FOTEK - Sprint Interval Training (SIT) 5-km Run Performance Study (EN)

F OUR W EEKS OF S PRINT I NTERVAL T RAINING I MPROVES 5- KM R UN P ERFORMANCE J OSHUA D ENHAM , S IMON A. F EROS , AND B RENDAN J. RIEN Faculty of Health, Human Movement and Sport Sciences, Federation University Australia, Mt Helen, Victoria, Australia A BSTRACT emphasis on reducing training load to minimize injury risk but maximize training time to focus on other skills important to the sport. Sprint interval training (SIT) is an alternative mode of training to traditional constant-rate training as SIT improves cardiorespiratory fitness to a similar degree as constant-rate training but requires 90% less weekly energy expenditure and 66% less total training time (7).

Denham, J, Feros, SA, and O’Brien, BJ. Four weeks of sprint interval training improves 5-km run performance. J Strength Cond Res 29(8): 2137–2141, 2015—Sprint interval training (SIT) rapidly improves cardiorespiratory fitness but demands less training time and volume than traditional endurance train- ing. Although the health and fitness benefits caused by SIT have received considerable research focus, the effect of short-term SIT on 5-km run performance is unknown. Thirty healthy untrained participants (aged 18–25 years) were allo- cated to a control ( n = 10) or a SIT ( n = 20) group. Sprint interval training involved sprints at maximal intensity, 3 times a week for 4 weeks.

Sprints were progressed to 8 by the 12th session. All participants completed a 5-km time trial on a public running track and an incremental treadmill test in an exercise physiology laboratory to determine 5-km run perfor- mance and maximum oxygen uptake, respectively, before and after the 4-week intervention. Relative to the controls, sprint interval–trained participants improved 5-km run performance by 4.5% ( p , 0.001), and this was accompanied by improve- ments in absolute and relative maximum oxygen uptake (4.9%, p = 0.04 and 4.5%, p = 0.045, respectively). Therefore, short- term SIT significantly improves 5-km run performance in untrained young men.

We believe that SIT is a time-efficient means of improving cardiorespiratory fitness and 5-km endur- ance performance. Typically SIT consists of short, maximal efforts of 15–30 seconds, repeated several times interspersed with mi- nutes of recovery. Indeed, SIT may be more effective at improving endurance performance than both continuous running and other high-intensity interval training (HIT) pro- grams. For example, 20 individuals who completed 7–12 efforts of 30-second sprints thrice weekly for 6 weeks, improved 3-km run performance greater than individuals who completed constant-rate running or four to six 4- minute efforts at 3-km average running velocity, over 6 weeks (4).

Others have, however, demonstrated that recrea- tionally active participants similarly improve 2-km run per- formance after either 6 weeks of SIT (4.6%) or constant-rate running (5.9%) (13). Therefore, SIT seems to enhance run performance over km after 6 weeks of training, but whether these endurance benefits improve run performance in untrained participants in shorter time frames and over distances exceeding 3 km (a distance requiring greater reli- ance on aerobic metabolism) is unknown. Furthermore, the lack of inclusion of experimental controls in previous studies (4,6,13) obfuscates the genuine impact of SIT on endurance run performance.

Therefore, the purpose of this study was to determine whether a novel and relatively short-term (4 week), thrice weekly SIT program improves cardiorespiratory fitness and 5-km run performance. To that end, we assessed 5-km run performance and V _ O 2 max before and after either a novel 4-week SIT (four to eight 30-s maximal sprints, thrice weekly) program for cases ( n = 20) or no training for con- trols ( n = 10). We hypothesized that relative to the controls, the sprint interval–trained individuals would significantly improve 5-km run performance and V _ O 2 max.

I NTRODUCTION E ndurance run performance is important for indi- viduals of average cardiorespiratory fitness who aspire to improve their fitness and performance quickly and efficiently. Moreover, considering the importance of cardiorespiratory fitness and endurance per- formance in ball sports such as soccer, Australian Rules Foot- ball, and cricket (5,15,18), there is immense coaching Address correspondence to Joshua Denham, j.denham@federation.edu.au.

