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Motor and Sensory Nerve Conduction Are Affected Differently by Ice Pack, Ice Massage, and Cold Water Immersion Esperanza Herrera, Maria C. Sandoval, Diana M. Camargo, Tania F. Salvini
Background. It is well known that reducing tissue temperature changes sensory and motor nerve conduction. However, few studies have compared the effect of different cold modalities on nerve conduction parameters.
Objective. The purpose of this study was to compare the effects of ice pack, ice massage, and cold water immersion on the conduction parameters of the sural (sensorial) and tibial motor nerves.
Design. An experimental study was conducted in which the participants were randomly assigned to 1 of 3 intervention groups (n�12 per group). Independent variables were cold modality and pre- and post-cooling measurement time. Depen- dent variables were skin temperature and nerve conduction parameters.
Methods. Thirty-six people who were healthy, with a mean (SD) age of 20.5 (1.9) years, participated in the study. Each group received 1 of the 3 cold modalities, applied to the right calf region for 15 minutes. Skin temperature and nerve conduc- tion parameters were measured before and immediately after cooling.
Results. All 3 modalities reduced skin temperature (mean�18.2°C). There also was a reduction in amplitude and an increase in latency and duration of the com- pound action potential. Ice massage, ice pack, and cold water immersion reduced sensory nerve conduction velocity (NCV) by 20.4, 16.7, and 22.6 m/s and motor NCV by 2.5, 2.1, and 8.3 m/s, respectively. Cold water immersion was the most effective modality in changing nerve conduction parameters.
Limitations. The cooling area of the ice massage and ice pack was smaller than that of the cold water immersion. The examiner was not blinded to the treatment group. The population included only participants who were healthy and young.
Conclusions. All 3 modalities were effective in reducing skin temperature and changing sensory conduction at a physiological level that is sufficient to induce a hypoalgesic effect. The results suggest that cold water immersion, as applied in this study, is the most indicated modality for inducing therapeutic effects associated with the reduction of motor nerve conduction.
E. Herrera, PT, MS, is a PhD stu- dent in the Program of Physiolog- ical Sciences, Federal University of São Carlos, São Carlos, Brazil, and Titular Professor, Department of Physical Therapy, Universidad In- dustrial de Santander, Ciudad Uni- versitaria, Carrera 27 Calle 9, Bu- caramanga, Santander, Colombia. Address all correspondence to Ms Herrera at: [email protected].
M.C. Sandoval, PT, PhD, is Associ- ate Professor, Department of Physical Therapy, Universidad In- dustrial de Santander.
D.M. Camargo, MS, is Associate Professor, Department of Physical Therapy, Universidad Industrial de Santander.
T.F. Salvini, PT, PhD, is Titular Pro- fessor, Department of Physical Therapy, Federal University of São Carlos.
[Herrera E, Sandoval MC, Ca- margo DM, Salvini TF. Motor and sensory nerve conduction are af- fected differently by ice pack, ice massage, and cold water immer- sion. Phys Ther. 2010;90:581–591.]
