes after, the last performance tests of the first day were conducted (Figure 1).
Twenty healthy male sport students (mean ± SD, age: 24.4 ± 2.2 years, age range: 19-27 years, weight: 81.6 ± 7.6 kg, height: 184.9 ± 5.9 cm) volunteered and gave written informed consent to participate in this study. All 20 participants completed the study. The study protocol conforms to the Code of Ethics of the World Medical Association and was approved by the Ethical Committee of the university. All subjects were informed of the benefits and risks of the investigation before signing the institutionally approved informed consent document to participate in the study.
Jumping Height During 300 Countermovement Jumps
All participants performed 300 CMJs without arm motion (hands on hips) on 2 synchronized piezo-type force platforms (model 9287, 1,080 Hz, 0.9 × 0.6 m, 8 channel amplifier type 9865; Kistler Instrumente AG, Winterthur, Switzerland). Countermovement jumps were performed every 8 seconds at a prearranged acoustic signal. Each single jump was recorded. The eight-second interval was used to reset the force platform. The participants were regularly encouraged by the research stuff to jump as high as possible. The jumping height of the participants was determined by the flight height of the center of mass of the body and was calculated by equation 1:
The vertical component of the ground reaction force of each force platform was summated and reduced by body weight to . The total integral of was spanned from the beginning of counteracting phase () to point of toe-off (). The body mass () of participants was measured, and the acceleration due to gravity () was determined.
Maximal Isometric Voluntary Contraction and Dynamic Fatigue Test
According to Goodall et al. (2008), MVC of knee extensor muscles was used as a measure of fatigue and was measured at an inner knee angle of 120° on a leg extension machine (Edition-Line; gym80 International GmbH, Gelsenkirchen, Germany), that was connected to a force sensor (KM1506; megaTron; Munich, Germany), with a measuring range of 0–5,000 N (8). Participants were asked to perform 3 MVCs (4 seconds duration). The force values were determined as the highest sliding average over a 7 milliseconds time window. The highest value of the 3 trials was recorded.
Afterward, 30% of MVC was calculated for each participant individually. For the testing of submaximal performance and its fatigue, participants were asked to perform as many repetitions as possible with the calculated weight within a range of motion of 90°–150°. For the control of the range of motion and the movement velocity, a biofeedback system was used. Concentric and eccentric phase was 1 second each. The number of repetitions was recorded.
Recovery was either passive lying in a supine position or active on an aqua bike (Aquarider; nemcomed GmbH, Teningen, Germany), each lasting 30 minutes. Aqua cycling was performed under thermoneutral conditions (31° C). While sitting on the bike, the body was immersed up to the chest. Participants were asked to perform a cadence between 65 and 75 rpm.
Creatine Kinase, Lactate Dehydrogenase, and Myoglobin
Venous blood samples were collected for the determination of CK, LDH, and myoglobin. For the investigation of acute and long-term effects of CMJs and recovery, 1 venous blood sample was taken before exercise under resting conditions (R), 1 sample directly after the 300 CMJs (post-CMJ), 1 sample directly before the recovery session (pre-Rec), and 7 samples were taken at 0 minutes (0′), 60 minutes (60′), 120 minutes (120′), 240 minutes (240′), 24 hours, 48 hours, and 72 hours after cessation of recovery (Figure 1).By the Vacutainer blood withdrawal system (Becton Dickinson), 8.5 ml of blood was collected. After storage at 7° C for ∼30 minutes for deactivation of coagulation factors, the blood samples were centrifuged for 10 minutes at 1.861 g and 4° C (Rotixa 50; Hettich Zentrifugen, Mühlheim, Germany). The serum was stored at −80° C until analysis.
Serum levels of CK (U·L−1) and LDH (U·L−1) were analyzed with an autoanalyser (ADVIA 1800, Siemens healthcare, USA) using an enzymatic-photometric method. Myoglobin (ng·mL−1) was determined using human ELISA kits (Myoglobin ELISA EIA-3955; DRG Instruments GmbH, Marburg, Germany).
Lactate and Heart Rate
Capillary samples from the earlobe were collected for lactate analysis (EBIOplus; EKF Diagnostic Sales, Magdeburg, Germany) during the 300 CMJs (after every 100th jump) and during the recovery session (after 15 and 30 minutes). Heart rate (HR) was recorded continuously during the 300 CMJs and during recovery. Rate of perceived exertion (RPE) was asked after 50 jumps each and during recovery.
