Whilst the use of small sided games (SSGs) as a conditioning tool within team sport has been successfully implemented in combination with technical outcomes (1), its longitudinal efficacy at eliciting a standardised acute physiological response within a team of heterogeneous physiological profiles has been questioned due to an inherent ceiling effect occurring amongst fitter players (2). It has been argued that in regard to central adaptations a sustained cardiac filling is integral to achieving adaptations such as left ventricular eccentric hypertrophy (3). Variations of movement tasks and irregular work:rest ratios during SSGs may alter venous return and pump action, which consequently may compromise acute stroke volume and long term myocardium enlargement. For this reason, metabolic conditioning should not only account for the demands of the sport, but perhaps more importantly apply the specificity principle to the athlete’s physiology. Thus, the remainder of this article shall focus on methods of prescription using individualised velocities obtained from field tests (4).
Though the ASR is essential for accuracy of individualised prescription, it does not allow for consideration of onset of oxygen kinetics, inter-effort recovery and change of direction abilities (2). These qualities are ubiquitous both within HIT sessions utilised within team sport as well as within competition itself. It follows that calculating MAS from incremental tests (e.g. bleep test; Montreal track test) or time trials possess inherent flaws that render the estimation with low construct validity. Practitioners have therefore sought superior alternatives (4).
The Yo-Yo Intermittent Recovery (Yo-Yo IR1) Test is a high-intensity intermittent shuttle test that captures the aforementioned qualities in totality (5). It has also been shown to have high reliability and validity in elite male soccer players (6). However, its use as an assessment tool is often assumed to have equal validity for prescription. The relationship between velocity achieved at the end of the Yo-Yo IR1 test (VYo-YoIR1) and vV̇O2max is contingent on velocity (7). Specifically, when VYo-YoIR1 is either below or above 16.3 km/h, it has a tendency to overestimate and underestimate vV̇O2max respectively. Thus, once can expect large interindividual variation resulting in some athletes ‘cruising’ while others struggling to complete the set, despite the same relative intensity being prescribed.
The 30-15 Intermittent Fitness Test (30-15IFT) is an intermittent shuttle test that has demonstrated reliability and validity for both assessment and prescription of supramaximal intermittent locomotor ability (8). The set-up is portrayed in Figure 1. The velocity achieved at the end of the test (VIFT) stresses key physiological responses including recruitment of high threshold motor units, inter-effort recovery abilities and change of direction qualities (8). Furthermore, end-stage velocities elicit peak oxygen uptake and the 40m shuttle distance permits attainment of supramaximal running speeds that are closer to MSS than VYo-YoIR1 (9). Thus, VIFT has greater sensitivity to the athlete’s physiological profile and is able to better standardise acute physiological responses. Consideration of acute session responses are depicted in Figure 2.
Figure 1. Area prepared for the 30-15IFT. Participants start at line A, run through line B to get to line C (40-m) and then return. This is repeated for 30 s. During the 15 s recovery period, participants walk in the forward direction to the nearest line. Distance covered within the 40-m shuttle will vary according to the running speed, hence why participants may start and finish at different lines (A, B or C) depending on the running stage speed. Participants must be within the 3 m zone of each line on the pre-recorded beep.
Figure 2. Acute high-intensity interval session physiological responses alongside variables of interest for session prescription. Variables highlighted in red delineate intensity of work completed and profoundly impact T @ VO2max. Variables highlighted in white delineate total work completed and profoundly impact anaerobic glycolytic contribution. Variable delineated in green profoundly impacts nature of musculoskeletal strain. Notes: T @ VO2max = Time spent at 90% VO2max i.e. red zone; Anaerobic Glycolytic Contribution = Glycogen depleting nature of session, accounting for blood lactate responses; Neuromuscular Load = Neural adjustments in motor unit recruitment and force generating capacity; Musculoskeletal Strain = Impact on locomotor muscles, joints, tendons and ligaments.
Finally, whilst it is beyond the scope of this article to discuss energy system periodisation strategies, it would be remiss not allude to planning individual units within the micro-cycle. The reader is encouraged to consolidate nine key session variables that are presented in Figure 2. The goal of the HIT session is to maximise time spent in the red zone (90% V̇O2max), with 5-7 minutes for team sport athlete likely to be sufficient to elicit optimum cardiopulmonary adaptations (~10 minutes for endurance athletes) (2). With this in mind, contemplation of session efficiency is paramount, which can be quantified by dividing time in the red zone by total exercise time. One can easily quantify total session time, but what about time in the zone? Unless one has the luxury of a portable gas analyser, this would represent logistical difficulty. Added to this, using short intervals (< 60s), V̇O2max would likely be approached towards the latter stages of the first set, providing sufficient intensity. This represents a loss of valuable training time and potential for adaptation.
The practical solution to this is prescribing a ramped warm-up for a graded return that in turn accelerates V̇O2 kinetics, specifically the V̇O2 slow component (10). The goal is to achieve V̇O2 priming so that athletes approach the red zone prior to their first repetition. The balancing act boils down to this: a ramped warm-up has to be sufficiently intense to prime oxygen kinetics vs. sufficient recovery time between cessation of the warm-up and the start of the HIT session that facilitates removal of accumulated metabolites, whilst continuing to accelerate development of the V̇O2 slow component (9). In doing so, oxygen debt is reduced resulting in decreased anaerobic glycolytic contribution and increased time to exhaustion (9), which in turn may lead to more prominent adaptations. An example protocol is illustrated in Figure 4.
Figure 4. On-field protocol outlining preparation for high-intensity interval training session in view of priming oxygen kinetics and accelerating the VO2 slow component.
It is more than just running hard. Training needs to be prescribed in accordance with the athlete’s physiology to maximise long term adaptation and minimise interference across the microcycle. Maximising time in the red zone can be achieved via the priming effect of a prior intervention. Finally, well-considered manipulation of session variables is required in order to take ownership of the desired physiological adaptations.
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(2) Buchheit, M., & Laursen, P. B. (2013). High-Intensity interval training, solutions to the programming puzzle. Part I: Cardiopulmonary emphasis. Sports Medicine, 43, 313-338
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(4) Clarke, R., Dobson, A., & Hughes, J. (2016). Metabolic conditioning: Field tests to determine a training velocity. Strength and Conditioning Journal, 38, 38-47.
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(7) Dupont, G., Defontaine, M., Bosquet, L., Blondel, N., Moalla, W., & Berthoin, S. (2010). Yo-Yo intermittent recovery test versus the Université de Montréal Track Test: Relation with high-intensity intermittent exercise. Journal of Science and Medicine in Sport, 13, 146-150.
(8) Buchheit, M. (2008). The 30-15 intermittent fitness test: Accuracy for individualizing interval training of young intermittent sport players. Journal of Strength and Conditioning Research, 22, 365–374.
(9) Buchheit, M., Al Haddad, H., Millet, G. P., Lepretre, P. M., Newton, M., & Ahmaidi, S. (2009). Cardiorespiratory and cardiac autonomic responses to 30-15 intermittent fitness test in team sport players. Journal of Strength and Conditioning Research, 23, 93–100.
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