Physical Game Demands of Ice Hockey Part 1: Work Capacity
The Demands of Ice Hockey
This series of articles aims to review current literature that defines ice hockey game play in order to offer recommendations as to the key physical areas needed for athletic development. Ice hockey game performance is defined by high intensity intermittent bouts of skating characterized by maximal accelerations, changes in direction and high impact body collisions (1–4).
Understanding the inherent physiological and biomechanical characteristics of game play across the many levels of competition is needed to develop a holistic view of the game requirements and fatigue patterns. In particular, identifying off and on-ice physical relationship trends and assessing activity profiles of competition for forward and defensemen positional groups is critical if effective sport specific training programs are to be designed.
In part 1 of this series we will review the cardiovascular characteristics of game play with specific analysis into the metabolic profile of both positional groups. This article will also identify current research into the locomotive demands of game play via player tracking technology. Part 2 will assess the strength, power, speed, and body composition needs that support performance for game specific events.
Assessing the Work Capacity Needs of Hockey Players
Ice hockey games consist of three 20-minute stop time periods separated by two breaks lasting 18 minutes with the total 60-minute game duration extended over approximately 3 hours. Shifts last between 30-80 seconds and rarely exceed 90 seconds, with approximately 50% of a shift classified as effective playing time and the remainder as stoppage (5). Cumulative active game time has been demonstrated to be on average 16.1 ± 3.6 minutes during three periods of international game play (5). However, active game time can be in excess of 30 minutes and is dependent on playing position and game scenarios such as the need for an overtime period.
Analysis of National Hockey League (NHL) shift data has revealed that forwards perform an average of 6.8 ± 1.1 shifts per period, each lasting 45.5 ± 3.9 seconds with a rest interval of 73.4 ± 16.6 seconds (6). It has been estimated that 50% of active shift time is spent at high intensity activity, which infers approximately 22.7 seconds of a shift may be performed in a maximal or near maximal skating state (6).
The high intensity nature of each period has been demonstrated in the significant depletion of muscle glycogen stores in the vastus lateralis (your side quad muscle) after a game (7). Consequently, each shift requires high anaerobic power and endurance to support maximal and repeated sprint skating efforts (4,8).
Physiological measures of heart rate responses have been used to demonstrate in-game exercise intensity in response to gameplay. A study by Stanula et al. (4) tracked the heart rates of 16 players competing for a national under-20 ice hockey team over 4 games. This study reported maximum heart rates of 194.7 ± 8.3 – 190.7 ± 6.2 bpm and average heart rates of 159.1 bpm - 150.7 bpm across 1:17:47 and 1:17:54 of game time for forwards and defensemen, respectively.
These values were collected across the entire game and included stoppages and time spent sitting on the bench. Average shift heart rates in female collegiate ice hockey players have also been reported to be 92% of a player's maximum heart rate (HRmax) demonstrating the high intensity nature of a shift (9).
Energy for the maximum intensity aspects of a shift is supplied by anaerobic metabolism resulting in depletion of adenosine triphosphate phosphocreatine (ATP-PC) stores and a corresponding increase in inorganic phosphate, accumulation of hydrogen ions, increase in lactate formation, and decrease in muscle PH (10,11). These mechanisms all support an increase in fatigue and a decline in power output.
Consequently, prolonged periods of moderate to low intensity locomotive activity (such as standing and gliding) and recovery (during stoppages, time on bench or between period breaks) may reflect the importance of the aerobic system in the restoration of metabolites to normal levels.
Do Hockey Players Need to Train Aerobic Capacity?
Conflicting evidence however exists identifying the association between off-ice and on-ice measures of aerobic capacity. Durocher et al. (12) showed off-ice VO2max and lactate threshold assessment (cycle ergometry) significantly underpredicted the same measures produced from a graded on-ice skating test. Carey et al. (11) found no significant correlations between treadmill assessed measures of VO2 max and recovery capacity during an on-ice repeated sprint ability (RSA) test. However, Stanula et al. (10) reported off-ice aerobic capacity to be significantly correlated to on-ice fatigue index (r = -0.584, p = 0.003) during RSA in senior national male ice hockey players.
These discrepancies may reflect the limitations associated with using off-ice aerobic measures that demonstrate a lack of correspondence to on-ice demands as well as the issues inherent with the varying methodological parameters used to assess RSA (13,14). A recent study by Peterson et al. (6) addressed some of these issues by accounting for task specificity in testing VO2 peak on a skating treadmill.
This study also evaluated RSA using an on-ice repeated shift test developed to recreate the motor patterns performed during competition. Consequently, maximal oxygen uptake was found to significantly correlate (r = -0.31, p = 0.04) to markers of fatigue expressed as a decrement score at the end stage of each RSA bout in collegiate level ice hockey players.
The importance of aerobic fitness has also been related to markers of game performance. A recent study analyzing the aerobic capacities of NHL players via a sub-maximal on-ice Yo-Yo intermittent recovery ice hockey test found cardiovascular load correlated significantly with in game measures of high intensity skating distance and the frequency of high intensity skating bouts (3). Green et al. (15) demonstrated significant correlations between VO2 max and net scoring chances (r = 0.41, p < 0.03) over a full national collegiate ice hockey season.