Persons Perceived Physical State and Delayed Onset Muscle Soreness
Under resting conditions (R), directly after the 300 CMJs (post-CMJ), directly before and after the recovery session (pre-Rec/0′), and 60 minutes (60′), 240 minutes (240′), 24 hours, 48 hours, and 72 hours after cessation of recovery (Figure 1), a scale was used to assess the PEPS. The participants were asked to judge spontaneously to what extent 20 given adjectives coincide with their current physical feeling. Each of the 4 dimensions of the PEPS includes 5 adjectives: perceived physical energy (e.g., flabby, washed out), perceived physical fitness (e.g., well trained, strong), perceived physical flexibility (e.g., flexible, elastic), and perceived physical health (e.g., sick, injured). Subscale values of the PEPS were computed by a mean function over all items of the belonging subscale.
The rating of DOMS was assessed by sitting down on a chair from an upright posture and standing up again from this position without using the arms. The participants were then asked to rate their perceived physical pain using a 0–10 VAS at the same time points as for the PEPS scale.
Statistical analyses of the data were performed using a statistics software package (Statistica for Windows, 7.0; Statsoft, Tulsa, OK, USA). Descriptive statistics of the data are presented as mean ± SD. To assess the effect of the 2 recovery methods on the mentioned parameters, repeated-measures analysis of variance (ANOVA) with Fisher post hoc test was used. For each parameter, we reported the p-value corresponding to the main intervention effect, time effect, and intervention time. Statistical differences were considered significant for p ≤ 0.05. The average of the following jumps (0–10; 21–30; 46–55; 71–80; 96–105 etc.) was used for statistical analysis, for the comparison between both groups and for changes over time.
300 Countermovement Jumps
Changes in lactate concentration, HR, and RPE during the 300 CMJs are shown in Table 1. All parameters significantly increased over time, but no significant differences were found between both groups.
The AC group started with a jumping height of 31.5 ± 3.8 cm. After 36 jumps, participants reached their maximum jumping height of 32.1 ± 2.9 cm. Afterward, jumping height decreased, reaching a value of 27.8 ± 4.0 cm at the end. Accordingly, jumping height decreased by 13.4% from the maximum to the end. A simple linear regression from the maximum to the end of the AC group provided a coefficient of determination (R2) of 0.995, showing a linear decrease of performance (Figure 2).
The P group started with a jumping height of 29.5 ± 3.4 cm. After 54 jumps, participants reached their maximum jumping height of 30.8 ± 3.9 cm. Afterward, jumping height decreased, reaching a value of 26.3 ± 4.0 cm at the end. Accordingly, jumping height decreased by 14.6% from the maximum to the end. A simple linear regression from the maximum to the end of the P group provided a coefficient of determination (R2) of 0.996, also showing a linear decrease of performance (Figure 2).
The Pearson product-moment correlation coefficient between both groups was 0.99, and the 2-factorial repeated-measures ANOVA with Fisher-Least significant difference (LSD) post hoc test showed no significant difference between the groups.
Changes in lactate concentration, HR, and RPE before and during AC or P are shown in Table 2. During AC, HR and RPE values were significantly higher compared with passive rest.
Maximal Isometric Voluntary Contraction and Dynamic Fatigue Test
For relative MVC, overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.69), and no interaction effect (intervention time) (p = 0.97). Post hoc analysis revealed that in both conditions (AC and P), relative MVC was significantly decreased after CMJ up to 72 hours compared with before (Figure 3A). The largest decrease was present after 24 hours with 21 ± 9% (AC) and 22 ± 5% (P), respectively. Reliability of MVC was determined by the intraclass correlation coefficient (ICC) (ICC: 0.97).
For the number of repetitions with a weight according to 30% of MVC, overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.29), and no interaction effect (intervention time) (p = 0.15). Post hoc analysis revealed that in both conditions (AC and P), number of repetitions was significantly decreased after CMJ up to 24 hours compared with before (Figure 3B), and up to 72 hours in the p condition. The largest decrease was present after CMJ with 35 ± 13% (AC) and 39 ± 16% (P), respectively. Intraclass correlation coefficient for the number of repetitions was 0.86.
