Gradual decline in performance and changes in

Eur J Appl Physiol DOI 10.1007/s00421-012-2320-1

O R I G I N A L A R T I CL E

Gradual decline in performance and changes in biochemical parameters of basketball players while resting after warm-up Christos Galazoulas · Anastasia Tzimou · Georgios Karamousalidis · Vassilis Mougios

Received: 15 September 2011 / Accepted: 9 January 2012 © Springer-Verlag 2012

Abstract Warm-up is used before every competitive sporting activity as a means to activate the body, reduce the risk of injury and increase performance in subsequent tasks. However, there is little information on how long the eVects of warm-up last. This is of particular interest in basketball playing, since no rewarm-up is allowed to players who sit on the bench. Thus, the aim of this study was to examine changes in performance and biochemical parameters of basketball players while resting after warm-up. On each of four consecutive days, 14 elite basketball players (7 male and 7 female) performed a structured warm-up program, after which they had body temperature measured, provided blood samples and performed countermovement jump and 20-m run tests. Then, they rested for either 10, 20, 30 or 40 min in a random, counterbalanced order. Temperature measurement, blood sampling, and performance testing were repeated after each rest interval. Body temperature and countermovement jump decreased gradually during rest (p < 0.05 for linear trend), whereas 10- and 20-m run times increased gradually (p < 0.05 for linear trend). Serum glucose decreased during rest (p = 0.028) independent of interval duration. We conclude that there is a relatively fast decline in jumping and running performance when basketball players remain inactive after warm-up. Our study highlights the need to address the rapid drop in performance after warm-up for the basketball players who do not participate in a game from the start.

Communicated by Martin Flueck. C. Galazoulas (&) · A. Tzimou · G. Karamousalidis · V. Mougios Department of Physical Education and Sport Science, Aristotle University of Thessaloniki, Thessaloniki, Greece e-mail: [email protected]

Keywords Warm-up · Basketball · Glucose · Lactate · Sprint performance · Countermovement jump

Introduction The eVect of warm-up on subsequent sport performance has been investigated since the 1930s. There is widespread belief that warm-up before a sporting activity may improve athletic performance (Fradkin et al. 2010; Hedrick 1992; Shellock and Prentice 1985). This may be through variety of biomechanical, physiological and biochemical responses including increased muscle and tendon suppleness, elevated blood Xow to the muscles, acceleration of metabolic reactions and faster nerve conduction (Bishop 2003; Hedrick 1992; Shellock and Prentice 1985), as well as acceleration of the oxygen consumption response to subsequent exercise (Burnley et al. 2005; Hajoglou et al. 2005). Warm-up is also intended to reduce the risk of injury (Woods et al. 2007). Finally, it has been hypothesized that warm-up may confer a number of psychological eVects, such as increased preparedness (Bishop 2003). As such, warm-up precedes almost every athlete’s participation in a competitive event. Warm-up protocols are often supplemented by static or dynamic stretching routines. Studies have found static stretching to be detrimental to performance in sprint runs, jumps and other activities requiring strength (Behm et al. 2001; Fletcher and Jones 2004; Nelson et al. 2005; Young and Behm 2003), as opposed to dynamic stretching, which resulted in increased sprint running performance (Fletcher and Jones 2004). Direct comparison of the two stretching techniques showed that warm-up protocols including dynamic stretching produced higher sprint run and jump

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Eur J Appl Physiol Fig. 1 Summary of the study design. CMJ, countermovement jump

General warm-up Stretching Specific warm-up




Body temperature Blood sampling CMJ 20-m sprint run




10-min rest Body temperature Blood sampling CMJ 20-m sprint run

20-min rest 30-min rest Body temperature Blood sampling CMJ 20-m sprint run

performance than warm-up protocols including static stretching (Faigenbaum et al. 2005; Fletcher and MonteColombo 2010; Needham et al. 2009; Vetter 2007). Despite the nearly universal acceptance of the value of warm-up before athletic competition, there is surprisingly no information on how long the beneWcial eVects of warmup on performance last. Such information is crucial in basketball; according to regulations (FIBA 2010), a team may use 12 players in a game, of whom 7 must stay seated on the bench at all times, not being allowed to perform a rewarm-up right before the coach decides to use them, although it has been reported that athletes can respond better to maximal activities after a rewarm-up (Mohr et al. 2004). The question then arises, is there any point to athletes warming up if he or she is not scheduled to enter the game from the beginning? Thus, the aim of this study was to evaluate changes in performance and biochemical parameters of basketball players while resting after a typical warm-up protocol consisting of general warm-up, dynamic stretching and speciWc warm-up exercises.