This study suggested greater aerobic abilities increase a player's involvement in both the offensive and defensive end resulting in increased scoring opportunities and more effective defensive play. Consequently, aerobic capacity appears to be responsible for supporting recovery from high-intensity repeated work bouts and increasing time to fatigue in ice hockey. This may be achieved through mechanisms associated with hydrogen ion buffering and an increase in muscle PH which reduces fatigue and minimizes the attenuation of power output during subsequent shifts (13).
Athletes with higher aerobic capacities may also be more resistant to fatigue due to an increased ability to enhance oxidative phosphorylation during intense shifts when glycolytic pathways are inhibited (16). Both anaerobic and aerobic fitness development is critical for successful performance as the energy pathway and muscle oxidative demands for ice hockey requires proficiency across the entire continuum of energy systems.
Work Capacity Differences for Hockey Forwards and Defensemen
Differences in metabolic profiles also exist for defensemen and forwards during high-level game performance. Defensemen have been reported to spend 21% more active game time in moderate intensity heart rate zones (between 76.4 and 89.0% of HRmax) and 20% more in higher intensity heart rate zones (exceeding 89.5% of HRmax) vs. forwards (4). In support of these metabolic differences, activity profiling during an NHL game via multiple camera tracking analysis demonstrates defenseman cover significantly more skating distance (+29%) than forwards (5445 ± 337 m vs. 4237 ± 248 m), yet forwards perform significantly more high intensity sprint skating (+54%) than defensemen (139 ± 4 vs. 90 ± 6 m.min-1) (3).
A recent increase in the availability of wearable player monitoring technology in ice hockey has also provided an opportunity to understand the locomotive demands of gameplay. Subsequently, the different movement requirements between positional groups have been identified through external load measurements. Allard et al. (17) analyzed professional players across a 76-game season via the use of inertial measurement units with accelerometry and reported defensemen achieve significantly lower total game skating intensities than forwards (-1.7 on-ice load ⋅min-1 on average). Similar accelerometry based measurements during national female competition have reported greater measures of skating intensity via player load⋅min-1 (p < 0.001, ES = 0.55) and explosive skating efforts (p < 0.001, ES = 0.63) during games for forwards versus defensemen (18).
Recently, local positioning systems have been introduced in ice hockey to track velocity and distance during competition. Douglas et al. (19) utilized this method to track elite male ice hockey players during 5 international games and found defensemen skated significantly higher distances at very slow (1.0-10.9 km/h), slow (11.0-13.9 km/h) and moderate (14.0-16.9 km/h) speeds whilst forwards covered greater distances at fast (17.0-20.9 km/h), very fast (21.0-24.0 km/h) and sprint (>24 km/h) speeds during games.
It appears that forward and defensemen accumulate game load and skating distance in markedly different ways. Consequently, forwards are defined by a greater frequency and number of maximal sprints, higher average shift speed with a reduced total number of shifts versus defensemen (3,7,17,18). Discrepancies between positions during games could reflect game tactics, as elite competition requires forwards to skate hard at opponents in all three zones to support an aggressive forecheck (18).
These differences may also be the result of the team carrying 4 forward lines versus 3 defensive pairings, meaning defensemen spend a greater amount of time on the ice with a higher number of total shifts (20.7 ± 2.3 vs. 15.3 ± 2.2 for forwards), which may explain the greater total skating distance and time in moderate/high intensity heart rate zones achieved by this group (3,17,20). It is also worth noting that differences in the physical performance of skating velocity and distance during a game are influenced by abnormal play scenarios termed “special teams”. Specifically, defensemen have been shown to produce higher skating speeds and distances when on a power play (5v4 player advantage) compared to the penalty kill (4v5 player disadvantage), whilst forwards demonstrate the opposite (19). Consequently, the movement demands of a positional group during a game are impacted by the number of penalties called.
Analyses into the physical characteristics that differentiate elite player draft entry selection have reported higher anaerobic fatigue resistance capacities in defensemen when compared to forwards (8). This may be due to the greater demand for sustained power outputs due to longer and more frequent shifts for defensive positions (3,8). It has also been reported that aerobic power (absolute V02 max) is not a differentiating factor for elite player status for either forwards or defensemen (8). This suggests that aerobic metabolism is a universally important energy system that both positions require if game performance is to be optimized (8).
Final Thoughts on Work Capacity for Hockey Players
It is clear both skating positional groups require the development of high intensity intermitted training programs. However, on-ice tasks during games inherently differ between forwards and defensemen. Consequently, the distribution of fitness strategies should reflect the metabolic requirements specific for positional demands.
Forwards and defensemen both require a highly developed aerobic capacity due to the homogenous demand for oxidative recovery between shifts and periods. However, during a competitive season there may be key time periods when performing position specific fitness modalities are preferred (e.g. middle to late off-season/in-season breaks). This may be a greater focus on ATP-PC resynthesis and neuromuscular endurance capacity for forwards via repeated-sprint training protocols, (e.g. 5-10 seconds of all-out work with 25-50 seconds of rest) (21,22), due to the higher need for intense skating speeds separated by longer rest periods between shifts. Conversely, defensemen may benefit from a higher proportion of training that taxes a mix of anaerobic glycolytic and oxidative energy pathways such as high-intensity interval training, (e.g. 30-60 seconds of high-intensity work with 60-120 seconds of rest) (22), due to the longer duration and frequency of shifts performed at moderate to high intensities with reduced recovery periods between shifts.
About Ed
Ed Gannon is the head strength and conditioning coach of the Buffalo Sabres. Originally from Great Britain, he's been with the team since 2015.
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References
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