Differential Effects of Different Warm-up Protocols on... : The Journal of Strength & Conditioning Research (original) (raw)
Introduction
Sport-specific repeated sprints can induce muscle damage (21), even in well-trained populations (33,38). Thus, prolonged decrements in sports performance are expected to be seen after an intense event (e.g., soccer, basketball, tennis, etc.), which contains repeated sprinting activities. Therefore, during specific periods where competitions are densely scheduled (e.g., more than 3 times per week), insufficient recovery from previous event may serve as a negative factor influencing the subsequent matches/competitions. For example, during a high physically and mentally demanding tennis tournament, athletes usually have to play back-to-back matches with only 1- or 2-day rest in between. Such setup does not allow tennis players to get fully recovered before the next match, and muscle damage markers such as strength, power output, muscle soreness, and creatine kinase level were kept elevated during the tournament and even up to 2 days after the tournament, because of the eccentric muscle action component of the repeated sprints during a tennis match (31).
In addition to the long-term regular training programs during off-season or in-season that prepare the athletes for the high-intensity competitions, other acute preconditioning protocols have been introduced and examined to protect against the eccentric exercise-induced muscle damage and to accelerate recovery. For example, adding a bout of nondamaging submaximal eccentric exercise before maximal eccentric exercise can attenuate the latter eccentric exercise-induced muscle damage. This phenomenon is termed as the “repeated bout effect,” and it has been well-studied since late 1980s (9). However, to induce the protective effect, some time lag is needed between the first bout and the second bout (4), which makes this strategy not necessarily a realistic practical application for tennis players or other athletic populations. Thus, preconditioning protocols that can be incorporated into the warm-up exercise would potentially benefit athletes.
Regular warm-up before intense exercise or competition is usually composed of running and possibly with some stretching exercise. However, just like the varying effects of stretching on subsequent sports performance (1,2,11,12,20,24), the potential protective effects from adding a stretching protocol for warm-up on the subsequent eccentric exercise-induced muscle damage are not consistent. For example, as one of the first studies comprehensively examined the effects of static stretching on heavy eccentric exercise-induced muscle damage markers, Johansson et al. (23) did not find preventive effect on muscle damage markers such as muscle soreness, tenderness, and force loss. In a recent investigation, Chen et al. (3) incorporated static active and dynamic active stretching before the eccentric muscle-damaging protocol and found that both active stretching protocols provided protective effect but with static active stretching showing superior effect than the dynamic active stretching.
In addition to stretching, some sport-specific nonfatiguing resistance exercises have also been incorporated into a warm-up protocol to benefit subsequent exercise performance. Numerous studies have reported superior effects over static stretching or control of having a warm-up protocol with moderate- to high-intensity dynamic exercises on subsequent neuromuscular performance (15,16,29,32) and metabolites accumulation (18). Considering these positive effects from the dynamic warm-up exercises, it would be interesting to incorporate such resistance exercises as a preconditioning bout before a bout of high-intensity repeated sprints and to examine whether such interventions could attenuate potential muscle damage. It has been reported that preconditioning low-intensity eccentric exercises on knee flexors and extensors could provide protection against subsequent eccentric exercise-induced muscle damage (26).
Therefore, the purpose of this investigation was to examine the effects of adding 2 different preconditioning protocols (dynamic active hamstring stretching vs. single leg slide hamstring curl exercise) to a regular running-based warm-up before a bout of repeated sprints on potential muscle damage markers. Both stretching and resistance exercise protocols were targeting the hamstring muscles. The single leg slide hamstring curl is a relatively high-intensity resistance exercise, which requires good core strength and balance from the subjects. The dynamic stretching protocol was used because passive static stretching is generally associated with decreased muscle performance (1,34). We expected to see that the repeated sprints can induce muscle damage in the knee flexors, even for our well-trained athletes. In addition, the regular warm-up combined with dynamic stretching (active hamstring stretching [AHS]) may provide a protective effect against the maximal sprints-induced muscle damage. However, it is unclear whether the hamstring resistance exercise could influence the subsequent sprints-induced potential muscle damage. The finding of this investigation can be especially useful for practitioners such as coaches and trainers because they may directly use a specific protocol or adjust their current preconditioning warm-up protocols for athletes who are suffering from insufficient muscle damage recovery because of the densely scheduled competitions/training.
Methods
Experimental Approach to the Problem
This study used a within-subject crossover design to examine the effects of different warm-up protocols on subsequent repeated sprints-induced muscle damage up to 2 days after the sprints, thereby identifying a potentially advantageous warm-up protocol for athletes whose performance can be negatively affected by insufficient recovery because of muscle damage and their densely scheduled competitions/training. Four separate visits to the laboratory were required to complete this investigation. After the first visit as the familiarization, the next 3 testing visits were conducted in a randomized fashion as follows: (a) regular warm-up (control); (b) regular warm-up followed by a set of supine single leg slide hamstring curl (SLC) exercise; (c) Regular warm-up followed by a set of dynamic AHS exercise. Between the testing visits, a minimum of 7 days of rest was provided. All dependent variables were measured before (PRE), immediately (POST0), 1 day (POST1), and 2 days (POST2) after the maximal repeated sprints on the subjects' dominant hamstring muscles.
