This is an excerpt from Science and Application of High-Intensity Interval Training.
Recall that weapons refer to the high-intensity interval training (HIIT) formats we can use to target the physiological responses of importance, while the surveillance tools are what we are using to monitor the individual responses to those weapons (figure 1.5). In this section, we present the different HIIT weapons, their manipulations, along with ways to monitor their effectiveness (surveillance).
In our experience, we typically target throughout the season all HIIT target types (see figure 1.5), with the exception of type 5 (type 1: metabolic O2 system; type 2: metabolic O2 system + neuromuscular; type 3: metabolic O2 + anaerobic systems; type 4: metabolic O2 + anaerobic systems and neuromuscular). As shown in figure 30.2, the very large majority of the weapons used to reach these targets are game-based HIIT, with the majority of them being in the format of small-sided games (SSGs) (70%, both pre- and in-season), followed next by short intervals (20%, both pre- and in-season, essentially for individual top-ups and rehabilitation), repeated-sprint training (RST) (5%, both pre- and in-season, essentially for individual top-ups), and long intervals (5%, preseason exclusively).
Manipulations of Interval Training Variables
The running intensity and modality of each HIIT format is systematically modulated to reach the desired acute metabolic and locomotor responses (i.e., physiological targets, types 1, 2, 3, or 4), which, in turn, solves the programming puzzle on a weekly basis for us.
Factors to consider when choosing an HIIT session type for soccer include match-play demands, player profile, desired long-term adaptations, and training periodization. Together, these factors determine the desired physiological response target type, including type 1 aerobic metabolic, with large demands placed on the oxygen (O2) transport and utilization systems (cardiopulmonary system and oxidative muscle fibers); type 2 metabolic as per type 1 but with a greater degree of neuromuscular strain; type 3 metabolic as per type 1 with a large anaerobic glycolytic energy contribution but limited neuromuscular strain; type 4 metabolic as with type 3 but with a high neuromuscular strain. The type 5 target, a session with limited aerobic demands but with a large anaerobic glycolytic energy contribution and high neuromuscular strain, is rarely if ever used in our context. The type 6 response (not considered HIIT) refers to typical speed and strength training with a high neuromuscular strain only. Note that for all HIIT types that involve a high neuromuscular strain, possible variations of the strain include more high-speed running (HS, likely associated with a greater strain on hamstring muscles) oriented work or mechanical work (MW, accelerations, decelerations, and changes of direction, likely associated with a greater strain of quadriceps and gluteus muscles).
HIIT With Long Intervals (Outdoor)
Because of their important (but less soccer locomotor-specific) neuromuscular load and anaerobic contribution (type 4), we generally implement HIIT with long intervals exclusively during the preseason over a 300 m loop designed around the pitch. These typical HIIT exercise bouts are generally performed over 3 to 4 min at 90%-95% VIncTest or 80% VIFT (see chapter 2). This represents 800 to 1000 m efforts completed over 3 min, depending on player fitness, with athletes running 3 to 5 repetitions interspersed by 2 min of passive recovery. Players are generally spread across 4 groups (16 km/h, 17 km/h, 18 km/h, and >18 km/h for VincTest or 18 km/h, 19 km/h, 20 km/h, and >21 km/h for VIFT) and are requested to reach group-specific cones set across the running loop at appropriate times. These sessions are generally prescribed at the end of the day, so that athletes may benefit from a greater (O2 slow component, i.e., higher (O2 for a similar or lower running speed due to muscle fatigue and loss in metabolic efficiency), which may help in limiting overall musculoskeletal strain and fatigue. Importantly, this HIIT format also has an advantage in that it stresses the cardiopulmonary system at high rates without the need for reaching high running speeds (<18-19 km/h). This is of primary importance for the weekly high-speed running load management, since it leaves room for the other sessions to target this locomotor component with less risk of locomotor or musculoskeletal overload.
