Running is classified as a weight bearing activity that is frequently done on hard surfaces; therefore, it can be orthopedically stressful. Most running-associated injuries are caused by the repetitive ground reaction forces incurred during foot contact, which can be 5–10 times the body weight, depending on the surface grade (3). Because of this, musculoskeletal injuries, especially associated with the lower extremities, are very common. Running in deep water has been used as an alternative training method for injured runners because the principle of specificity is not compromised, meaning that the runners can continue to run because of the less impact placed on their lower extremities without having to be concerned about another means to maintain their training status, such as cycling, which is not specific to their sport (8). Aquatic treadmill running (ATM) reduces the stressful impact from running on the ground because there is less ground impact forces compared with running on land. The mechanism by which various water exercises reduce musculoskeletal loading is that the buoyant force provided by water decreases the individual’s weight in relation to the degree of submersion and also decreases the amount of force and joint compression applied to the lower extremities (10). Water provides resistance to movement as a result of the increased viscosity and density that is associated with the environment of water (10). This resistance is equal to the amount of force exerted by the individual and varies according to the velocity and speed at which the exercise is performed (10). With this being known, the water environment allows for high levels of energy expenditure with relatively little strain on the body (4). According to Loupias and Golding (8), if ATM is performed at a high enough intensity, cardiorespiratory fitness levels can be maintained and even be improved. On the same note, a study conducted by Eyestone et al. (5) assigned trained runners into a water running, cycling, or treadmill running group and completed 6 weeks of training all at the same level of frequency, duration, and intensity. At the end of the 6 weeks, it was also found that all subjects either maintained or improved their V[Combining Dot Above]O2max, demonstrating that ATM was capable of maintaining or even improving V[Combining Dot Above]Omax (5).
Several types of water exercise, such as swimming, shallow walking, jogging, and running, and aquatic running are gaining popularity within the training realm because of its ability to improve or maintain cardiorespiratory fitness, low impact on the lower extremities, and less thermally stressful on the body (9). According to Quinn et al. (11), during exercise in the water, both maximal and exercise heart rates are lower than the rates on land by approximately 10 b⋅min−1. These differences may be attributed to the lower maximal oxygen demand and exercise environment. Water exercise is less thermally stressful because the rate of heat loss to water is greater when compared with the rate of heat loss to air (9). Heat is dissipated more easily in water, which results in the heart not having to work as hard to dissipate body heat and maintain cardiac performance (9). In a study by Michaud et al. (9), an 8-week progressive, aerobic, interval deep water run training program was conducted 3 days a week at an intensity of 63–82% on healthy sedentary individuals to assess cardiorespiratory fitness. There was a 20.1% increase in deep water running V[Combining Dot Above]O2max, suggesting that like other aerobic activities, aquatic treadmill running has the potential to produce gains in cardiorespiratory fitness when conducted at the appropriate frequency (3–5 days per week), intensity (60–90% maximal heart rate), and duration (20–60 minutes) (9). It is suggested that ATM can be an alternative means for improving or maintaining cardiorespiratory fitness in athletes and fitness enthusiasts.
Aquatic treadmill running has gained popularity because of its ability to decrease musculoskeletal impact placed on the ligaments, joints, and tendons, which is coupled with land-based exercises (14). Therefore, aquatic walking or running exercise or both could be a useful alternative to land-based exercise for injured athletes, those looking to maintain their training status, and at-risk populations. Aquatic treadmill running is increasingly being implemented by athletes as a form of supplementary training for the sole purposes of reducing the impact stresses and training for cardiovascular fitness (13). Aquatic treadmill running also reduces the musculoskeletal loading while maintaining a training stimulus and decreases the likelihood of injuries associated with overtraining (13). Athletes recovering from strenuous competitive games may maintain their training status by implementing ATM (13). In a study by Reilly et al. (12), it was demonstrated that ATM running after a series of drop jumps sped-up the recovery process, which was determined by leg strength returning to baseline levels and reduction in perceived soreness scores. These observations support the use of ATM in the days subsequent to performing stretch-shortening exercise or after strenuous competitive games (12). According to Cable (2), ATM avoids overtraining effects and maintains central training stimulus when used as an alternative training method for athletes. Also, ATM accelerates recovery from competition: When players are experiencing delayed-onset muscle soreness, ATM can promote pain-free exercise while maintaining flexibility (2). Goals for strength and conditioning coaches are to improve athletes’ performance and to decrease the likelihood of injury. These goals can both be achieved through the use of aquatic treadmill training because it has the ability to reduce musculoskeletal loading that athletes experience during the competitive season, which in turn will allow athletes to stay healthy and not become overtrained while simultaneously maintaining or possibly improving their training status (2–5,8–14). Aquatic treadmill running has been shown to decrease the musculoskeletal loading; however, the impact ATM has on various performance markers, such as force and power of athletes, has not been well-documented.