Subjects
Twelve elite tennis players (10 men and 2 women; mean ± SD age = 21.6 ± 4.14 years; height = 172.9 ± 8.8 cm; and mass = 71.8 ± 15.1 kg) were recruited from the College of Kinesiology at the University of Taipei. They voluntarily participated in this investigation. All subjects were classified in the national Division 1 category, who all had a training experience of 8.0 ± 2.3 years. They trained 5–6 times a week (up to 150 minutes per session) and all competed in national level competitions. Their daily training programs were typical of the tennis training and were devoted to specific exercises and skills (i.e., agility, sprint running, plyometric drills, and quick changes in direction) at moderate to high intensities for the lower limbs. This investigation was conducted during the off-competition season. Before any experimental testing, each subject completed an informed consent and a pre-exercise health and exercise status questionnaire, which indicated no current or recent ankle-, knee-, hip-, low-back–, or hamstring muscle–related injury over the past 12 months. During the consenting process, the subjects were instructed to maintain their normal habits in terms of dietary intake, hydration status, and sleep during the investigation. Extra effort was made to conduct testing at roughly the same time of the day with the same arousal levels. In addition, they were refrained from their regular training throughout the entire investigation period and were instructed to avoid any vigorous physical activities 72 hours before each testing session. All experimental procedures for this investigation were approved by the Ethics Committee on Human Research at National Taiwan University. All subjects were informed of the risks and benefits of the study, and then gave written informed consent to participate. For subjects who were under 18 years of age, written parental consent was obtained prior to any data collection.
Procedures
Familiarization
The purpose of this visit was to familiarize the subjects with all the measurement tests, 3 warm-up protocols and the muscle-damaging repeated sprints. After the standing height and body weight measurements, the research staff determined the leg dominance by asking the subject, which foot he/she would kick a soccer ball. The subject then was instructed to lie down on a medical bed completely relaxed in the supine position. The hip flexion passive range of motion (ROM) was measured by a research staff by performing the passive straight leg raise test (PSLR). Briefly after this familiarization, the subject was instructed to lie down with the prone position, during which the measurements of muscle thickness, muscle pennation angle, and muscle stiffness tests were practiced. The last measurement testing familiarization was the isokinetic strength testing, during which the subject was instructed to sit on a dynamometer (Biodex System Pro 4; Biodex Medical Systems, Inc., Shirley, NY, USA) with the upright position. With a brief warm-up, the subjects performed 3 maximal isokinetic concentric knee flexions (angular velocity of 60°·s−1). With the conclusion of measurement testing familiarization, the subjects then were instructed to practice all 3 warm-up protocols (control, SLC, and AHS) until they could perform all protocols with the correct form. Last, the subjects performed 2 sets of 30-m maximal sprints with 60 seconds rest in between for the purpose of practicing the repeated sprints.
Experimental Visits
After a minimum of 72 hours after the familiarization, subjects returned to the laboratory for one of the 3 experimental testing sessions. During each visit, the session started with the subjects performing the regular warm-up protocol (control). Specifically, the subjects started with a 5-minute running at 60–100% of their perceived maximum speed with a series of dynamic sprint drills (high knees, heel flicks, and walking lunges). After the run, a 5-minute rest was provided for the subjects with the sitting position. Instead of the 5-minute rest, the SLC and AHS protocols contained the following exercise procedures:
Single Leg Slide Hamstring Curl
The subject lay on the floor in the supine position and with both arms by his/her side. With one of the heels placed on a slide board on the floor, the subject then flexed the knee, simultaneously extended the hip to push the pelvis off the ground, to the end of the range of motion. With 1-second pause at the top, the subject slid the foot back to the starting position with controlled manner. During the action, the other leg was kept straight all the time. The subjects performed this exercise on each leg for 12 repetitions (Figure 1).
The exercise of single leg slide hamstring curl (SLC).
Active Hamstring Stretching
During the active hamstring stretching, with 1 foot standing with the upright position, the subject actively swang the other leg forward to the end of the range of motion, and then dropped the leg back to the starting position with the controlled manner. During the swings, the knee was always kept extended. Twelve stretched were performed on each leg. The first 6 stretches were performed slowly, and then the last 6 stretches were performed as quickly and powerfully as possible without bouncing (Figure 2).
The active dynamic stretching of hamstrings (AHS).