40-min rest Body temperature Blood sampling CMJ 20-m sprint run


accordance with the Code of Ethics of the Aristotle University of Thessaloniki, the Helsinki declaration and the current Greek laws. Study design The study design is summarized in Fig. 1. On four consecutive days, the participants performed warm-up in an indoor basketball court followed immediately by measurement of body temperature, blood sampling and performance testing consisting of CMJ and 20-m sprint running. Then they rested for either 10, 20, 30 or 40 min in a random, counterbalanced order. The choice of this time frame was based on the facts that the duration of the Wrst half in a basketball game is approximately 40 min and that testing a resting period of less than 10 min would not have been relevant, as 10 min of real time correspond to only 3–4 min of game time. During resting the players remained seated on the bench and had access to water ad libitum. Subsequently, they were subjected to measurement of body temperature, blood sampling and performance testing as before.

Methods

Conditioning

Participants

One week before the experimental trials, three training units were conducted on consecutive days to familiarize the participants with the warm-up and testing procedures, as well as to test the experimental protocol. These sessions included the measurement of heart rate with a Polar FT40 heart rate monitor (Polar, Kempele, Finland), as it was our intention to examine the possible relationship between this parameter and changes in performance after the warm-up. However, heart rate had dropped to baseline already by 10 min of rest; therefore, its measurement was omitted from the main experiment.

The experiment began with eight male and eight female healthy, elite basketball players, aged 21–22, who volunteered to participate in the study. The players had been training in basketball for an average of 12 years and were playing in two semi-professional divisions (B and C) at the time of the study. All participants completed a health questionnaire and signed a consent form after being informed verbally and in writing about the aim, procedures and possible hazards of the study. All procedures were in

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Sprint run

Table 1 Characteristics of the participants (mean § SD) Men (n = 7)

Women (n = 7)

Age (years)

21.4 § 0.4

21.5 § 0.7

Body mass (kg)

78.6 § 9.1

64.6 § 8.6

Height (m)

1.84 § 0.06 1.72 § 0.10

Body mass index (kg/m2)

23.1 § 1.6

Resting heart rate (bpm) Resting systolic blood pressure (mmHg) Resting diastolic blood pressure (mmHg) Resting ear temperature (°C)

21.8 § 3.5

68 § 14

69 § 12

125 § 10

120 § 11

71 § 8

76 § 6

36.2 § 0.4

36.1 § 0.5

Experimental protocol The players were randomly assigned the order of rest intervals during the four experimental days. There were 24 possible orders of the four intervals, 16 of which were picked by a draw. On each day, each of the four intervals was assigned to two males and two females. However, one male and one female participant missed one experimental day and were excluded from the study. The characteristics of the remaining 14 players can be seen in Table 1. The players warmed up for a total of 27 min as they would do before a game. The warm-up protocol consisted of general warm-up lasting 7.5 min, dynamic stretching lasting 8.5 min, and speciWc warm-up lasting 11 min. The detailed program is presented in Table 2. Before warmup, immediately after it, and at the end of the rest interval, body temperature was measured in the ear with an infrared ear thermometer (TotiFar CT-30DX, OST, Jsinchu, Taiwan). Five milliliters of blood were drawn from a forearm vein into EDTA-containing test tubes at the end of the warm-up and 1–2 min before the end of the rest interval. Blood samples were kept on ice until they were transported to the laboratory (within 75 min from the initial sampling) where they were treated as described below. Immediately after blood sampling, the athletes were asked to perform two tests; the CMJ and the 20-m sprint running. Ambient temperature was 21–22°C during all test sessions. Countermovement jump The athletes rested their arms on the hips, bent the knees and, without pausing, jumped as high as possible. Three consecutive jumps were performed and were recorded through the use of a force plate (Newtest Powertimer 300 Oy, Finland). The highest jump was used in further analysis.