29(8)/2137–2141 M ETHODS Experimental Approach to the Problem This study is a controlled trial where healthy participants performed either 4 weeks of SIT or no training, to evaluate Journal of Strength and Conditioning Research 2015 National Strength and Conditioning Association VOLUME 29 | NUMBER 8 | AUGUST 2015 | 2137 Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. KEY WORDS time-trial, training load, SIT, V_ O2max

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SIT Improves 5-km Run Performance the effect of SIT on 5-km run performance and V _ O 2 max. V _ O 2 max was measured during a maximal treadmill test conducted in the University Exercise Physiology Labora- tory and the 5-km time trial was assessed at a public run- ning track. These tests were performed on separate days within 1 week of commencing the initial SIT session and within 1 week after the final SIT session. (ml kg min 2 1 ) 49.57 6 6.71 49.29 6 6.67 2 0.28 0.72 1.69 0.967 (0.867–0.992) 3.6 (2.5–6.7) time-trial (s) 1,478.10 6 349.95 1,447.50 6 347.24 2 30.6 0.18 47.07 0.991 (0.963–0.998) 3.4 (2.4–6.4) * ICC = intraclass correlation; CV = coefficient of variation.

Results of the 5-km time-trial test in the control group ( n = 10), reliability as measured by mean difference of 2 trials, ICC, p value (2-tailed paired t -test), SEM , and typical error as a CV percentage. Upper and lower confidence intervals are expressed in parentheses; confidence intervals are set at 95%. SD s are represented after the mean of trials 1 and 2. Variable Mean trial 1 Mean trial 2 Mean difference p SEM ICC CV (%) Subjects Thirty, apparently healthy young men (18–25 years) were recruited for this study. Participants were initially screened to ensure they were not currently engaging in any struc- tured high-intensity aerobic exercise training.

All partici- pants had not completed any structured aerobic exercise training in the past year. Twenty participants were allocated to the SIT (cases) group, and 10 participants were allocated to the control group. Participants gave written informed consent, and this study was approved by the University’s Human Research Ethics Committee. Procedures Participant V _ O 2 max was assessed during a maximal tread- mill test, by pulmonary analysis conducted in an exercise physiology laboratory at the University.

Before the V _ O 2 max test, participants were fitted with a 2-way breathing valve (Hans Rudolph, Lenexa, KS, USA), and expired air was collected into an online metabolic system (Moxus Modular, Pittsburgh, PA, USA) for gas (O 2 and CO 2 ) analysis. The metabolic system was calibrated before each test using ambient air and gas of known composition. Participants T ABLE 1. Description of the 4-week sprint interval training program. T ABLE 2.

Test-retest reliability data for the 5-km time-trial test.* Training Training Total session Week Session number load (sprints) sprint time (min) time (min) 1 1 3 1.5 9.5 2 4 2 14 3 5 2.5 18.5 2 4 4 2 14 5 5 2.5 18.5 6 6 3 23 3 7 5 2.5 18.5 8 6 3 23 9 7 3.5 27.5 4 10 6 3 23 11 7 3.5 27.5 12 8 4 32 Total 66 33 249 V _ O 2 max time 5-km the TM 2138 Journal of Strength and Conditioning Research Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

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Journal of Strength and Conditioning Research the TM | www.nsca.com were given a standardized 3-min warm-up at 10 km hour 2 1 . The V _ O 2 max test was commenced at 10 km hour 2 1 , and treadmill speed was progressively increased by 1 km hour 2 1 completed a standardized warm-up entailing a 5-min aerobic warm-up, dynamic stretches, and some short (20 m) runs at approximately 70, 80, 90, and 100% effort. every second minute until volitional exhaustion. V _ O 2 max was determined as the highest O 2 value averaged over 60-s. All laboratory testing was performed preprandially at the same time of day (8–10 AM ). Participants were encouraged to hydrate the night before and morning of testing.

Within a week of the V _ O 2 max assessment, each participant completed a supervised 5-km run time trial on a flat running track in a local park. Participants were familiar with 5-km circuit and were advised to hydrate before running. All testing was con- ducted in the afternoon (4–6 PM). Briefly, participants com- pleted a short 10-min warm-up including some light aerobic exercise and dynamic stretches. Participants were supervised and instructed to run maximally at their own pace. All participants were instructed not to deviate from their current physical activity, exercise (if any), and dietary habits during the 4-week intervention period.