After the warm-up protocol, baseline (PRE) measurements for dependent variables were conducted with same order (hip flexion passive ROM, muscle thickness, muscle stiffness, muscle pennation angle, and concentric knee flexion isokinetic strength) as from the familiarization visit, followed by the repeated sprints. Specifically, 12 sets of 30-m maximal repeated sprints were performed by the subjects, with a 10-m acceleration and a 15-m deceleration for each sprint. The rest interval between consecutive sprints was 60 seconds. Immediately (POST0), 24 hours (POST1), and 48 hours (POST2) after the sprinting exercise, dependent variables were measured again with the same order and manner as they were measured at the baseline.
Measurements for Dependent Variables
Hip Flexion Passive Range Of Motion
The PSLR test was used to measure the hip flexion passive ROM. With the subjects lying down on a medical bed completely relaxed in the supine position. Two Velcro straps were used to secure the subject's nondominant leg (applied over the shin) and hips (applied over both anterosuperior iliac spines). With an inclinometer (Digital Inclinometer, Model No. A800; JIN-BOMB, Inc., Kaohsiung, Taiwan) placed on the dominant knee cap, a research staff grasped the ankle of the subject's leg and raised it slowly to the point that the subject first felt tension or slight stretch from the hamstring muscle. The value from the inclinometer was then recorded as the hip flexion passive ROM. To ensure consistency of this measurement, the location where the inclinometer was placed on was marked, and every time the researcher placed one end of the inclinometer on the mark to perform the measurement. In addition, extra care was taken to ensure that the subject's nondominant leg and pelvis were secured to the table with individual straps, and the dominant knee was kept straight all the time during this procedure. At least 3 trials with 15-second rest between trials were performed to establish the hip flexion passive ROM. If the values from any 2 trials differed more than 2°, extra trials would be conducted. The average of the 3 closest trials was calculated and recorded as the hip flexion passive ROM.
Muscle Thickness, Pennation Angle, and Muscle Stiffness
Muscle thickness and pennation angle were determined from ultrasound images taken along the longitudinal axis of the muscle belly of the long head of the biceps femoris (BF) muscle using a 2-dimensional, B-mode ultrasound equipment with a 7.5-MHz linear probe (Siemens ACUSON S2000; Siemens Healthcare, Erlangen, Germany). The images were then analyzed digitally offline. With the subjects lying with a prone position with their lower limbs relaxed, the probe was placed on the subject's dominant leg at the halfway point between the ischial tuberosity and the knee joint fold, along the line of the BF. The muscle thickness was quantified as the mean of the vertical distances delimited by superficial and deep aponeuroses measured at both image extremities. The pennation angle was calculated as the acute angle formed between the deep aponeurosis and the muscle fascicle.
Muscle stiffness was measured in real time based on the acoustic radiation force impulse (ARFI) technique. Using the ARFI-based elastography examination, mode to measure the shear wave velocity (SWV, m·s−1) provides an indicator of muscle stiffness of the BF, based on the significant positive correlation between the SWV and the mean muscle stiffness (37). The ARFI measurement was performed with the same ultrasound system (Siemens ACUSON S2000; Siemens Healthcare) because the muscle thickness was measured. The probe was held over the BF, parallel to the long axis of the muscle, and to obtain a valid SWV measurement. For all muscle thickness, pennation angle, and the muscle stiffness measurements, at least 3 measurement trials were taken, and the average of the 3 closest trials was calculated and recorded.
Isokinetic Knee Flexion Concentric Peak Torque
The subject sat with a comfortable position on the dynamometer. The mechanical axis of the dynamometer was aligned with the lateral epicondyle of the knee. The trunk, the waist, the thigh, and the chest were strapped with belts to minimize extraneous body movements. The range of motion of the dominant knee was set before the strength testing. The subjects performed a standardized warm-up composed of 3 submaximal (50% of perceived maximal effort) concentric contractions at the designated angular speed before each test. After a 2-minute rest, they were asked to perform 3 maximal concentric knee flexion contractions at the angular speed of 60°·s−1, and the concentric peak torque values were then recorded. A 45-second rest period was provided between consecutive maximal contractions. The highest peak torque of the 3 maximal contractions was selected for data analysis.
Statistical Analyses
Mean ± SD was used to describe all dependent variables. To examine the potential changes of each variable over time among different protocols, separate 2-way repeated measures (time [PRE, POST0, POST1, and POST2] × protocol [control, SLC, and AHS]) analyses of variance (ANOVAs) were performed. Follow-up statistical tests included 1-way repeated-measures ANOVAs and pairwise comparisons with Bonferroni adjustments. A priori power analyses (G*Power 3.1.9.2) (17) indicated that a sample size of 12 subjects resulted in statistical power values of 0.81 or greater for all the dependent variables. All statistical tests were conducted using IBM SPSS Statistics 24.0 (IBM Corp., Armonk, NY, USA), with alpha set at p ≤ 0.05. Effect sizes Cohen's d (10) and 95% confidence intervals (CIs) (13) were calculated for each pairwise comparison.
