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Functional Performance Following an Ice Bag Application to the Hamstrings

Fischer, Jennifer1,2; Van Lunen, Bonnie L1,2; Branch, J David1; Pirone, Jamie L1

Journal of Strength and Conditioning Research: January 2009 - Volume 23 - Issue 1 - p 44-50
doi: 10.1519/JSC.0b013e3181839e97
Original Research

Fischer, J, Van Lunen, BL, Branch, JD, and Pirone, JL. Functional performance following an ice bag application to the hamstrings. J Strength Cond Res 23(1): 44-50, 2009-This study examined the immediate and short-term (20 minute) effects of 3- and 10-minute ice bag applications to the hamstrings on functional performance as measured by the cocontraction test, shuttle run, and single-leg vertical jump. Forty-two (25 women, 17 men) recreational or collegiate athletes who were free of injury in the lower extremity 6 months before testing and who did not suffer from allergy to cryotherapy were included. Time to completion was measured in seconds for the cocontraction and the shuttle run test. Single-leg vertical jump was measured on the Vertec (Sports Imports, Columbus, Ohio) in centimeters. The 10-minute ice bag application reduced immediate postapplication vertical jump performance and increased immediate post and 20-minute post shuttle run time (p ≤ 0.05). A decrease in cocontraction time was observed at 20 minutes post compared with preapplication during the control condition in which no ice bag was applied. Power and functional performance are affected by short-term cryotherapy application. Power and functional performance was impaired immediately and 20 minutes after 10-minute ice bag application to the hamstrings, whereas a shorter duration of ice application had no effect on these tasks.

1Department of Exercise Science, Sport, Physical Education, and Recreation and 2Sports Medicine Research Laboratory, Old Dominion University, Norfolk, Virginia

Address correspondence to Bonnie L. Van Lunen, bvanlune@odu.edu.

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Introduction

Various forms of cryotherapy application are used on a daily basis by clinicians and athletes to treat acute and chronic injuries. Cryotherapy, particularly the ice bag, has been widely accepted as a means to control inflammation, pain, and edema, to reduce spasticity, and to facilitate movement (9,27). The body's reaction to cryotherapy is vasoconstriction (28,41); therefore, the subsequent decrease in metabolism limits secondary hypoxic injury (26,28). The decrease in metabolism also affects the muscular (28,33) and nervous systems (28) by prolonging the action potential of the muscle fiber (27), slowing α-motor neuron conduction velocity (32,41), and reducing (34), increasing (9,37), or maintaining force production (15,48). Research has also demonstrated that muscular tissue temperature decreases after cryotherapy and continues to decrease even when the modality is removed (22,36,39,40,51). Primary factors that account for the amount of intramuscular temperature change include the temperature gradient between the agent applied and the body surface to which it is applied (3,5,29,31,35,38,47,50), the region and surface area over which the agent is applied (5,29,47,50), the duration of the treatment (5,29,31,35,38,47), and the depth at which the tissue temperature is measured (29,35,38,47). As a result, the contracting muscle previously exposed to cryotherapy may be at risk for injury because of these factors. Therefore, the well-established benefits of cryotherapy must be weighed against potential risks when considering return-to-play criteria.

In addition to the potential risk of injury, the effect of cryotherapy on functional performance is a relevant concern, especially if the athlete plans to return to practice or competition immediately after the treatment. Previous investigations of the effect of cryotherapy on isokinetic strength (10,18,19,24,25,33,46), and various functional performance tasks, such as the cocontraction test (14,16,30), carioca test (16), shuttle run (2,12,16,44), vertical jump (1,7,11-13,20,42,44), arm-pull weight lifting (49), and a 6-m hop test (6,12,43), have produced discordant results.

Different modes of cryotherapy application have also been examined, such as ice immersion (mainly of the lower leg), ice bag, and Cryocuff with varying application times ranging from 3 to 30 minutes (8,10,12,16,18,19,24,25,33,46,49). The effects of cryotherapy on skeletal muscle (10,18,46), joint (16), and a combination of both muscles and joints (8,12,19,24,25,33) have been studied using various techniques. Although many aspects of cryotherapy have been studied, the results of studies on lower-extremity functional performance have been controversial (1,2,6,7,11-14,16,20,30,42-44). Replication of various aspects of the current studies, with appropriate modifications, will help to examine the effect of different durations of ice bag application to the hamstrings and functional performance. Limited durations (3 and 10 minutes) of ice bag application need to be evaluated; these durations have not been widely studied in the previous literature because they are not typical ice bag treatment times. However, there are numerous occasions when an athlete removes an ice bag treatment that has been implemented and returns to play, and, therefore, the effects of limited treatment should be studied.