Performance at the 20-m sprint run with 10-m split time was used as an index of speed in basketball, as distances of 10–20 m are considered appropriate for testing sprint performance in basketball (Castagna et al. 2008; Drinkwater et al. 2008) and no previous training experience in or adaptation to the test is required (Moir et al. 2004; Spencer et al. 2004). Sprint run time was measured by photocells having an accuracy of 0.001 s (Newtest Powertimer 300 photocells IP67 Oy, Finland). The athletes started their attempts from a standing position 0.5 m behind the Wrst pair of photocells, as suggested by the manufacturer, to avoid the eVect of reaction time on performance. Two more pairs of photocells were placed, one at 10 m and another at 20 m from the Wrst pair. Participants were instructed to run as fast as possible. Biochemical analyses Twenty microliters from each blood sample that was transported to the laboratory were mixed with 200 l of 0.35 mol/l HClO4, and the hemolysate was stored at ¡80°C for the measurement of lactate. The rest of the blood was centrifuged at 1,500g for 5 min, and the resulting plasma was separated and stored at ¡80°C for the measurement of glucose. Plasma glucose was assayed through an enzymic photometric method by use of a kit from Spinreact (Girona, Spain). Blood lactate was assayed in the supernatant of the hemolysate described above (after centrifugation at 1,500g for 5 min) according to an enzymic photometric method from Sigma Diagnostics (St. Louis, MO, data sheet of product number L3916, lactic dehydrogenase). Dietary and hydration control Participants were instructed to eat a standardized breakfast 2–3 h before warm-up each day. Upon arrival at the basketball court, 1 h before warm-up, they were interviewed about what they had actually consumed. Dietary records were analyzed in Microsoft® Access through a food database created on the basis of published data (Food Standards Agency 2002). During the hour before warm-up, the players drank 1/2 liter of water. Then they drank another 1/2 liter during the half hour following the warm-up. Statistical analysis Results are reported as the mean § SD. The distribution of all dependent variables was examined by the Shapiro– Wilk test. Performance and biochemical parameters were initially analyzed by three-way ANOVA, that is,

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Eur J Appl Physiol Table 2 Warm-up protocol General warm-up (3 sets of 3 repetitions for each exercise) All players at the corners of a half-court start dribbling and Wnish with right hand lay-up at about 50% of maximal heart rate Likewise with left hand lay-up All players at the corners of a half-court start passing and Wnish with right hand lay-up at about 50% of maximal heart rate Likewise with left hand lay-up All players at the corners of a half-court start passing and Wnish with jump-shot at the right side at about 50% of maximal heart rate Likewise at the left side Dynamic stretching Walking high knee to chest: while walking, lift knee to chest and raise body on toes (2 sets of 10 repetitions on each leg) Leg swinging, antero-posterior direction: with one arm outstretched to the side and leaning against a wall, the opposing leg is stretched through full range of movement in the sagittal plane, undergoing both hip Xexion and hip extension (10 repetitions on each leg) Leg swinging, medio-lateral direction: with one arm outstretched to the side and leaning against a wall, the opposing leg is stretched through full range of movement in the coronal plane (side-to-side direction, 10 repetitions on each leg) Hurdler’s knee raise, forward movement: while moving forward, raise trailing leg and Xex hip (approximately 90°) in an abducted and externally rotated position, with the knee Xexed at 90°, then return to normal walking stride position (10 m) Hurdler’s knee raise, backward movement: same as above but moving backward Heel-ups: rapidly kick heels toward buttocks while moving forward (2 sets of 10 m) Tip-toe walking: moving forward while completing alternating plantar Xexion (tip-toe) with every step forward (2 sets of 10 m) High-knees run: emphasise knee lift and arm swing while moving forward quickly (2 sets of 10 m) Side stepping: move laterally while continually abducting leading leg and adducting trailing leg to replace foot placement of leading leg (2 sets of 10 m, each with diVerent leading leg) Cross-overs: similar to side stepping except that trailing leg travels past foot placement of leading leg and, in a sweeping motion, trailing leg alternates by crossing in front of and behind leading leg Skip-steps (high skips): while skipping, emphasise height, high knee lift and arm action (2 sets of 10 m) Zigzag running through ten cones placed in two parallel lines (Wve cones per line) with a stager of 2 m between them (20 m) SpeciWc basketball warm-up (3 sets of 3 repetitions for each exercise) All players at the corners of a half-court start dribbling and Wnish with right hand lay-up at 80–90% of maximal heart rate Likewise with left hand lay-up All players at the corners of a half-court start passing and Wnish with right hand lay-up at 80–90% of maximal heart rate Likewise with left hand lay-up All players at the corners of a half court start dribbling with a partner who slides with defensive steps