Results
Test-Retest Reliability
The test-retest reliability for the all dependent variables at PRE among all experimental visits (visits 2–4) was good, with the minimum intraclass correlation coefficient model 3, 1 (ICC 3, 1) (36) value of 0.83. In addition, all dependent variable PRE values were not significantly different among visits (Table 1). Table 2 shows the mean values and _SD_s for hip flexion passive ROM, hamstrings muscle thickness, muscle stiffness, pennation angle, and knee flexion concentric peak torque.
Intraclass correlation coefficient model 3, 1 and SEM for baseline (PRE) values of hip flexion passive range of motion (ROM), muscle stiffness, muscle thickness, pennation angle, and knee flexion concentric peak torque among 3 experimental visits.*
Mean ± SD before (PRE), immediately (POST0), 1 day (POST1), and 2 days after (POST2) the repeated sprints for hip flexion passive range of motion (ROM), muscle stiffness, muscle thickness, pennation angle, and knee flexion concentric peak torque.*
Hip Flexion Passive Range Of Motion and Muscle Stiffness
For hip flexion passive ROM, the results from the 2-way repeated-measures ANOVA indicated that there was no 2-way interaction, however, there was a main effect for time (p < 0.001). When collapsed across protocol, the follow-up pairwise comparisons showed that there were significant decrements from PRE to POST1 (p = 0.001, Cohen's d = 1.34, 95% CI = [2.840–9.786]) and from POST0 to POST1 (p = 0.002, Cohen's d = 1.07, 95% CI = [2.048–8.413]) (Figure 3A).
Hip flexion passive range of motion (A) and muscle stiffness (B) before (PRE), immediately after (POST0), 1 day after (POST1), and 2 days after (POST2) the repeated sprints; (A) is demonstrating the combined mean values across 3 protocols (control, SLC, and AHS). *Significant difference between different time points for combined mean values (p ≤ 0.05). Solid line with round dots: regular warm-up (control); short dash line with square dots: regular warm-up with a set of supine slide single leg curl exercise (SLC); long dash line with triangle dots: regular warm-up with a set of active hamstrings stretching (AHS). #Significant difference between different time points for control (p ≤ 0.05); $significant difference between different time points for SLC (p ≤ 0.05); %significant difference between different time points for AHS (p ≤ 0.05); and &significant difference between different protocols.
The 2-way repeated-measures ANOVA detected that there was a significant time × protocol interaction (p = 0.035) for muscle stiffness. Therefore, the follow-up analyses (1-way repeated-measures ANOVAs) were conducted to examine the changes of muscle stiffness through time for each protocol and to compare the muscle stiffness values among different protocols for each time point. The pairwise comparisons showed that muscle stiffness increased from PRE to POST0 (p = 0.006, Cohen's d = 0.87, 95% CI = [−0.559 to −0.091]), from PRE to POST1 (p < 0.001, Cohen's d = 1.67, 95% CI = [−0.885 to −0.282]), from PRE to POST2 (p = 0.002, Cohen's d = 1.88, 95% CI = [−1.028 to −0.234]), from POST0 to POST1 (p = 0.008, Cohen's d = 1.01, 95% CI = [−0.454 to −0.063]), and from POST0 to POST2 (p = 0.024, Cohen's d = 1.21, 95% CI = [−0.576 to −0.036]) for control; from PRE to POST0 (p = 0.005, Cohen's d = 1.13, 95% CI = [−0.814 to −0.139]), from PRE to POST1 (p = 0.003, Cohen's d = 1.95, 95% CI = [−1.212 to −0.245]), and from PRE to POST2 (p = 0.044, Cohen's d = 0.75, 95% CI = [−0.747 to −0.008]) for SLC; and from PRE to POST0 (p = 0.001, Cohen's d = 0.72, 95% CI = [−0.401 to −0.149]) and from PRE to POST1 (p = 0.018, Cohen's d = 0.99, 95% CI = [−0.740 to −0.060]) for AHS. In addition, at POST2, significant difference (p = 0.021) was found among 3 protocols, with the muscle stiffness significantly lower for AHS than that for control (p = 0.009, Cohen's d = 1.35, 95% CI = [0.107–0.722]) (Figure 3B).