Statistical Analyses All statistical analyses were performed using IBM SPSS Statistics for Windows (Version 20, IBM Corp., Armonk, NY, USA). Data were tested for normality using the Kolmogorov-Smirnov and Shapiro-Wilk tests, and nonpara- metric data were log-transformed before further analysis. Paired samples t -tests were used to examine fitness and per- formance changes after SIT, relative to the control group. To ascertain the test-retest reliability of V _ O 2 max and 5-km time- trial performance, the intraclass correlation coefficient (2, k), coefficient of variation (log-transformed), SEM , and system- atic bias (determined by paired samples t -test) were calcu- lated.

Significance was set at p # 0.05. Cases completed a standardized SIT program performed 3 times a week over 4 weeks (total of 12 sessions). The sprint duration and recovery period was controlled at 30-s and 4- mins (passive), respectively. Participants were requested to run maximally without pacing for each 30-s sprint. All training was conducted on the University’s sports oval, and an Ac- credited Exercise Physiologist (with Exercise and Sport Sci- ence Australia) provided participants with verbal encouragement and supervised each training session. The SIT volume increased from 4–8 sprints over the 4-week inter- vention (Table 1).

Before each training session, participants R ESULTS Test-retest reliability data is outlined in Table 2. The 5-km time-trial test had excellent reliability with an intraclass cor- relation coefficient of 0.99 and a 3.4% coefficient of variation. Figure 1 outlines the fitness and performance changes after 4 weeks of SIT. Relative to the control group who showed a marginal increase in 5-km time-trial performance (mean 6 SD : 1,478 6 350 to 1,447 6 347, 2 2%, p = 0.20, Table 2 and Figure 1), cases had a significant improvement in 5-km time-trial performance by an average of 65 seconds (mean 6 SD : 1,464 6 298 to 1,368 6 270, 2 4.4%, p , 0.001) after 4 weeks of SIT (Figure 1).

Although absolute and relative V _ O 2 max increased after SIT in cases (mean 6 SD : 3.8 6 0.6 to 4.0 6 0.6, 4.9%, p = 0.04 and 49.6 6 4.6 to 51.4 6 3.8, 4.5%, p = 0.045, respec- tively), absolute and relative V _ O 2 max were unchanged in controls (mean 6 SD : 3.7 6 0.6 to 3.7 6 0.6, 0.6%, p = 0.73 and 49.6 6 6.7 to 49.3 6 6.7, –0.6%, p = 0.72, respec- tively, Table 2 and Figure 1). Figure 1. The 5-km time-trial performance and relative V _ O 2 max before and after sprint interval training (SIT). Relative to the controls ( 2 2.1, p = 0.20), the cases had a significant improvement to 5-km run performance ( 2 4.4%, p , 0.001) and relative V _ O 2 max (4.5%, p # 0.05) after SIT.

Data are expressed as mean values before and after either 4 weeks of SIT (cases) or no exercise training (controls). * p # 0.05; *** p , 0.001. D ISCUSSION The purpose of our study was to determine whether a novel VOLUME 29 | NUMBER 8 | AUGUST 2015 | 2139 Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

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SIT Improves 5-km Run Performance and short-term (4 week), thrice weekly SIT program improves cardiorespiratory fitness and 5-km run perfor- mance in untrained men. To our knowledge, we are the first to demonstrate that 5-km run performance is signifi- cantly improved after short-term (4 weeks) low-volume SIT. Considering the marginal but not statistically significant improvement in the controls (31 seconds, 2%), the marked (96 seconds, 6.5%) improvement after 4 weeks of SIT translated to a mean 65 seconds (4.4%) faster 5-km run performance in cases. Notably, 5-km run performance was improved in conjunction with increased V _ O 2 max (4.5%).

cardiac output may have facilitated the improvement in 5-km run speed, as opposed to improvements in muscle oxidative capability, based on the concepts that V _ O 2 max is chiefly governed by the maximal cardiac output and the lactate threshold by muscle oxidative capability (12). Other mechanisms by which SIT may enhance 5-km run perfor- mance include improved run economy, running mechanics, and potassium regulation. It was previously reported that moderately trained runners’ run economy was improved by 7% after 4 weeks of SIT, but these subject did not improve their 10-km time-trial performance (11).