Many of the functional skills performed by an athlete involve the concept of cocontraction. The shuttle run (2,12,16), vertical jump (1,7,11-13,20,34), and the cocontraction test (14,16,30) engage the hamstrings at least as cocontractors, and, therefore, these tests are of interest because we have no information on how ice bag application to the hamstrings affects the outcome. The specific objective of this study was to investigate the immediate and short-term effects of 3 and 10 minutes of ice bag application to the hamstrings on functional performance as measured by the shuttle run, single-leg vertical jump, and the cocontraction test. We hypothesize that the 10-minute ice bag treatment will have an immediate effect on functional performance scores because there will be some cooling of the hamstring musculature, whereas the 3-minute application will have no effect because it will only cool superficially.

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Methods

Experimental Approach to the Problem

Subjects completed three trials of the three functional performance tasks (shuttle run time, cocontraction time, single-leg vertical jump) immediately before, immediately after, and 20 minutes after each of three durations of ice bag application to the hamstrings: control (no ice bag), 3 minutes, or 10 minutes. The order of ice bag application duration was counterbalanced with a washout period of at least 1 day between treatments. The order of functional performance task administration was also counterbalanced within each subject and across ice bag treatments. Separate 3 × 3 repeated-measures analyses of variance were used to assess each functional test.

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Subjects

Twenty-five women (age = 22 ± 0.5 years, height = 152 ± 1.9 cm, mass = 71 ± 2.4 kg) and 17 men (age = 23 ± 0.5 years, height = 170 ± 3.8 cm, mass = 85 ± 3.9 kg) intercollegiate or recreational athletes volunteered to participate in the study. The athletes participated in some form of organized athletics (practicing and playing sport for at least 2 hours, three to four times per week) and had prior experience in completing at least the vertical jump and shuttle run tests. The primary criterion for participation included no lower-extremity injury for at least 6 months before testing and no contradicting reaction to cryotherapy. Subjects completed all tests in the morning and were asked not to participate in any activity other than walking before the testing sessions. Procedures were approved by the university institutional review board before the beginning of the investigation. Subjects were informed of any possible risks associated with the study before giving their informed consent.

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Procedures

Subjects reported to the testing site on four different occasions (familiarization session, control with no ice bag application, 3-minute ice bag application, and 10-minute ice bag application), each separated by at least 1 day. During the familiarization session, all procedures were reviewed. The dominant leg, determined by asking each subject to jump off of one leg (as if shooting a basketball lay-up), was used for all treatment sessions. Each subject wore shorts, a T-shirt, and athletic shoes, completed a standardized 5-minute warm-up on a stationary bike, and performed a 30-second static hamstring stretch. Subjects assumed the prone position to receive all treatments. Ice bag treatments consisted of two plastic bags (28 × 46 cm) one-third filled with cubed ice placed on the hamstring muscle belly and secured with plastic wrap (manually secured) to ensure consistent placement across ice application treatments. During the control condition of no ice application, each subject remained prone for 10 minutes. Between the posttests, the subjects remained prone. The subjects completed three trials of each functional test, received the treatment, and completed an immediate posttest and a final posttest 20 minutes later. Control (no ice bag), 3-minute, and 10-minute ice bag application testing order was randomly assigned. Functional test order (shuttle run, cocontraction test, and vertical jump) was counterbalanced.

During each session, subjects completed three trials of the shuttle run, cocontraction test, and single-leg vertical jump. For the shuttle run test, two strips of tape were placed on the floor 6.1 m apart. Subjects were instructed to sprint to the line, touch it with their foot, and sprint back, twice, completing 24.4 m total. This test was recorded in seconds. Fleishman (17) reported the reliability of this test as r = 0.85.

The cocontraction test (14,16,30) (Figure 1) was performed by attaching one end of a heavy rubber tube (2.5-cm diameter, 1.23 m long; The Pro Unit, Pro Orthopedic Devices, Inc, Tucson, Arizona) to a nylon belt around the subject's waist and the other end to a hook mounted on a wall, 1.52 m up from the floor. A perpendicular line was drawn from the hook on the wall to the floor. The point where this line intersected with the floor served as the origin of a semicircle (2.44-m radius) drawn on the gymnasium floor. Subjects stood facing the hook with their feet along the outside of the semicircle, stretching the cord to twice its recoil length (2.44 m). Subjects were instructed to begin on the right side of the semicircle and complete five wall-to wall lengths using a shuffle step (three to the left, two to the right). This test was measured in seconds.

Figure 1

Figure 1

The single-leg vertical jump test was measured on the Vertec (Sports Imports, Columbus, Ohio). After measurement of the subject's standing reach, the subject was instructed to crouch on the test leg under the slivers of the Vertec. The subject then jumped as high as possible and pushed the slivers backward at the top of the jump. The difference between the subject's standing reach and his or her jump height was recorded in centimeters. The reliability for this test for college men has been reported as r = 0.98, and the validity as r = 0.99 (23).