Muscle Thickness and Pennation Angle
For muscle thickness, the results from the 2-way repeated-measures ANOVA indicated that there was significant interaction (p < 0.001). The follow-up analyses showed that muscle thickness increased from PRE to POST1 (p = 0.030, Cohen's d = 0.81, 95% CI = [−4.391 to −0.192]) for control; from PRE to POST0 (p = 0.024, Cohen's d = 0.46, 95% CI = [−3.127 to −0.19]), from PRE to POST1 (p < 0.001, Cohen's d = 1.02, 95% CI = [−4.941 to −1.876]), from PRE to POST2 (p < 0.001, Cohen's d = 1.28, 95% CI = [−5.985 to −2.232]), and from POST0 to POST1 (p = 0.042, Cohen's d = 0.53, 95% CI = [−3.451 to −0.049]) for SLC; and from PRE to POST0 (p = 0.001, Cohen's d = 0.68, 95% CI = [−2.933 to −0.800]), from PRE to POST1 (p < 0.001, Cohen's d = 1.27, 95% CI = [−4.443 to −2.307]), and from POST0 to POST1 (p = 0.001, Cohen's d = 0.54, 95% CI = [−2.324 to −0.693]) but significantly decreased from POST1 to POST2 (p = 0.01, Cohen's d = 1.07, 95% CI = [0.701–5.633]) for AHS. In addition, at POST2, muscle thickness was significantly different among all 3 protocols (p = 0.006), with the values significantly higher for SLC than that for control (p = 0.025, Cohen's d = 1.02, 95% CI = [0.328–5.105]) and AHS (p = 0.027, Cohen's d = 1.29, 95% CI = [0.433–7.333]) (Figure 4A).
Muscle thickness (A) and pennation angle (B) before (PRE), immediately after (POST0), 1 day after (POST1), and 2 days after (POST2) the repeated sprints. Solid line with round dots: regular warm-up (control); short dash line with square dots: regular warm-up with a set of supine slide single leg curl exercise (SLC); long dash line with triangle dots: regular warm-up with a set of active hamstrings stretching (AHS). #Significant difference between different time points for control (p ≤ 0.05); $significant difference between different time points for SLC (p ≤ 0.05); %significant difference between different time points for AHS (p ≤ 0.05); and &significant difference between different protocols.
The 2-way repeated-measures ANOVA indicated a significant interaction (p = 0.018) for muscle pennation angle. The follow-up analyses showed significant differences among all time points for all 3 protocols but not significantly different between POST1 and POST2 for AHS. In addition, there was a trend for significance among 3 protocols (p = 0.054) at POST2 (Figure 4B).
Knee Flexion Isokinetic Concentric Strength
For concentric peak torque, the results from the 2-way repeated-measures ANOVA indicated that there was significant interaction (p < 0.001). The follow-up analyses showed that the concentric peak torque decreased from PRE to POST0, from PRE to POST1, and from PRE to POST2 for all 3 protocols. However, significant increments from POST0 to POST2 (p = 0.002, Cohen's d = 1.03, 95% CI = [−27.312 to −6.605]) and from POST1 to POST2 (p = 0.013, Cohen's d = 0.87, 95% CI = [−26.091 to −2.726]) were only found for SLC. In addition, the concentric peak torque was significantly different among 3 protocols at POST0, POST1, and POST2, with greater peak torque for AHS than those for control and SLC (Figure 5).
Knee flexion concentric peak torque before (PRE), immediately after (POST0), 1 day after (POST1), and 2 days after (POST2) the repeated sprints. Solid line with round dots: regular warm-up (control); short dash line with square dots: regular warm-up with a set of supine slide single leg curl exercise (SLC); long dash line with triangle dots: regular warm-up with a set of active hamstrings stretching (AHS). #Significant difference between different time points for control (p ≤ 0.05); $significant difference between different time points for SLC (p ≤ 0.05); %significant difference between different time points for AHS (p ≤ 0.05); and &significant difference between different protocols.
Discussion
The purpose of this investigation was to examine the effects of different warm-up interventions (control vs. SLC vs. AHS) on the subsequent maximal repeated sprints-induced potential muscle damage. Based on our results, 12 sets of 30-m sprints induced hamstring muscle damage after all 3 interventions. Specifically, the prolonged depression in the hip flexion passive ROM and the knee flexion isokinetic strength (35), along with the elevated muscle thickness, the pennation angle (30), and the muscle stiffness (22) after the sprints have confirmed our expectation. Importantly, even for well-trained athletes who are traditionally believed to be less susceptible to eccentric exercise-induced muscle damage, the repeated sprints still caused muscle damage, which was in agreement with the report from Verma et al. (33).
