Sprint intervals: the verdict of the court

In recent years, a growing body of evidence has accumulated showing that performing regular bouts of high-intensity interval training is an extremely effective training tool for athletes seeking to maximize performance for a relatively low training workload⁽¹⁾. Put simply, short sessions of high-intensity intervals are a great way of producing gains in aerobic power, enabling an athlete to sustain a higher intensity/pace/workload for longer before fatigue sets in. And as we’ve discussed in previous SPB articles, high-intensity intervals are also a very time-efficient for the fitness gains achieved, easy to add to an endurance program, and psychologically less demanding to carry out – all of which explain why they have become so popular among athletes seeking to push their fitness to higher levels.

The rise and rise of sprint intervals

One of the key findings in the research on high-intensity interval training in recent years is that very short, very high intensity intervals of under 15 seconds’ duration can also be extremely effective for building fitness. For example, a Canadian study found that a HIIT program consisting of sessions consisting of six intervals of just 10 seconds sprinting produced significant gains in measures of aerobic fitness⁽²⁾! Other examples include research that found reducing interval lengths from 30 to 15 seconds produced the same magnitude of fitness as the original 30-second interval program⁽³⁾, and research on soccer players, which found that performing sessions of 15-second intervals was more effective than their normal soccer fitness program, with faster results!

Sprint intervals for sprint-sport athletes

As well as being a powerful and time-efficient tool for sharpening aerobic fitness, sprint interval training has also gained scientific attention for its ability to produce rapid improvements in anaerobic capacity and associated metabolic adaptations⁽⁴⁾. Because it challenges athletes to perform at or near maximal effort, sprint interval training promotes gains in power and speed, which are extremely important qualities for many athletes in a range of sports.

This gives sprint interval training a distinct advantage over steady-state endurance exercise, especially in sports such as soccer, tennis, basketball etc, which require intermittent but repeated bursts of speed and power. Indeed, research shows that by mimicking the physiological demands of these intermittent sports, sprint interval training can help athletes better prepare for the rigors of competition⁽⁵⁾. And as mentioned above, the time efficiency of sprint interval sessions make them appealing for amateur athletes with busy schedules such as work and family demands to accommodate⁽⁶⁾.

Sprint intervals for racquet sports

Racquet sports such as tennis and squash are characterized by a series of intense, short-duration efforts that demand rapid bursts of power, agility, and speed. These efforts include explosive serves, quick sprints to reach the ball, and forceful groundstrokes, all of which heavily rely on the anaerobic energy pathways⁽⁷⁾. The anaerobic/lactate system becomes dominant during extended rallies and intense baseline exchanges, where energy is required at a higher rate than can be delivered by the oxygen-dependent aerobic system⁽⁸⁾. This of course leads to the accumulation of lactate and muscular fatigue.

It follows therefore that a well-developed anaerobic energy system not only enables racquet players to execute powerful strokes and swift movements but also helps in delaying the onset of fatigue and sustaining peak performance during crucial match moments. That’s important because studies show that improving anaerobic capacity can lead to enhanced sprinting abilities, quicker court coverage, and better overall match performance⁽⁹⁾.

Given that a racquet sport player’s success hinges on the efficient utilization of the anaerobic energy system, and given that sprint interval training is highly effective at training that system (as well as giving gains in aerobic fitness), the obvious question is how effective can sprint interval training be for racquet sport players? It turns out that there’s actually very little research on this topic. Most of the existing studies on sprint interval training have primarily focused on cardiovascular benefits and metabolic changes among general or obese populations⁽¹⁰⁾. And those carried out on athletes have studied team sports such as soccer, basketball, volleyball, and field hockey^(11-13). Furthermore, most of these studies have been conducted in laboratory settings rather than in the settings where athletes actually practice their sport. Overall therefore it hasn’t been possible to answer this question.

Brand new research

The good news however is that brand new research on the use of sprint interval training for performance enhancement in tennis players has just been carried out. Published in the journal ‘Scientific Reports’, this study was carried by a team of Chinese researchers who investigated the impact of low-volume, court-based sprint interval training on the anaerobic capacity and sport-specific performance in competitive tennis players⁽¹⁴⁾.

Twenty-four male competitive collegiate tennis players participated in the study, which lasted for six weeks. These players were on average training for around 20 hours per week, which consisted of three hours of technical and tactical tennis practice per day and one hour of physical conditioning per day based on traditional endurance sessions performed five times per week. Following recruitment, the players were then randomized to one of two groups:

·        Sprint interval training – three sprint interval sessions per week with training taking place on Mondays, Wednesdays and Fridays.

·        Traditional endurance training - 45 minutes of continuous treadmill running at a velocity corresponding to 75% VO2max (moderately hard) three times per week on Mondays, Wednesdays and Fridays.

The sprint training protocol involved three sets of high-intensity sprints interspersed with short recovery periods, performed on the tennis court. Each interval run was 110 m in total distance and involved forward and backward sprints over distances ranging from 5-20 metres with multiple changes of direction (see figure 1). Each set comprised three repetitions of a 110-m sprint with a 20-second recovery period between each sprint, followed by a 5-minute recovery period between sets. For all training and testing sessions, regardless of group, the participants followed a 10-minute standardized general warm-up and 10-minute cool-down protocol including jogging, skipping, dynamic warm-up, and stretching.

Figure 1: The sprint training protocol