Tabata training has been implemented to improve both aerobic and anaerobic capacities simultaneously by imposing intensive stimuli on both systems (16). Methods for Tabata training are as follows: the whole exercise session is 4-minute long alternating between 20 seconds of intense exercise and 10 seconds of rest for a total of 8 rounds (16). Tabata training can be used with various training methods, such as running, cycling, and resistance training. However, to the best of our knowledge, no study has investigated Tabata training via an ATM. Commonly, ATM has been used in the orthopedic rehabilitation setting as a mode of treatment modality for injured individuals; however its effects on recreationally active subjects and performance variables including body fat percentage, force production, flexibility, and anaerobic power via an 8-week interval-training program is unknown. Therefore, the purpose of this study was to investigate the effects of an 8-week ATM Tabata interval-training program on various performance variables including body fat percentage, force production, flexibility, and anaerobic power. It was hypothesized that an 8-week ATM Tabata interval-training program would lead to improvements in all of the above-mentioned performance variables.
Experimental Approach to the Problem
The study was designed to investigate how an 8-week ATM Tabata interval-training program (independent variable) influences several performance variables, including body fat percentage, flexibility, force production, and anaerobic power (dependent variables) in recreationally active males and females. Program length was set at 8-week long because physiological results have been shown to take place over this period. Moreover, this training program was not done as an alternative or supplementary training method because of the high-intensity nature of Tabata interval training (1,16). A 2-way repeated measures analysis of variance (ANOVA) was used to analyze Pre-Post test differences over time. Paired samples t-test, when appropriate, was used to determine where differences between the groups occurred. Participants were randomized into 1 of the 2 groups: Control group (CON), which only completed Pre- and Posttesting, or Exercise group (EX), which took part in the 8-week ATM Tabata interval-training program. Pre- and Posttesting consisted of the following measurements: body fat percentage measured through the use of the BodPod, flexibility measured by completing the sit-and-reach test and with the use of a goniometer, force production measured with a 6-second vertical jump test on a force plate, and anaerobic power measured by completing a Wingate test on an electronically braked cycle ergometer. These performance variables were selected because of the importance in most athletic events. The Tabata interval-training program consisted of sprinting in chest-to-neck deep water on an ATM (HydroWorx 1200, Middletown, PA, USA). An ATM Tabata interval-training program was used because the musculoskeletal impact placed on the ligaments, tendons, and joints would be minimized, and the sprinting was considered an intense enough stimulus to maintain or possibly even increase the above-mentioned performance variables.
Overall, 25 (males = 17 and females = 8) subjects, between 19 and 24 years of age, participated in this 10-week study. Participants were recruited from the Exercise Physiology classes at The University of Akron. Age, height, and weight were recorded for all participants, as illustrated in Table 1. Participants were eligible if they had no contraindications to exercise, were injury free, and had participated in regular exercise including both cardiovascular and resistance training within the past 3 months before the study to ensure that they all had some level of baseline fitness and would not be affected significantly by the effects of delayed-onset muscle soreness. Exclusion criteria consisted of orthopedic injuries of the shoulder, hip, knee, foot, ankle, or neck or any sprains or strains in the 3 months preceding the study or both that would affect performance. Participants who missed >3 sessions were excluded. Participants were instructed to continue their daily normal activities outside the study. It was also advised that all participants maintain their current diet, exercise regiment, and refrain from using performance-enhancing supplements (creatine, caffeine, steroids, ephedrine, etc). Participants were also advised to refrain from any lower-body resistance training exercises at least 24 hours before each training session to prevent any fatigue or delayed-onset muscle soreness from affecting their performance. Before participation in the study, participants were notified about the experimental procedures and any potential risks and benefits associated with the study and signed an informed consent form. Additionally, participants completed a Physical Activity Readiness questionnaire. Participants were randomly assigned to either the CON (n = 12) group that only completed Pre- and Posttesting or EX (n = 13) group that took part in the 8-week ATM Tabata interval-training program. This study received approval from the Institutional Review Board of the Office of Research Services and Sponsored Programs at The University of Akron.