When examined the hip flexion flexibility, no protocol effect was found, and the combined passive ROM value reached the lowest point 1 day after the sprints. This phenomenon can be explained at least partially by the accompanied muscle stiffness responses. Specifically, muscle stiffness values for all 3 protocols significantly increased from PRE to POST and kept increasing to POST1, contributing to the lowest passive ROM at that time point. However, at POST2, the muscle stiffness value was not different from PRE for the AHS protocol, and it was significantly less than that for the control, indicating that the AHS warm-up protocol imposed a superior effect in muscle stiffness recovery than the control (Figure 3). Regarding the increased muscle thickness and pennation angle, it is likely due to the swollen muscle (8) after the sprints. Different from the responses of the control and AHS warm-up protocols, the muscle thickness value peaked at POST2 for the SLC, and it was significantly greater than those for the other 2 protocols (Figure 4). Thus, adding a set of SLC to the regular warm-up exacerbated the sprints-induced muscle damage. Last, as one of the most important performance variables, the responses of the knee flexion strength were different among 3 warm-up protocols; although the isokinetic strength did not fully recover at POST2 for all 3 protocols, significant less strength decrement was observed for AHS than those for control and SLC immediately, 1 day, and 2 days after the sprints (Figure 5). Thus, a novel finding of this study was that adding a set of dynamic AHS to a regular running-based warm-up before the sprints alleviated the responses of some muscle damage markers and provided faster recovery than other warm-up protocols did. However, the effects of SLC warm-up protocol seemed more negative, at least did not provide protection against the sprints-induced muscle damage.
Previous literature has reported that low-intensity (varied between 10 and 40% of maximal voluntary isometric contraction) preconditioning eccentric exercise can attenuate subsequent maximal or submaximal eccentric exercise-induced muscle damage and accelerate the recovery (5–7,25,26). This protective effect has been attributed to several different mechanisms, including neural, mechanical, and cellular adaptations (28). In addition, remodeling of extracellular matrix can also play a role (27). However, as mentioned previously, the repeated bout effect requires some time lag between the first and second bout (4). Therefore, unlike the previous experiments during which the researchers delivered the damaging protocols at least 2 days after the preconditioning eccentric exercise, we had our subjects perform the repeated sprints right after the preconditioning exercises (SLC and AHS). As far as we know, a limited number of studies have examined the influences of preconditioning warm-up protocol on subsequent exercise-induced muscle damage. Johansson et al. (23) did not find preventive effect from adding static stretching on subsequent responses of muscle damage markers. Recently, Chen et al. (3) examined 2 types of active stretching (static vs. dynamic) protocols on subsequent eccentric exercise-induced muscle damage. Interestingly, both active stretching protocols provided protective effect but with static active stretching showing superior effect than the dynamic active stretching. It is worth mentioning that direct comparisons between our results and those from previous studies may not be appropriate, considering the different training statuses of subjects', as well as the different muscle-damaging protocols. Regardless, 12 repetitions of AHS on each thigh were enough to attenuate the repeated sprints-induced muscle damage. Thus, the protection from adding a set of AHS was effective immediately, even for the highly trained athletes.
Unlike the AHS, adding a set of SLC seemed to exacerbate the sprints-induced muscle damage. Evans et al. (14) examined the effects of actively vs. passively increasing muscle temperature (warm-up) on subsequent eccentric exercise-induced muscle damage and found that the active warm-up nonfatiguing protocol (elbow flexion exercise) increased biceps muscle temperature by 1° C but exhibited a greater circumferential increase than controls did after the muscle-damaging protocol. The authors (14) attributed this to active exercise-induced higher myotatic feedback loop activation and increased stiffness, which might have limited fiber elongation, thereby increasing the chance of fiber strain damage during eccentric exercise (19). In the current investigation, although the SLC exercise was only performed for 12 repetitions for each leg, considering its high-intensity nature (requiring high level of muscle activity for the hamstring muscles [75–80% of the maximal electromyographic amplitude] (39)), it is possible that the SLC protocol increased muscle temperature, thus, to impose a negative effect by exacerbating the sprints-induced muscle damage. However, during the dynamic hamstring stretches, knee flexor muscles remained passive. Thus, the hamstring muscle temperature was not likely to increase after the AHS warm-up protocol. Unfortunately, muscle temperature was not recorded in the current investigation, which prevented us from further narrowing down the exact physiologic mechanisms.
With the novel findings, this investigation, however, does have some worth-mentioning limitations. First and foremost, when interpreting the results of the current investigation, it is important to mention that the sprints performed in the current investigation did not exactly mimic the sprints during a tennis match. Indeed, shorter-distanced sprints are more likely be used by athletes in competitions. Second, we are not able to provide more specific details regarding the physiologic mechanisms associated with the AHS warm-up–induced protective effect against muscle damage. Because the sprints were scheduled immediately after the warm-up, it was likely that neural factors might have played the major role. Thus, future research should focus on this direction by using other variables such as myoelectric activity and mechanical activity of muscle fibers. Last, unlike most muscle damage–related research studies, our data only covered the time points up to 48 hours after the damaging protocol. The exact time spans that all the muscle damage markers returned to the baseline are unknown. Therefore, when interpreting data from this study, it is very important to mention the exact time points recorded in the current investigation.