The timed tests were started with the command “go” and ended when the subject's foot touched the end line or they reached the wall. A stopwatch, accurate to 0.1 seconds, was used to time the cocontraction test and the shuttle run. The accuracy of the Vertec is reported by the manufacturer to be ± 0.5 inches (21). Three trials of each test were performed during each testing session, and the mean was used for analyses. We allowed 45 seconds of rest between each trial and 1 minute of rest between each different functional test. Subjects were instructed to complete each test as quickly as possible, but no words of encouragement or knowledge of the results were offered during testing.

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Statistical Analyses

We initially included gender as a between-subjects factor and found main effects for gender for each test, but we failed to find any significant interactions, so we excluded it from the analysis. Therefore, the effects of ice application duration (3) and trial (3) on single-leg vertical jump, the cocontraction test, and the shuttle run were examined by separate, repeated-measures analyses of variance (SPSS 10.1 for Windows, Chicago, Ill) with α = 0.05 for main and interaction effects. Tukey's HSD was used for post hoc comparisons. Unless otherwise indicated, data are presented as mean ± SE.

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Results

Ice bag duration main effects for shuttle run (p = 0.399) and vertical jump (p = 0.080) were not significant, but a significant ice bag duration main effect was observed for the cocontraction test (p = 0.047), with the control group having the lowest time (11.130 ± 0.231 seconds) compared with either the 3-minute (11.265 ± 0.216 seconds) or 10-minute ice bag group (11.398 ± 0.240 seconds). Trial main effects for cocontraction time (p = 00.063), vertical jump (p = 0.507), and shuttle run (p = 0.529) were not significant.

As illustrated in Figures 2-4, the interaction between ice bag duration and trial was significant for all functional performance tasks. Shuttle run time increased immediately after the 10-minute ice bag application and 20 minutes posttreatment (p = 0.018, Figure 2). There was a significant decrease in cocontraction time for the control group at 20 minutes posttreatment compared with pretreatment (p = 0.014, Figure 3). Vertical jump height was significantly reduced immediately after the 10-minute ice bag application (p = 0.023, Figure 4). No other treatment conditions produced significant findings.

Figure 2

Figure 2

Figure 3

Figure 3

Figure 4

Figure 4

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Discussion

We hypothesized that both ice treatments would adversely affect the immediate postapplication measures because of the negative effect cryotherapy has on motor activity. The contractile properties of the muscle may be compromised because of decreased nerve conduction velocity and sensitivity of muscle spindles (28) and possible decreased capacity of the muscle to generate force (4,34) after decreases in tissue temperature. However, the key finding was that shuttle run and vertical jump performances were impaired immediately after 10 minutes, but not by 3 minutes of ice bag application. We also hypothesized that the adverse effects of 10 minutes of ice application would remain in effect for at least 20 minutes. Although 20-minute posttreatment cocontraction time and vertical jump were unaffected after 10 minutes of ice application, the finding that adverse effects of 10 minutes of ice application persisted in the shuttle run test lends partial support to our second hypothesis.

To our knowledge, this is the first study of the effect of cryotherapy on functional performance of the hamstrings. We chose to assess functional performance by using the shuttle run, single-leg vertical jump, and cocontraction test to mimic the stresses placed on the hamstrings during athletic competition. Previous studies have examined the effect of cryotherapy on isometric strength (8,34), isokinetic strength (10,18,19,24,25,33,46), and functional performance tasks (12,16,44,49). The studies that examined the effects of 20 minutes of ice immersion of the foot and ankle joint (16), the lower leg to the fibular head (12), and the quadriceps muscle (44) have yielded differing results, which leads us to examine the different functional tests used.

The shuttle run is a well-established field test for assessing agility. Our results are similar to those of Cross et al. (12) and Richendollar et al. (44), who have reported an immediate increase in shuttle run time after 20 minutes of ice immersion to the level of the fibular head and quadriceps muscle, respectively. However, Evans et al. (16) have reported no change in mean shuttle run time after a 20-minute ice immersion of the foot and ankle. Additionally, we detected a significant increase in shuttle run time to completion both immediately and 20 minutes after the 10-minute ice bag application to the hamstrings. The 10-minute ice bag application may have begun to affect the muscle tissue, whereas the 3-minute application only affected the superficial layer of skin. Our finding supports those of Cross et al. (12) and Richendollar et al. (44), in which it is thought that the negative influences of cryotherapy on muscle contractility and a decrease in nerve conduction velocity may explain the immediate detriment in performance. Our findings demonstrate that this detriment occurred not only immediately, but even 20 minutes later, which may lend support to the idea that agility tests may be affected for longer periods of time whereas single power moves, such as the vertical jump, may not be affected when short-term cryotherapy is applied.