sex £ rest interval £ time with repeated measures on rest interval and time. This was a 2 £ 4 £ 2 design, in which the rest interval had four levels (that is, 10, 20, 30 and 40 min) and time had two levels (that is, before and after the rest interval). Because no sex-dependent response of any of the parameters to rest interval or time was found, the data from both sexes were combined to increase the power of the analysis and were analyzed by two-way ANOVA (4 £ 2, rest interval £ time, repeated measures on both factors). SigniWcant interactions were followed-up by simple main eVect analysis. Dietary intakes at breakfast on each of the four test days were analyzed by one-way ANOVA with repeated measures. Statistical signiWcance was declared at = 0.05. EVect sizes (ES) for main eVects, interactions and linear trends were estimated by calculating partial 2 using the SPSS v. 19. EVect sizes were classiWed as small (0.2), medium (0.5) or large (¸0.8).

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Results There were no diVerences in energy, carbohydrate, fat or protein intake at breakfast among days depending on rest interval. There were no injuries during warm-up or performance testing. Physiological responses Heart rate reached 178 § 7 bpm after warm-up (as determined in the conditioning sessions). Body temperature after warm-up and after each rest interval is presented in Fig. 2. Two-way ANOVA showed signiWcant main eVects of rest interval (p = 0.004, ES = 0.29) and time (p < 0.001, ES = 0.98), as well as an interaction of the two (p < 0.001, ES = 0.45). There was a gradual drop in temperature from an average 36.9°C after warm-up to 36.2°C after 40 min of rest, with linear trend (p = 0.012, ES = 0.40). Simple main

Eur J Appl Physiol

50

10 min

*

37.0

10 min

20 min

20 min

30 min

45

30 min

40 min

36.8

CMJ (cm)

Temperature (°C)

37.2

*

36.6 36.4

40 min

40

35

30

36.2

*

36.0 0

10

20

30

25

40

0

10

Time (min)

eVect analysis showed signiWcant diVerences between all pre-rest and the corresponding post-rest values (p < 0.001). Additionally, the values after the 10- and 20-min rest intervals, the 10- and 40-min rest intervals, and the 30- and 40min rest intervals diVered signiWcantly (p < 0.05) from each other.

30

40

Time (min) Fig. 3 Means and SD of countermovement jump height after warm-up and after each of the four rest intervals. Performance decreased after warm-up regardless of rest interval duration (p < 0.001) and with a linear trend as cool-down progressed (p = 0.016)

4.2

* 4.0

20-m Sprint (s)

Fig. 2 Means and SD of ear temperature after warm-up (zero time) and after the 10-, 20-, 30-, and 40-min rest intervals. Since the study was conducted over 4 days, during which the participants rested for a diVerent interval at a time, a diVerent baseline measurement was taken on each day. Because of this, there are four data points at zero time, each marked with a diVerent symbol corresponding to a diVerent rest interval. Each post-rest value diVered signiWcantly from the corresponding pre-rest value (p < 0.001). Additional signiWcant diVerences are indicated by asterisks (p < 0.05)

20

*

3.8

3.6 10 min 20 min

Performance

3.4

30 min 40 min

The CMJ values (Fig. 3) showed signiWcant main eVects of rest interval (p = 0.037, ES = 0.68) and time (p < 0.001, ES = 0.92). There was a linear drop in jumping performance as the athletes rested (p = 0.016, ES = 0.37 for linear trend) ranging, on average, from 13% at 10 min of rest to 20% at 40 min of rest. The 20-m sprint times are shown in Fig. 4. A main eVect of time (p < 0.001, ES = 0.84) and an interaction of rest interval and time (p = 0.006, ES = 0.27) were noticed. There was a linear increase in run time (therefore, a decrease in running performance) as the athletes rested (p = 0.008, ES = 0.43 for linear trend) ranging from 3.9% at 10 min to 6.3% at 40 min of rest. Simple main eVect analysis showed signiWcant diVerences between all pre-rest and the corresponding post-rest values (p < 0.001). Additionally, the value after the 40-min rest interval diVered signiWcantly from the values after the 10- and 20-min rest intervals (p < 0.05). Similar to the 20-m sprint times, the 0- to 10-m split times (Fig. 5) exhibited a main eVect of time (p < 0.001, ES = 0.85) and a rest interval-by-time interaction (p < 0.001, ES = 0.38). There was a linear increase in run