Weeks 1 and 10 consisted of Pre- and Posttesting, respectively, of the following performance variables: body fat percentage, force production, flexibility, and anaerobic power. The familiarization trial for the EX group consisted of completing 4 rounds instead of 8 of the ATM Tabata interval training. This allowed the participants to become familiar to the workout because none of them have ever experienced ATM and so that they could be instructed on the proper technique. Participants were instructed to run as they normally do with some minor changes: slight forward lean, both hands opened with fingers close together, high knee flexion, and vigorous arm and leg pumping. Testing order, established by the National Strength and Conditioning Association (NSCA) (1), was as follows: BodPod, force plate, sit and reach, goniometry, and Wingate test. The BodPod (COSMED, Chicago, IL, USA) was used to measure body fat percentage. Participants were instructed to refrain from eating or taking part in any form of physical activity 2 hours before, wear tight-fitting clothing (spandex and a swim cap for males and spandex, sports bra, and swim cap for females), remove all jewelry and piercings, and to refrain from moving during testing according to the guidelines established by the American College of Sports Medicine (ACSM) (7). Flexibility was first measured with a sit-and-reach box (Figure Finder Flex-Tester; Novel Products, Inc., Rockton, IL, USA) based on the guidelines established by the ACSM (7). Best of the 3 trials was recorded. The second flexibility test consisted of measuring hamstring flexibility of both right and left legs with a goniometer (Baseline Absolute Axis 12″ Clear Goniometer; ProMed Products Xpress, Bolingbrook, IL, USA). Participants were instructed to lie flat on their back and raise one leg at a time with a locked knee as high as possible without raising their hips or buttocks off of the table according to the guidelines established by the ACSM (7). Best of the 3 trials was recorded for each leg. A force plate (AccuPower; AMTI Force and Motion, Watertown, MA, USA) was used to measure force production. Participants performed 3 countermovement squat jumps while jumping as high as possible according to the guidelines established by the NSCA (1) during the 6-second test. Participants completed a Wingate test according to the guidelines established by the ACSM (7).
Weeks 2 through 9 consisted of a 2 times per week ATM Tabata interval-training program for the EX group. Before entering the water, heart rate of the participants was recorded, and the 9 lb (4.1 kg) weight vest (MIR Vest, San Jose, CA, USA) was placed on. Participants were required to wear a weight vest because it allowed them to sprint during ATM without bouncing up and down from the buoyant forces. The participants first completed a 5-minute warm-up in which the speed progressively increased from 4.0 to 6.0 miles⋅h−1 (0.5 miles⋅h−1 increments every 1 minute) with the front jets set at 60%. Afterward, a 3-minute rest period was implemented. After the 3-minute rest period, the Tabata interval training was initiated. Treadmill speed was set at 7.5 miles⋅h−1, and the intensity of the front jets was set at 80, 85, 90, or 95%, which was distributed equally among all joints. The Tabata interval-training program consisted of completing 20-second all-out sprints with a 10-second rest period in-between for 8 rounds. Afterward, the participants performed a 5-minute cooldown in which the speed progressively decreased from 6.0 to 4.0 miles⋅h−1 (0.5 miles⋅h−1 increments every 1 minute) with the front jets set at 60%. During each 10-second rest period, heart rate and rating of perceived exertion were recorded. Heart rate was recorded by a waterproof Polar chest strap heart rate monitoring device (Polar FT1; Power Systems, Knoxville, TN, USA). Rating of perceived exertion was assessed using the 6-20 Borg scale. During weeks 2 and 3, the front jet was at 80%, weeks 4 and 5 at 85%, weeks 6 and 7 at 90%, and weeks 8 and 9 at 95%. By progressively increasing the front jets, the Tabata interval training became more difficult to complete because of the increased resistance one has to run against. This progressive increase in the front jets required the participants to increase the speed of the pumping action of the arms and legs during ATM, which lead to an increase in heart rate (8). One session was approximately 20 minutes in length. Water height was chest-to-neck deep on all participants. Water temperature was between 26° and 28° (79–82° Fahrenheit) to allow conductive heat dissipation (3).
Pre-Post test differences over time were analyzed using a 2-way repeated measures ANOVA with SPSS V.18.0 software. The ATM Tabata interval-training program was the independent variable. Dependent variables were body fat percentage, force production, flexibility, and anaerobic power. Post hoc paired samples t-test analysis, when appropriate, was performed to determine where differences between the groups occurred. Statistical significance was set a priori at p < 0.05.