In conclusion, adding a set of active dynamic stretching to a regular running-based warm-up protocol before repeated sprints has superior effect in attenuating sprints-induced muscle damage and accelerating the recovery than regular warm-up exercise only (control) and the warm-up with SLC. The exact physiologic mechanisms relating to the protection require further investigation. In addition, it is possible that including a bout of resistance exercise in a regular warm-up protocol may exacerbate the recovery from the damaged muscle.
Practical Applications
It is common to hear athletes (e.g., tennis players during a tournament) complaining how “fatigued” they are when they have densely scheduled matches or back-to-back competitions. This “fatigue” may include the component of high-intensity competition-induced muscle damage, which does not go away quickly and easily. Without a sufficient recovery, sports performance in the upcoming competitions can be impaired. Even worse, injuries can occur as well. Although some coaches and trainers let their athletes perform active dynamic stretching before competition, other may incorporate different warm-up protocols such as nonfatiguing resistance exercises. Therefore, the current investigation suggests that coaches and trainers incorporate dynamic stretching into their athletes' regular warm-up protocols to help facilitate the recovery from high-intensity sprints-induced muscle damage.
Acknowledgments
The authors declare no personal or financial relationships with companies or manufacturers who may benefit from the results of the present study. The results from this study do not constitute endorsement of the product by the authors or the NSCA.
References
1. Behm DG, Blazevich AJ, Kay AD, McHugh M. Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: A systematic review. Appl Physiol Nutr Metab 41: 1–11, 2016.
2. Behm DG, Chaouachi A. A review of the acute effects of static and dynamic stretching on performance. Eur J Appl Physiol 111: 2633–2651, 2011.
3. Chen CH, Chen TC, Jan MH, Lin JJ. Acute effects of static active or dynamic active stretching on eccentric-exercise-induced hamstring muscle damage. Int J Sports Physiol Perform 10: 346–352, 2015.
4. Chen TC, Chen HL, Lin MJ, Chen CH, Pearce AJ, Nosaka K. Effect of two maximal isometric contractions on eccentric exercise-induced muscle damage of the elbow flexors. Eur J Appl Physiol 113: 1545–1554, 2013.
5. Chen TC, Chen HL, Lin MJ, Wu CJ, Nosaka K. Potent protective effect conferred by four bouts of low-intensity eccentric exercise. Med Sci Sports Exerc 42: 1004–1012, 2010.
6. Chen TC, Chen HL, Pearce AJ, Nosaka K. Attenuation of eccentric exercise-induced muscle damage by preconditioning exercises. Med Sci Sports Exerc 44: 2090–2098, 2012.
7. Chen TC, Tseng WC, Huang GL, Chen HL, Tseng KW, Nosaka K. Low-intensity eccentric contractions attenuate muscle damage induced by subsequent maximal eccentric exercise of the knee extensors in the elderly. Eur J Appl Physiol 113: 1005–1015, 2013.
8. Clarkson PM, Nosaka K, Braun B. Muscle function after exercise-induced muscle damage and rapid adaptation. Med Sci Sport Exer 24: 512–520, 1992.
9. Clarkson PM, Tremblay I. Exercise-induced muscle damage, repair, and adaptation in humans. J Appl Physiol 65: 1–6, 1988.
10. Cohen JA. Power primer. Psychol Bull 112: 155–159, 1992.
11. Costa PB, Herda TJ, Herda AA, Cramer JT. Effects of dynamic stretching on strength, muscle imbalance, and muscle activation. Med Sci Sports Exerc 46: 586–593, 2014.
12. Costa PB, Ryan ED, Herda TJ, Walter AA, DeFreitas JM, Stout JR, Cramer JT. Acute effects of static stretching on peak torque and the hamstrings-to-quadriceps conventional and functional ratios. Scand J Med Sci Sports 23: 38–45, 2013.
13. Cumming G, Finch SA. Primer on the understanding, use, and calculation of confidence intervals that are based on central and noncentral distributions. Educ Psychol Meas 61: 532–574, 2001.
14. Evans RK, Knight KL, Draper DO, Parcell AC. Effects of warm-up before eccentric exercise on indirect markers of muscle damage. Med Sci Sports Exerc 34: 1892–1899, 2002.
15. Faigenbaum AD, Bellucci M, Bernieri A, Bakker B, Hoorens K. Acute effects of different warm-up protocols on fitness performance in children. J Strength Cond Res 19: 376–381, 2005.
16. Faigenbaum AD, McFarland JE, Schwerdtman JA, Ratamess NA, Kang J, Hoffman JR. Dynamic warm-up protocols, with and without a weighted vest, and fitness performance in high school female athletes. J Athl Train 41: 357–363, 2006.
17. Faul F, Erdfelder E, Lang AG, Buchner A. G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods 39: 175–191, 2007.