Myoglobin, Creatine Kinase, and Lactate Dehydrogenase
For myoglobin (coefficient of variation (CV) for intra-assay precision: 5.5%), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.23), and no interaction effect (intervention time) (p = 0.99). Post hoc analysis revealed that in both conditions (AC and P), myoglobin levels were significantly increased after CMJ up to 240′ compared with before (Figure 4A).
For CK (CV for intra-assay precision: 0.6%), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.09), and a significant interaction effect (intervention time) (p = 0.007). Post hoc analysis revealed that CK levels were significantly increased 0′ after recovery up to 72 hours compared with before in the AC condition, whereas in the P condition, CK levels were significantly increased 120′ after recovery up to 48 hours compared with before (Figure 4B).
For LDH (CV for intra-assay precision: 0.8%), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.88), and a significant interaction effect (intervention time) (p = 0.01). Post hoc analysis revealed that LDH levels were significantly increased after CMJ up to 72 hours compared with before in the AC condition, whereas in the P condition, LDH levels were significantly increased after CMJ up to 48 hours compared with before (Figure 4C).
Persons Perceived Physical State and Delayed Onset Muscle Soreness
For the rating of muscle soreness, overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.79), and no interaction effect (intervention time) (p = 0.77). Post hoc analysis revealed that in both conditions (AC and P), rating of muscle soreness was significantly increased after CMJ up to 72 hours compared with before (Figure 4D). The reliability of the VAS for the measurement of acute pain was ICC = 0.97.
For perceived physical fitness (Cronbach's alpha = 0.92), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.20), and no interaction effect (intervention time) (p = 0.33). Post hoc analysis revealed that in both conditions (AC and P), perceived physical fitness was significantly decreased after CMJ up to 72 hours compared with before (Figure 5A).
For perceived physical flexibility (Cronbach's alpha = 0.82), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.21), and no interaction effect (intervention time) (p = 0.97). Post hoc analysis revealed that in both conditions (AC and P), perceived physical flexibility was significantly decreased after CMJ up to 72 hours compared with before (Figure 5B), except for pre-Rec and 240′ for P only.
For perceived physical energy (Cronbach's alpha = 0.92), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.65), and no interaction effect (intervention time) (p = 0.51). Post hoc analysis revealed that in both conditions (AC and P), perceived physical energy was significantly decreased after CMJ up to 72 hours compared with before (Figure 5C).
For perceived physical health (Cronbach's alpha = 0.86), overall ANOVA showed a significant time effect (p < 0.001), no intervention effect (p = 0.66), and no interaction effect (intervention time) (p = 0.54). Post hoc analysis revealed that in both conditions (AC and P), perceived physical health was significantly decreased after CMJ, pre-Rec and 24 hours, 48 hours and 72 hours compared with before (Figure 5D).
This study investigated the effects of P vs. AC on performance, markers of muscle damage, muscle soreness, and the PEPS after 300 CMJs. The major findings of this study are that maximal isometric and submaximal dynamic strength showed significant decreases in both groups of up to 21% and 39%, respectively. Myoglobin, CK, and LDH significantly increased, showing different kinetics over time. Also each of the 4 dimensions of the PEPS showed significant decreases, and the VAS showed significant increases. However, no significant differences were found between both groups for any of the measured parameters.
The serum levels of CK, LDH, and myoglobin are routinely measured as indirect markers of muscle damage (3). The increase in these markers in this study may therefore be an index of cellular necrosis and tissue damage after 300 CMJs (19). Thereby postexercise levels of CK are related to the intensity of exercise and muscular strain. Also myoglobin, the oxygen-binding protein in muscle, is released into the bloodstream in increasing amounts on muscle damage (19).
Creatine kinase and myoglobin are well known for their role in muscle disruption. Creatine kinase peaks around 24–72 hours, whereas myoglobin shows a much shorter (hours) response (19), which is supported by the present results. Myoglobin showed its peak directly after recovery, whereas CK showed its peak 24 hours after. Myoglobin is approximately half the size of CK, which makes it easier to permeate the membrane. Myoglobin is released from damaged muscle directly into the bloodstream, whereas CK is released first into the lymph (19,9). The significant increases of all 3 markers after 300 CMJs clearly show the high muscular strain.