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Cryotherapy is the therapeuticapplication of a substance toremove body heat, resulting in diminished tissue temperature.1,2
It often is used in sports and rehabil- itation settings during the immediate and rehabilitative phases of injury management.3 Reduced tissue tem- perature, blood flow, and cellular metabolism are some of the physio- logical effects of cryotherapy.2– 8
Cryotherapy also reduces nerve con- duction velocity (NCV) in the sen- sory and motor nerves9,10 and has a controversial effect on muscle strength (force-generating capaci- ty).11–13 These physiological changes lead to some therapeutic effects such as a reduction in pain and mus- cle spasm and the prevention of posttraumatic edema.1–13
Various modalities are frequently used to deliver cryotherapy treat- ment. The efficacy of cooling de- pends on the method, application time, and treatment area and the in- dividual’s physical activity level im- mediately before or after the inter- vention.14 Overall, crushed ice pack, ice massage, and cold water immer- sion are considered the most effec- tive clinical modalities for reducing tissue temperature.14 –17 The efficacy of the cryotherapy modalities has been assessed by comparing their ca- pacity to decrease intramuscular,18
intra-articular,19 and skin tempera- ture10,14 –17,20,21 and to maintain the temperature changes. Skin tempera- ture measurement has been widely used because it is a simple and non- invasive procedure. Some authors,
based on skin temperature measure- ments, have hypothesized that skin temperature changes are closely re- lated to changes in subcutaneous and intramuscular temperature.10,15–17
However, the study by Jutte et al,22
which used a multiple regression model, showed that skin tempera- ture was a weak predictor of intra- muscular temperature because it explained only 21% of temperature variance within the muscle. The in- fluence of subcutaneous and muscu- lar tissue thickness on the cooling of deeper tissues also has been debated.23,24
A more precise way of analyzing the efficacy of cryotherapy modalities would be to compare their effects on deep tissues directly associated with clinical intervention using quantita- tive, direct, and reliable measure- ment. For example, nerve fibers are targeted for cryotherapy interven- tion to reduce muscle pain and spasm,3 and the changes attributed to cooling can be identified through nerve conduction studies (NCS) in which reliability has been estab- lished previously.25
Prior electrophysiological studies have determined a direct linear rela- tionship between skin temperature and NCV and an inverse relationship with latency, amplitude, and dura- tion of compound action poten- tial.26 –30 Nevertheless, this relation- ship varies according to the type of nerve fiber. Sensory nerves can show a reduction of 1.4 to 2.6 m/s for every degree of skin temperature re- duction, whereas motor NCV can de- crease by 1.1 to 1.5 m/s/°C.1 There are other factors that affect the rela- tionship between skin temperature and NCV, such as the depth of the nerve, the amount of surrounding subcutaneous tissue, age, range of temperature variation,27–30 and pos- sibly the type of modality used to alter skin temperature.
In the literature, there is a lack of studies comparing the effects of the different cold modalities on motor and sensory nerve conduction pa- rameters. We found only one study31
that established a greater effect of cold packs compared with gel packs on reducing ulnar motor NCV. How- ever, this study did not analyze the effect of these modalities on sensory nerve conduction. Therefore, it is important to compare the effective- ness of the different cryotherapy mo- dalities on motor and sensory nerve conduction to provide physiological parameters that contribute to the in- dication of the most adequate modal- ity according to the desired thera- peutic effect.
Considering that each cold modality has a different capacity to cool the skin and subcutaneous tissues and that nerve fiber conduction is af- fected by skin temperature changes, the hypothesis of this study was that cryotherapy protocols with different characteristics should have different effects on sensory and motor nerve conduction. The purpose of this study was to compare the effects of 3 commonly used therapeutic cold modalities (ice pack, ice massage, and cold water immersion) on the conduction parameters of the sural nerve and tibial motor nerve in par- ticipants who were healthy.
Method Research Design An experimental study was con- ducted with 3 randomly assigned in- tervention groups. The independent variables were cold modality type (ice pack, ice massage, and water immersion) and measurement time (pre- and post-cooling). The depen- dent variables were skin tempera- ture (degrees Celsius) and nerve con- duction parameters: NCV (meters per second), latency and duration (milli- seconds), amplitude of compound muscle (millivolts), and sensory ac- tion potentials (microvolts).
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582 f Physical Therapy Volume 90 Number 4 April 2010
Participants The participants were informed of the experimental procedures and the risks involved with the study and signed a consent form. Thirty-six participants who were healthy (18 women and 18 men) were enrolled in this study. The participants’ mean (SD) age, mass, height, and body mass index were 20.5 (1.9) years, 60.2 (8.4) kg, 1.63 (0.1) m, and 22.4 (1.6) kg/m2, respectively.
The sample size for each cold modal- ity group was determined through the application of the sampsi com- mand of Stata 9.0 software.* The fol- lowing design specifications were taken into account: ��.05; (1� �)�0.9; ratio�1:1; and method of calculation�analysis of covariance (ANCOVA) for repeated measure- ments, with a baseline measurement and a final measurement. The corre- lation between the initial and final measurements was r�.2. This method defined a sample of 10 to 12 participants for each cold modality group.