18. Gray SC, Devito G, Nimmo MA. Effect of active warm-up on metabolism prior to and during intense dynamic exercise. Med Sci Sports Exerc 34: 2091–2096, 2002.
19. Hardy L, Lye R, Heathcote A. Active versus passive warm up regimes and flexibility. Carnegie Res Pap 1: 23–30, 1983.
20. Herda TJ, Herda ND, Costa PB, Walter-Herda AA, Valdez AM, Cramer JT. The effects of dynamic stretching on the passive properties of the muscle-tendon unit. J Sports Sci 31: 479–487, 2013.
21. Howatson G, Milak A. Exercise-induced muscle damage following a bout of sport specific repeated sprints. J Strength Cond Res 23: 2419–2424, 2009.
22. Howell JN, Chleboun G, Conatser R. Muscle stiffness, strength loss, swelling and soreness following exercise-induced injury in humans. J Physiol 464: 183–196, 1993.
23. Johansson PH, Lindstrom L, Sundelin G, Lindstrom B. The effects of preexercise stretching on muscular soreness, tenderness and force loss following heavy eccentric exercise. Scand J Med Sci Sports 9: 219–225, 1999.
24. Kay AD, Blazevich AJ. Effect of acute static stretch on maximal muscle performance: A systematic review. Med Sci Sports Exerc 44: 154–164, 2012.
25. Lavender AP, Nosaka K. A light load eccentric exercise confers protection against a subsequent bout of more demanding eccentric exercise. J Sci Med Sport 11: 291–298, 2008.
26. Lin MJ, Chen TC, Chen HL, Wu BH, Nosaka K. Low-intensity eccentric contractions of the knee extensors and flexors protect against muscle damage. Appl Physiol Nutr Metab 40: 1004–1011, 2015.
27. Mackey AL, Brandstetter S, Schjerling P, Bojsen-Moller J, Qvortrup K, Pedersen MM, Doessing S, Kjaer M, Magnusson SP, Langberg H. Sequenced response of extracellular matrix deadhesion and fibrotic regulators after muscle damage is involved in protection against future injury in human skeletal muscle. Faseb J 25: 1943–1959, 2011.
28. McHugh MP. Recent advances in the understanding of the repeated bout effect: The protective effect against muscle damage from a single bout of eccentric exercise. Scand J Med Sci Sports 13: 88–97, 2003.
29. Needham RA, Morse CI, Degens H. The acute effect of different warm-up protocols on anaerobic performance in elite youth soccer players. J Strength Cond Res 23: 2614–2620, 2009.
30. Nosaka K, Clarkson PM. Changes in indicators of inflammation after eccentric exercise of the elbow flexors. Med Sci Sports Exerc 28: 953–961, 1996.
31. Ojala T, Häkkinen K. Effects of the tennis tournament on players' physical performance, hormonal responses, muscle damage and recovery. J Sports Sci Med 12: 240–248, 2013.
32. Thompsen AG, Kackley T, Palumbo MA, Faigenbaum AD. Acute effects of different warm-up protocols with and without a weighted vest on jumping performance in athletic women. J Strength Cond Res 21: 52–56, 2007.
33. Verma S, Moiz JA, Shareef MY, Husain ME. Physical performance and markers of muscle damage following sport-specific sprints in male collegiate soccer players: Repeated bout effect. J Sports Med Phys Fitness 56: 765–774, 2016.
34. Walsh GS. Effect of static and dynamic muscle stretching as part of warm up procedures on knee joint proprioception and strength. Hum Mov Sci 55: 189–195, 2017.
35. Warren GL, Lowe DA, Armstrong RB. Measurement tools used in the study of eccentric contraction-induced injury. Sports Med 27: 43–59, 1999.
36. Weir JP. Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res 19: 231–240, 2005.
37. Yavuz A, Bora A, Bulut MD, Batur A, Milanlioglu A, Goya C, Andic C. Acoustic radiation force impulse (ARFI) elastography quantification of muscle stiffness over a course of gradual isometric contractions: A preliminary study. Med Ultrason 17: 49–57, 2015.
38. Ye X, Beck TW, Wages NP. Reduced susceptibility to eccentric exercise-induced muscle damage in resistance-trained men is not linked to resistance training-related neural adaptations. Biol Sport 32: 199–205, 2015.
39. Zebis MK, Skotte J, Andersen CH, Mortensen P, Petersen HH, Viskaer TC, Jensen TL, Bencke J, Andersen LL. Kettlebell swing targets semitendinosus and supine leg curl targets biceps femoris: An EMG study with rehabilitation implications. Br J Sports Med 47: 1192–1198, 2013.
Keywords:
preconditioning; eccentric exercise; flexibility; muscle thickness; strength
© 2017 National Strength and Conditioning Association