3.2 0

10

20

30

40

Time (min) Fig. 4 Means and SD of 20-m sprint run time after warm-up and after each rest interval. Each post-rest value diVered signiWcantly from the corresponding pre-rest value (p < 0.001). Additional signiWcant diVerences are indicated by asterisks (p < 0.05)

time as the athletes rested (p = 0.014, ES = 0.38 for linear trend) ranging from 5.0% at 10 min to 8.5% at 40 min of rest. Simple main eVect analysis showed signiWcant diVerences between all pre-rest and the corresponding post-rest values (p < 0.001). Additionally, the values after the 10and 40-min rest intervals diVered signiWcantly (p = 0.002). On the other hand, the 10-to-20-m split times (not shown) displayed only a main eVect of time (p = 0.016, ES = 0.37), reXecting an average increase by 3.4%. The increase in 0to 10-m split time after the rest intervals was signiWcantly higher than the corresponding increase in 10- to 20-m split time, both in absolute and relative terms (p < 0.01 by paired Student’s t test).

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*

2.4

10 min

2.2

10 min

2.0

20 min 30 min 40 min

1.8 0

10

20

30

40

Lactate (mmol/l)

10-m Sprint (s)

3.5

30 min

3.0

2.0

1.5

1.0 0

10

20

30

40

Time (min)

Fig. 5 Means and SD of 0- to 10-m split time in the 20-m sprint run after warm-up and after each rest interval. Each post-rest value diVered signiWcantly from the corresponding pre-rest value (p < 0.001). An additional signiWcant diVerence is indicated by asterisk (p = 0.002)

6.0

10 min 20 min

Glucose (mmol/l)

40 min

2.5

Time (min)

30 min

5.5

Fig. 7 Means and SD of the blood lactate concentration after warmup and after each rest interval. Asterisk signiWcantly diVerent (p · 0.05)

and 40 min of rest (p · 0.05) to a collective value of 1.64 § 0.71 mmol/l. When compared by testing day, the values after warm-up did not diVer signiWcantly, suggesting equality of warm-up between testing days.

40 min

Discussion

5.0

4.5

4.0 0

10

20

30

40

Time (min) Fig. 6 Means and SD of the plasma glucose concentration after warmup and after each rest interval. Values decreased after warm-up regardless of rest interval duration (p = 0.028)

Biochemical parameters The plasma glucose concentration after warm-up and after rest is shown in Fig. 6. There was only a signiWcant main eVect of time (p = 0.028, ES = 0.43) indicating a decrease from an overall post-warm-up value of 5.03 § 0.78 mmol/l to an overall post-rest value of 4.59 § 0.57 mmol/l, that is, by 9% on average. The blood lactate concentration (Fig. 7) showed signiWcant main eVect of time (p = 0.032, ES = 0.46) and interaction of rest interval and time (p < 0.001, ES = 0.57). Pairwise comparisons revealed a signiWcant increase from 2.15 § 0.85 mmol/l after warm-up to 2.52 § 0.81 mmol/l after 10 min of rest and signiWcant decreases after 20, 30

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20 min

In the present study, we have investigated changes in performance and biochemical parameters of male and female basketball players during 40 min of rest after a typical pregame warm-up, although we did not test whether warm-up increased performance, as doing so would be of little, if any, relevance (since, for athletes and coaches, not warming up is unthinkable of, at least for psychological reasons) and would risk injuring the athletes when performing maximal tests without warm-up. The relevance of the study lies in the fact that basketball players may sit on the bench for over 30 min before they are called in the game without being allowed to rewarm up. This poses the question as to whether warming up is at all useful to them if performance decreases quickly after warm-up. We could Wnd no study addressing this question for any sport, and this provided the impetus for the present investigation. We found that, indeed, there was a rapid and highly signiWcant performance decline in activities that are dominant in basketball (jumping and sprinting) while resting after warm-up, with large eVect sizes of 0.84–0.92. Moreover, this decrease was gradual (from 10 to 40 min of rest) with fairly uniform, small-to-medium, eVect sizes of 0.37–0.43 for linear trend. The decrease in performance was paralleled by a decrease in body temperature, with similar corresponding eVect sizes (0.98 for the eVect of time and 0.40 for the linear trend). The magnitude of the drop in CMJ