Moreover, increases in knee flexor endurance, coupled with decreases in knee flexion torque and knee flexion/extension ratios are also adaptations associated with sprint training that could have contributed to the improvement in 5-km run performance observed in our study (19). Others have shown in well- trained runners, SIT enhanced key components of the Na + /K + pump that would aid to minimize disturbances in nerve membrane potential and maintain sprint performance, and this was associated with an approximate 3% improve- ment in 3-km and 10-km run performance (1).

The increase in muscle oxidative and anaerobic enzyme activity are adap- tations gained from SIT and is another possible mechanism for the facilitated endurance performance observed in par- ticipants from our study (2,3,8,16). Our data showing SIT enhances 5-km run performance corroborates others showing SIT enhances 2-km (13) and 3-km (4,6) run performance in recreationally trained individ- uals. We are the first to demonstrate 4 weeks of 3 times per week SIT, in the form of running, significantly improves 5-km run performance—a prestigious and Olympic running distance. Interestingly, the impact of SITon 5-km endurance performance is established in other exercise modalities.

A short-term (2-week) cycle SIT intervention improved 5-km cycle performance to a similar magnitude to our protocol (5.2%) (10). Whether SIT improves run performance over longer distances warrants attention. Additionally, whether SIT benefits already well-trained runners is yet to be fully understood, as data have, to date, been equivocal (1,11). Nevertheless, we verify SIT as an effective means of improv- ing running endurance performance in untrained young men. A limitation of our study is that we did not include females. Some of the benefits gained from SIT seem to be dependent of gender.

For example, males had greater muscle protein synthesis of proteins important for mitochondrial biogenesis after 9 sessions of SIT compared to their female counterparts (17). Given these muscle adaptations are vital for endurance performance (2,8,9), whether short-term SIT improves 5-km run performance in females is left for future investigations. The increased 5-km run performance in our study is similar to previously observed improvements after traditional constant-rate endurance training. It was reported that an intervention of 3 running sessions per week at 75% of V _ O 2 max for 6 weeks improved 5-km run time by approxi- mately 80 seconds ( ; 5%) in 39 untrained individuals (20).

Additionally, others have shown that 5-km time trial improved by 78 seconds (5%) in a group that ran for 20 mi- nutes 3 times per week for 6 weeks, initially starting at 0.8 km hour 2 1 below their individual lactate threshold speed with progression to 0.8 km hour 2 1 above their individual pretraining lactate threshold speed (14). Importantly, a con- trol group was not included in these studies to establish the error of the 5-km time-trial test, which we established was 31 seconds. Collectively, it seems that SIT improves 5-km run performance to a similar extent as constant-rate training but in a quicker time frame (4 vs. 6 weeks) and a smaller training duration (249 minutes vs.

360 minutes) (14). Future research could focus on optimizing training variables, such as the recovery time between sprints, number of sprint repetitions, time required of each sprint, number of sessions required per week, and the optimal length of SIT to improve fitness and performance. In fact, the efficiency of HIT in evoking positive adaptations may even be more potent than originally envisaged. It was recently revealed that 1 maximal 4-min effort at 90% of heart rate maximum on a cycle ergometer performed 3 times a week for 10 weeks improves V _ O 2 max by an average of 10% (21).

In conclusion, our data reveal that SIT is a highly effective strategy to improve endurance running quickly in previously untrained young men. The improvement in run performance was accompanied by a corresponding improvement in V _ O 2 max. Although pre- vious constant-rate training studies have demonstrated par- ticipants increased their V _ O 2 max to a similar magnitude observed in the our study (3.8–7.7%), they also showed marked improvements in their participants lactate threshold, which could have contributed to the improvements in run performance (14,20), particularly because not all cases had improvements to V _ O 2 max.

Alternatively, an improvement in P RACTICAL A PPLICATIONS Physical conditioning professionals must be aware of effi- cient means of exercise training that augment cardiorespira- tory fitness and endurance performance. The results from our study support the use of short-term low-volume SIT as an effective means for rapidly improving cardiorespiratory fitness and endurance performance. Therefore, team sport the TM 2140 Journal of Strength and Conditioning Research Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

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