A 2-way repeated measures ANOVA revealed a significant effect of time (F = 236.13; p < 0.001) and group by time interaction (F = 1.95; p = 0.02). Paired samples t-test revealed a significant difference in the CON group from Pre- to Posttesting for mean power from the Wingate test (t = −2.20; p = 0.05), as illustrated in Figure 1. Paired samples t-test revealed a significant difference in the EX group from Pre- to Posttesting for right leg goniometry (t = −2.34; p = 0.04) and mean power from the Wingate test (t = −2.81, p = 0.02), as illustrated in Figures 2 and 1, respectively. Both the CON and EX groups significantly increased their mean power from Pre- to Posttesting; however, the EX group increased their mean power (p = 0.02) slightly more compared with the CON group (p = 0.05). A trend toward significance was revealed for body fat percentage (t = 2.14; p = 0.06) for the CON group and peak power from the Wingate test (t = −2.09; p = 0.06) for the EX group. Pre- to Posttest means and standard deviations are depicted in Table 2 for the CON and EX groups, respectively.
The purpose of this study was to investigate the effects of an 8-week ATM Tabata interval-training program on various performance variables, such as body fat percentage, force production, flexibility, and anaerobic power. It was hypothesized that an 8-week ATM Tabata interval-training program would lead to improvements in all of the above-mentioned performance variables. Body fat percentage may not have improved because it is recommended by the ACSM (7) that to have weight loss occur one must engage in 150–250 minutes of cumulative moderate-intensity exercise per week. The NSCA states that trained individuals with relatively low body fat percentage will not see reductions in body weight unless loses in lean body mass occur (1). Achieving a negative caloric balance is critical for weight loss, which is unlikely the majority of the participants achieved because they were only engaging in a 4-minute ATM Tabata interval-training program, and it was also advised that they maintain their current diet. Also, the lack of improvement in force production could have occurred because of the buoyant properties of water, increasing the length of the amortization phase. If the amortization phase is too long, the energy stored during the eccentric phase is dissipated as heat, and then the stretch reflex will not increase muscle activity during the concentric phase (1). However, the resistance to movement provided by water and the anaerobic nature of the protocol allowed participants to maintain their force production.
Flexibility may have been improved from Pre- to Posttesting because the participants were able to use the buoyant properties of water to increase their range of motion during each stride. However, buoyancy from the water was minimized by having the participants wear a 9-lb-weight (4.1 kg) vest. Simpson et al. (15) demonstrated a 7.3% increase in the sit-and-reach flexibility test after 8 weeks of deep water aerobic training. Right leg flexibility increased in the EX group from Pre- to Posttesting possibly because of the fact that this was the dominant leg for majority of the participants and their Pretest flexibility scores were lower than their left leg flexibility scores. With this being said, there was greater room for improvement from Pre- to Posttesting only in the right leg. Flexibility may not have increased during the sit-and-reach test because of the lack of flexibility in the left leg and lower back. Anaerobic power may have been improved from Pre- to Posttesting as a result of the resistance to movement provided by water. This resistance is equal to the amount of force exerted by the individual and varies according to the velocity and speed at which the exercise is performed (10). Speed remained constant during all Tabata interval-training sessions; however, when the front jets increased, this required the participants to generate more force to complete the exercise, which in turn increased the resistance to movement. According to Glass et al. (6), because of the density of the water, subjects used more anaerobic energy because of the increased challenge to the exercising muscles. Both the density of water and altered running style (different recruitment of muscle activity patterns of ATM) contribute to greater involvement of the anaerobic energy system during deep water running (6). Mean power may have increased in the CON group because of a learning curve from Pre- to Posttesting in the Wingate protocol. Also, there were no limitations on what the participants could do outside of the study in regards to their training regimen. Buoyant forces and resistance to movement, which are both found within the water environment, may be the reason for improvements seen in both flexibility and anaerobic power in terms of mean power. These results are favorable because it shows that participants who engage in an 8-week ATM Tabata interval-training program can elicit a strong enough stimulus to improve flexibility and anaerobic power in terms of mean power while simultaneously decreasing musculoskeletal impact placed on the ligaments, joints, and tendons, especially during in-season competition.
Limitations of the current study are small sample size and the number of female participants. The results are based on recreationally active participants, and an athletic population would be desirable to see if this training stimulus has the same effect. In an ideal situation, it would be desirable to control or limit outside training regimens, so that the results can be solely based off of this training protocol and possibly not some outside training stimulus. Finally, incorporating another group that completes the same exercise protocol via a treadmill on land would be beneficial.