Eur J Appl Physiol

performance exceeded that in the 20-m sprint run performance, as the former ranged from 13% at 10 min after the end of warm-up to 20% at 40 min, whereas the latter ranged from 4 to 6% only. This suggests that ‘cooling-down’ may have a more severe impact on jumping rather than running performance. Of note is the apparent higher inXuence of cooling down on performance in the Wrst compared to the second half of the 20-m sprint run (5–8.5% gradual decrease vs. 3.4% decrease with no eVect of rest interval, respectively). Taken together, these diVerences in performance decrements may indicate that the greatest impact of cooling down was on tasks demanding explosive power, such as the vertical jump and the acceleration at the onset of sprinting. The observed rapid decrease in performance of the basketball players as time passed after warm-up may be related to the concomitant decrease in body temperature. In accordance with this, Mohr et al. (2004) found that the decrease in sprint running performance during the half-time of a soccer match was associated with the decline in body and muscle temperature during the same period and that rewarming up during the half-time was eVective in maintaining sprint running performance that was decreased while resting. The same authors proposed the dependence of neural transmission rate and speed of muscle contraction on temperature as possible mediators of the eVect of temperature on performance. As both these factors depend on ATP availability in the nervous system and muscles, it is possible that the decrease in body temperature aVected the rate of energyproducing reactions, which is quite reasonable from a biochemical point of view. Because explosive power production relies on high-frequency nerve impulses and on the ATP-phosphocreatine system in muscle, it is intriguing to speculate that either one or both were primarily aVected by the drop in muscle temperature. Future studies should enable exploring these possibilities. The decline in performance while resting after warm-up may be also linked to the drop in the plasma glucose concentration, although the size of it (0.44 mmol/l) was rather small. This hypothesis is supported by the studies of Welsh et al. (2002) and Winnick et al. (2005), who found that men and women with experience in sports such as basketball or soccer achieved shorter 20-m sprint time and higher jump height when their plasma glucose was maintained higher by carbohydrate ingestion compared to placebo. The authors hypothesized, and this is our hypothesis too, that a decrease in plasma glucose may have limited energy supply for highly demanding tasks to the nervous system. The drop in plasma glucose may be due to an imbalance between glucose supply by the liver and glucose uptake by the exercising muscles. In support of this, Wahren et al. (1973) have shown that, during 40 min of recovery from 40 min of moderate-intensity exercise, there was a rapid fall in

splanchnic glucose output from the elevated level maintained during exercise, concomitant with a rise in muscle glucose uptake, resulting in a drop in the blood glucose concentration. It should be noted that the decline in plasma glucose found in the present study can only be linked to the decline in performance overall, not its gradual nature, since no temporal trend was detected in the glucose concentration. Also, it should be noted that the players had only water during the hour before the warm-up and during rest after the warm-up. It would be interesting to examine whether carbohydrate intake during that period might alter the outcomes of this experiment. The blood lactate concentration exhibited a typical course of increase after exercise and decrease afterward. Because the intensity of warm-up was high in its Wnal part, it is conceivable that the peak of blood lactate was higher than the value of 2.52 mmol/l measured after 10 min of rest and that it occurred earlier. However, measuring the peak lactate concentration after warm-up was irrelevant to the current investigation. What is relevant is that the values measured at 10–40 min of rest were too low to account for the drop in performance (not to mention the fact that the values at 20–40 min were lower than the value immediately after warm-up). Thus, the observed changes in performance do not seem to be related to the blood (and, probably, muscle) lactate concentration. In summary, the main Wnding of the present study is that resting for 40 min after a typical warm-up protocol employed in basketball and consisting of general warm-up, dynamic stretching and speciWc warm-up exercises resulted in rapid, gradual loss of performance in two sport-speciWc skills, that is, vertical jumping and sprint running. The decline in jumping capacity was most severe, reaching 20% at 40 min of rest. The loss of performance may be linked to the concomitant drop in body temperature and the decrease in the plasma glucose concentration during resting after the warm-up. Our Wndings put into question the beneWts of warming up in basketball players who do not start the game. Possible solutions to the problem that warrant further investigation include a modiWcation of the rules to allow of the players who sit on the bench and carbohydrate intake before and after the warm-up. Similar suggestions may apply to other sports in which regulations do not allow rewarming up. Acknowledgments This work was supported by a donation from the Bodossakis Foundation. ConXict of interest interest.

The authors declare that they have no conXict of

Ethical standards The experiments described in the present work comply with the current laws of the country in which they were performed.

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