HIIT With Short Intervals
Our preferred HIIT short-interval weapons include 10 s on/10 s off, 15 s/15 s, 20 s/20 s, and more often 10 s/20 s (figures 30.3 and 30.4) since this latter format has been shown to be low with respect to acute neuromuscular fatigue (figure 5.41). We implement these HIIT formats for the main reason that both the volume and intensity of the locomotor load (i.e., high-speed running and mechanical work), and in turn, the associated neuromuscular load and fatigue and anaerobic contribution, can be tightly manipulated. For example, type 1, 2, 3, or 4 targets can all be hit with short intervals. While we may sometimes use these HIIT formats in the preseason during a few collective team training sessions, HIIT with short intervals is of greater use to us in-season for individual players requiring well-tailored locomotor loads, i.e., rehabilitating players or conditioning substitute players, for which collective game-based training may not be recommended or fulfill their needs completely. In fact, programming HIIT with low levels of neuromuscular load (type 1) may be required during the preseason to assist with preserving the quality of the conjoined soccer sequences (same session) as well as the type 6 strength and speed sessions planned the following day (see chapter 6). Similarly, during rehab, it may be prudent to start with type 1 HIIT before progressing, depending on the type of injury, toward hitting type 2 targets (tailored toward either more high-speed running versus mechanical work, figure 30.3), followed by type 3 targets, and finally, type 4 targets. For substitute players, HIIT with short intervals is generally the only weapon available as a top-up to compensate for the high-speed running load that players miss while not playing, since the large majority of SSGs in which they participate (figure 30.5) fail to overload this locomotor component respective to match demands.
In practice, we generally spread the players into 5 groups (17 km/h, 18 km/h, 19 km/h, 20 km/h, and >21 km/h for VIFT) and request they run over group-based distances using cones on the pitch. For example, for players with a VIFT of 19 km/h, and for a 15 s/15 s HIIT run at 95% VIFT (relief interval: passive), the target distance will be (19/3.6) × 0.95 × 15 = 75 m (19 is divided by 3.6 to convert the speed from km/h to m/s, for convenience). When we plan runs with changes of directions (CODs) to decrease the amount of high-speed running and modulate mechanical work, the time needed for COD must also be considered when setting the target run distance in order to ensure a similar cardiorespiratory load compared to straight-line runs. Therefore, in relation to the estimated energetic cost of COD during HIIT (see chapter 2, VIFT section), if the players have to run over a 40 m shuttle, for example, they would instead cover 71 m. If the shuttle length is divided in half (i.e., 20 m shuttle), the distance they must cover drops to 65 m. (A spreadsheet that completes this calculation for 180° CODs for 15 players at a time is available through the 30-15 IFT App: https://30-15ift.com/.) Finally, to further modulate the locomotor demands and, in turn, the neuromuscular load of these runs, we use turns at different angles that can either decrease or increase braking and acceleration demands. In fact, using research technology that included measures of ground impacts and muscle activity and oxygenation during (repeated) high-intensity runs (https://www.youtube.com/watch?v=KFL8STOyaB0), we showed that while straight-line runs promote stride work (and hamstring loading) via increased high-speed running (HS, type 2 or 4), sharp turns (90°-180°) rather increase thigh work (quads and glutes) via the increased neuromuscular requirements associated with deceleration and acceleration phases (i.e., increased mechanical work, type 2 or 4). Interestingly, we also showed that 45° turns were likely associated with the lowest neuromuscular load, since neither high-speed nor sharp decelerations and accelerations are involved within this condition (type 1).
To make HIIT with short intervals more appealing to players and a bit more specific in terms of movement patterns and locomotor loading, the ball is often integrated into the activity on different occasions. For example, players run following position-specific running patterns for the required duration while reproducing position-specific technical sequences including passes, receptions, and/or shots on mini-goals at the end of the run (figure 30.3).
Finally, while the optimal loading in terms of HIIT volume and, in turn, high-speed running distance and mechanical work is difficult to define, we often use match demands as targets. For example, we progressively build up locomotor loads during rehab to reach the match-play distance equivalent of 45, 60, and 90 min or sometimes more. We also use within-player load modeling such as the acute/chronic ratio (and associated predictions) for both rehab and healthy players to define volume targets at different times of the week. For example, considering that a competitive match requires players to cover 600 to 1300 m >19.8 km/h (2), compensation training the day following the match including a 6 min HIIT (in which series duration and volume are based on player's profile and position) may allow substitutes to maintain their weekly high-speed running volume at a stable level, which may limit injury risk before the next match.