Although there was no statistical significance between AC and P for CK, LDH, and myoglobin, serum levels tended to be higher after AC. These higher increases might be explained by an increased blood flow and lymph flow during active recovery, which might lead to a faster/higher release into the bloodstream or the lymph. Furthermore, the compression and mild massaging effects of the water might have increased the blood and lymph flow additionally and therefore the diffusion of CK, myoglobin, and LDH. Another possibility for the higher damage marker levels after AC might be the aquatic exercise itself. Regardless of the low-intensity, athletes in the AC group had to perform 30 minutes of additional exercise, which produces extra force to the muscle. This additional force could have been another factor for the slightly higher levels of damage markers after AC compared with P. The present and previous studies show that there is a great interindividual variability in serum CK, which complicates the interpretation and assignment of the effects of a certain intervention. High and low responders have been suggested and the main contributors to intersubject variability include sex (22), age (18), training status (15), mode of exercise (11), and genetic factors (24). The amount of variability in damage markers of this study may have nullified significant difference between P and AC. Furthermore, we cannot exclude that the measurements of MVC and the dynamic fatigue tests also contributed to the increases of damage markers and fatigue. In particular, this might have influenced the effects over time within each group, but not the comparison between both groups, as the settings were the same for P and AC.
Despite the slightly higher levels of damage markers after AC, the rating of muscle soreness was similar in both groups. Muscle soreness showed its peak 24 hours and 48 hours after 300 CMJs, which concurs with previous literature (8). Similar to VAS, all items of the PEPS scale showed the largest decreases 24 hours and 48 hours after, again with no significant differences between groups.
The average reduction in jumping height of this study was 14%. A previous study using ∼80 CMJs with similar rest intervals showed a decrease of vertical jump height of 5.5% (16). It is known that vertical jumping–induced fatigue alters muscle properties (10,2) and, thus, the ability to generate maximum joint torques. Consequently, MVC of knee extensor muscles showed the largest decline immediately and 24 hours after exercise (21%), which is in accordance with previous studies (6). After 201 ± 69 CMJs with ∼8-s rest intervals, Pereira et al. (2009) reported a decrease in maximal voluntary isometric knee extension torque of 7% (17). After long rest intervals (∼8 seconds), fatigue was caused mainly by peripheral fatigue (reduced peak twitch torque), while using shorter rest intervals (∼6 seconds), fatigue was caused by central (reduced voluntary activation) and peripheral fatigue (17). After 100 drop jumps, Goodall et al. (2008) showed a decrease of MVC of ∼20% directly after exercise, which is similar to the present results. However, the athletes in this study showed a faster recovery pattern, compared with the present results (8). Seventy-two hours after exercise, our athletes still showed a decreased MVC of 13%, whereas in the study of Goodall et al. (2008), MVC was only decreased by ∼5% and ∼2% after 96 hours (8).
No differences in performance were found between AC and P of this study. In contrast, Takahashi et al. (2006) found no reduction in muscle power in long distance runners performing aqua exercise (walking, jogging, and jumping) after downhill running compared with passive recovery (21). Comparing serum CK levels, muscle damage might not have been as high as in this study (21). Therefore, it might be speculated that aqua exercise is only effective after mild muscle damage, or that this kind of recovery intervention needs to be repeated more frequently or should be combined with cooling to generate effects.
The results of this study showed, that a single 30-minute session of AC after 300 CMJs did not affect the recovery of muscular performance, the increase in markers of muscle damage, muscle soreness, or the PEPS compared with passive rest.
Although elite (game sport) athletes might be more familiar with large amounts of repetitive maximal effort jumps or plyometric training (both including eccentric actions) than the participants of this study, coaches and athletes should be aware that vertical jumping–induced fatigue decreases the ability to generate maximal isometric and submaximal dynamic force for more than 3 days after training. Aqua cycling was not able to attenuate these effects compared with passive rest. It needs to be proven whether AC combined with cold water immersion generates positive effects on recovery. Furthermore, the present results show that myoglobin and LDH are accurate biomarkers to determine the strain shortly after a training session, whereas CK and again LDH can be used even a day or 2 days after.
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