With this being said, these results can be beneficial for both strength and conditioning coaches and possibly athletes if this study is replicated with this population. If more studies that incorporate training with the use of ATM consistently demonstrate that participants are able to maintain or even increase performance variables while having less impact on their musculoskeletal system, then strength and conditioning coaches can incorporate water training into their regimens as another form of training. Training in the water can be most beneficial for athletes during their competitive season because the goal is to maintain their training status while placing the least amount of impact on their musculoskeletal system. Based on these current findings, an ATM Tabata interval training shows promise in maintaining and increasing performance variables. An 8-week ATM Tabata interval-training program presents a strong enough stimulus to cause increases in both flexibility and anaerobic power in terms of mean power while producing less impact on the musculoskeletal system. However, more research is needed such as recruiting participants from an athletic population, implementing different interval training protocols, and measuring other variables that may include but that are not limited to electromyography (EMG) activity of active muscle groups, pain, recovery, speed, and quadriceps-to-hamstring ratio strength.
Aquatic treadmill training has primarily been used as a form of training for those recovering from injury because of its low impact on the musculoskeletal system; however, if a strong enough stimulus is elicited, then this form of training can have a beneficial impact on one’s performance. Goals of strength and conditioning coaches are to improve athletes’ performance and to decrease the likelihood of injury by placing the least amount of impact on the body. These goals, as demonstrated by the current study with recreationally active participants, could possibly be achieved through ATM. Throughout a training cycle and competitive season, athletes’ bodies go through tremendous amounts of “wear and tear” that accumulates from all of the practices, games, and work-out sessions. An 8-week ATM Tabata interval-training program can be beneficial in preserving both athletes’ training status and their bodies as research has documented (2,6,10–13). This current study shows that with an intense enough form of exercise such as an 8-week Tabata interval-training program in the water, participants can maintain and even increase performance variables while decreasing the impact on their musculoskeletal system. Depending on the needs of the athlete and their sports, various interval-training protocols besides Tabata can be implemented by strength and conditioning coaches as long as a strong enough stimulus is elicited.
1. Baechle TR, Earle RW. Essentials of Strength and Conditioning (3rd ed.). Champaign, IL: Human Kinetics, 2008.
2. Cable T. Deep-water running. Insight 3: 45, 2000.
3. Dale RB. Deep water running for injured runners. Athlete Therapy Today 12: 8–10, 2007.
4. Di Prampero PE. The energy cost of human locomotion on land and in water. Int J Sports Med 7: 55–72, 1986.
5. Eyestone ED, Fellingham G, George J. Effect of water running and cycling on maximum oxygen consumption and 2-mile run performance. Am Sports Med 21: 41–44, 1993.
6. Glass B, Wilson D, Blessing D, Miller E. A physiological comparison of suspended deep water running to hard surface running. J Strength Cond Res 9: 17–21, 1995.
7. Kaminsky LA. ACSM’s Health-Related Physical Fitness Assessment Manual (3rd ed.). Philadelphia, PA: Lippincott Williams & Wilkins, 2010.
8. Loupias JP, Golding LA. Deep water running: A conditioning alternative. Health Fitness J 8: 5–8, 2004.
9. Michaud TJ, Brennan DK, Wilder RP, Sherman NW. Aqua running and gains in cardiorespiratory fitness. J Strength Cond Res 9: 78–84, 1995.
10. Miller MG, Cheatham CC, Porter AR, Ricard MD, Hennigar D, Berry DC. Chest- and waist-deep aquatic plyometric training and average force, power, and vertical-jump performance. Int J Aquat Res Educ 1: 145–155, 2007.
11. Quinn TJ, Sedory DR, Fisher BS. Physiological effects of deep water running following a land based training program. Res Q Exerc Sport 55: 386–389, 1994.
12. Reilly T, Cable NT, Dowzer CN. Does deep-water running aid recovery from stretch-shortening cycle exercise? Presented at Sixth Annual Conference of the European College of Sport Science; July 2001; Cologne, Germany.
13. Reilly T, Dowzer CN, Cable NT. The physiology of deep-water running. J Sports Sci 21: 959–972, 2003.
14. Silvers WM, Rutledge ER, Dolny DG. Peak cardiorespiratory responses during aquatic and land treadmill exercise. Med Sci Sports Exerc 39: 969–975, 2007.
15. Simpson A, Lemon P. Effects of an 8 week deep water vertical exercise training program in adult women. AKWA Newsletter 21–23, 1995.
16. Tabata I, Nishimura K, Kouzaki M, Hirai Y, Ogita F, Miyachi M, Yamamoto K. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2
max. Med Sci Sports Exerc 28: 1327–1330, 1996.