All participants filled out a health questionnaire that indicated the presence of any of the following ex- clusion criteria: history of alcoholism or smoking, peripheral vascular or cardiovascular disease, diabetes, neurological or skeletal muscle dis- orders, recent trauma or injury to the right leg, local hot or cold insensitiv- ity, cold adverse reactions, Raynaud phenomenon, and pregnancy. Addi- tionally, the participants were asked to avoid eating and drinking any stimulants (eg, alcohol, caffeine, chocolate) 2 hours before the inter- vention and to not exercise for at least 4 hours before intervention. These exclusion criteria and recom- mendations were considered accord- ing to previous studies.10,31
Instruments Skin temperature was measured us- ing an infrared thermometer (Raytek ST PRO†) that displays a precision of 1°C, high reliability (intraclass cor- relation coefficient�.97), validity (r� .92), and responsiveness (change in- dex�4.2). Nerve conduction measure- ments were acquired using a Nicolet Compass Meridian System‡ and stan- dard surface electrodes from the same manufacturer. The selection of cold modalities was based on their high effectiveness in reducing skin temperature and their frequent ap- plication in the clinical setting.14 –17
The ice pack consisted of 279 g of crushed ice in a plastic bag of 18 � 8 cm without air. Ice massage was ap- plied by using an ice block of 279 g with dimensions of 8 � 10 � 5 cm. Water immersion was conducted in an acrylic container of 20 � 35 � 30 cm, filled with water and crushed ice until the water temperature reached approximately 10°C, as reported pre- viously.17,20 The temperature of this modality was measured throughout the intervention, showing an initial mean of 8.9 (1.0)°C and a final mean of 7.8 (1.2)°C.
Procedure The participants were randomly as- signed to 1 of 3 cold modality groups by using a computer-generated ran- dom number sequence.32 Further- more, to minimize the influence of the circadian cycle on body temper- ature regulation, all participants re- ceived the cold modality at the same time (eg, 2– 6 PM). The intervention and measurement procedures were performed on the right calf of each participant. Given that the post- cooling measurement had to be taken immediately after the cold modality application, the same room was used for the application of inter-
vention and for the measurement procedures. Room temperature was maintained at 24 (0.08)°C, and there were no significant variations during the tests (P�.29).
Before the experimental protocol, the participants were asked whether they had followed the recommenda- tions regarding stimulant intake and exercise. Their height and weight were recorded to calculate the body mass index. The participants wore T-shirts and shorts and, for acclima- tization, assumed the prone position on the standard examining table for 15 minutes. During the acclimatiza- tion time, the treatment area to be cooled was determined and the elec- trodes for NCS were placed.
Cold modalities. The cold modal- ities were applied for 15 consecutive minutes by the same trained physical therapist (M.C.S.). This duration is frequently used for treatments be- cause it is sufficient to achieve ther- apeutic effects and it avoids compli- cations from cold modalities.21,33
The ice massage and the ice pack were applied to a previously deter- mined rectangular area (18 � 8 cm) on the calf (Fig. 1). The ice pack was applied directly to the skin and with- out compression. The ice massage was applied by continuous longitudi- nal displacements. For the cold wa- ter immersion, the participants re- mained seated while immersing the right leg as far as the top border of the rectangle determined for the pre- vious modalities (Fig. 1). At the end of intervention, the leg was quickly dried without friction, and the par- ticipant returned to the prone posi- tion for the post-cooling measure- ment. All participants completed the experimental protocols without ad- verse reactions to the cold.
Skin temperature measurement. Skin temperature was measured im- mediately before (pre-cooling) and after (post-cooling) the cold modal-
* StataCorp LP, 4905 Lakeway Dr, College Sta- tion, TX 77845.
† Raytek Corp, 1201 Shaffer Rd, Santa Cruz, CA 95061. ‡ Nicolet Biomedical Co, 5225 Verona Rd #2, Fitchburg, WI 53711-4497.
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April 2010 Volume 90 Number 4 Physical Therapy f 583
ity application. The temperature was measured at the center of the previ- ously defined rectangle (Fig. 1) with an infrared thermometer placed in a perpendicular position and kept as close as possible to the skin without touching.
Nerve conduction measurement. Compound action potentials result- ing from stimulation of the posterior tibial motor and sural nerves were recorded twice, before and after cooling, according to standardized techniques described by Oh.34 These
nerves were selected because they are located within the treatment area. Furthermore, the posterior tib- ial nerve has a high quantity of motor fibers, and the sural nerve is a pure sensory nerve,26,34 allowing the as- sessment of the cooling effects in both motor and sensory fibers.