Many researchers have also used the vertical jump as a test of functional performance (1,12,13,43); however, there has been an ongoing debate over use of the double-leg or the single-leg vertical jump for assessment purposes. The single-leg vertical jump is viewed as a test that more closely resembles the functional stresses placed on the body during athletic activities (12,45). The vertical jump primarily tests the anaerobic power of the hip, knee, and ankle extensors (12,21), which supports our rationale for testing the hamstrings by single-leg vertical jump. Our findings of a decrease in single-leg vertical jump height immediately after the 10-minute ice bag application are in agreement with those of others (12,13,44). However, at 20 minutes postremoval, no differences in jump height were found, potentially suggesting that 10 minutes of application are only enough to affect immediate performance. It has been found that vertical impulse does decline after 20 minutes of ice immersion to the lower leg (25), and vertical impulse represents force applied over time and indicates the accelerating force during a jump. More research is warranted to determine whether there is any effect on performance within the additional time periods (5,10, and 15 minutes) after immediate removal.

The cocontraction test (12,14,30) was chosen because the hamstrings and quadriceps are simultaneously activated, which simulates athletic stresses placed on the lower extremity. Ice bag application to the hamstrings did not produce significant findings as tested by the cocontraction test; however, we observed a nonsignificant increase in means for the immediate posttest measures after the 10-minute ice bag application. The control condition of no ice bag application showed significantly faster times, which we attributed to a lack of familiarization with the shuffling movements associated with the cocontraction test. Despite a familiarization session in which the subjects completed three trials of the test, the subjects still completed the test more efficiently with every trial. Evans et al. (16) used the cocontraction test after a 20-minute ice immersion of the foot and ankle and found the times were slightly slower, yet insignificant. They report that subjects completed four to six practice trials during the familiarization session, which could account for our conflicting results. We suggest that multiple familiarization sessions or more than three practice trials should be completed before using this test in future research. They also report slower and less variable cocontraction times than were found in our study. This may be attributable to their increased time of the cryotherapy session, and the body part chosen for treatment. The cocontraction test mimics aspects of the shuttle run in which power output and change of direction are involved; however, we believe that the test is a novel task and that the lack of a familiarization session affected the outcome.

Our study provides additional insight regarding the effect of cryotherapy on a major muscle group while performing functional activities. We wanted to provide clinical relevance to practicing certified athletic trainers; hence, we chose ice bag application because it is the most widely available form of cryotherapy. The time of application also coincides with the clinical relevance of the study. Our rationale for this includes circumstances in which the athlete will be returned to play after ice treatment of short durations. In some instances, an athlete will remove the ice bag early (within 10 minutes) and return him- or herself to play without clearance by a certified athletic trainer. We also examined the effect of these ice treatments after 20 minutes of time had elapsed; we found that as little as 10 minutes of ice can still detrimentally affect functional performance, as shown by the shuttle run in our study.

Our findings cannot be generalized to the use of cryotherapy as a therapeutic modality as part of a treatment or rehabilitation program; however, caution must be used by clinicians when returning athletes to activity after a 10-minute ice bag application to the hamstrings. As our study demonstrates, this treatment detrimentally affected the single-leg vertical jump and shuttle run test immediately after treatment. It also seems that a superficial cooling treatment of 3 minutes has no effect on the power output for these functional tests; therefore, it should not affect performance. Future research should evaluate the effects of these parameters on the injured population and/or the intramuscular temperature over time after ice bag application. In addition, the use of functional tests, specifically the cocontraction test, should be evaluated for reliability.

In conclusion, impaired functional performance in tasks involving the hamstrings were observed immediately and 20 minutes after 10-minute ice bag application in male and female athletes. The use of cryotherapy is an intriguing paradox for certified athletic trainers who need to apply ice to the hamstrings without compromising functional performance.

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Practical Applications

Certified athletic trainers, athletes, coaches, and practitioners often apply ice to an injured athlete during practice or games. There are often times when athletes feel that they are ready to go back into competition, and they do not complete the total application time for the cryotherapy session. Our findings suggest that a 3-minute application does not affect the functional test measures, but a 10-minute application affects vertical jump and shuttle run times. An athlete may not be able to perform at his or her optimal level after a 10-minute application of cryotherapy even though the cryotherapy was applied to a secondary muscle group; therefore, we should use caution in returning the individual back into competition because there may be other deficits that have not yet been identified. Further research is warranted on primary muscle groups and on the use of short-term cryotherapy applications.

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Keywords:

cocontraction; cryotherapy; vertical jump; shuttle run

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