Nerve conduction studies were ob- tained by the same examiner (E.H.). In order to reduce technical varia- tions, the stimulation and record- ing sites were delimited with a permanent ink marker during the
pre-cooling measurement, and the recording electrodes were not re- moved during the intervention, ex- cept in the participants who re- ceived cold water immersion. In this case, the recording electrodes were removed after the pre-cooling mea- surement and replaced at the sites previously marked for the post- cooling measurement.
Before the NCS measurement, the participants were instructed to avoid leg movements. The sural nerve re- cordings were obtained with a bandwidth of 20 Hz to 3 kHz, a gain of 20 �V per division, and a sweep speed of 1 millisecond per division. The surface bar recording electrode was placed immediately behind the lateral malleolus and the stimulat- ing electrode, was placed about 14 cm proximal to the active re- cording electrode, just lateral to the midline of the width of the calf mus- cle34 (Fig. 2A). Stimuli were 100- microsecond rectangular pulses, with amplitude adjusted slightly higher than needed to ensure a maximum response. The nerve signals were ob- tained by averaging 20 responses. The following sensory nerve param- eters were measured: NCV, peak la- tency, peak-to-peak amplitude, and duration (onset to end of negative wave) of the compound sensory ac- tion potential.
The tibial motor nerve recordings were obtained with a bandwidth of 2 Hz to 10 kHz, a gain of 2 mV per division, and a sweep speed of 2 mil- liseconds per division. The active disc recording electrode was placed over the abductor hallucis muscle, and the reference disc recording electrode was placed at the base of the big toe. The ground electrode was positioned on the calf muscle. The distal stimulation site was on the ankle immediately behind the medial malleolus, and the proximal stimula- tion site was on the knee on the medial aspect of the knee crease34
Figure 1. Cooling area. Ice pack and ice massage were applied to the same rectangular area defined according to the following procedure: (a) measurement of the length of the leg between the head of the fibula (1) and the lateral malleolus (2); (b) definition of the midpoint between the head of the fibula and the lateral malleolus (3); (c) projection of a perpendicular line to the posterior part of the leg, marking the midpoint of the calf (4); and (d) placement of the center of an acetate mold in the midpoint of the calf to mark a rectangle (18 � 8 cm) where the ice pack and ice massage would be applied. For the cold water immersion, the participants immersed their right leg in a cold water tank as far as the top border of the rectangle (5).
Figure 2. Stimulation and recording electrode sites for the sural nerve and tibial motor nerve conduction studies. (A) Sural nerve: antidromic technique was performed. (B) Tibial motor nerve: distal stimulation on the medial malleolus and proximal stimulation on the medial aspect of the knee crease (not shown). S�stimulation site, R�recording site, and G�ground electrode.
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(Fig. 2B). The following motor nerve parameters were measured: NCV for the nerve segment between an- kle and knee, distal latency, ampli- tude, and duration of the negative wave of the compound muscle ac- tion potential.
Intrarater reliability of sural and tibial motor NCS. Before data col- lection, we assessed intrarater reli- ability of the tibial motor and sural nerve recordings in 20 participants following the same recording tech- niques described above. The same examiner who performed the assess- ments of the current study tested each participant twice on 2 separate days with a minimum 8-day lapse be- tween the measurements.25
Statistical Procedures Intrarater reliability of nerve conduc- tion parameters was evaluated using the Bland-Altman method.35 Data were reported as mean difference (95% limits of agreement). For the present study, descriptive statistics were used to summarize the charac- teristics of the population, the skin temperature, and nerve conduction data, which are presented as mean (SD). The baseline characteristics of the cold modality group participants were compared using analysis of variance (ANOVA) and a chi-square test, depending on the scale of mea- surement of each variable.32 The measurements obtained before and after cooling were compared using a paired t test because the normal dis- tribution of all variables was proven by the Shapiro-Wilk test.32,36 In addi- tion, an ANCOVA37 compared the ef- fects of the 3 modalities of skin tem- perature and the nerve conduction parameters using the ice massage group as reference. For the statistical analysis, the Stata 9.0 software was used, with a significance level of ��.05.
Results Intrarater Reliability of NCS The intrarater analysis showed mean differences close to zero, and there was no evidence of systematic error. The mean differences (95% limits of agreement) for the sural nerve pa- rameters were: latency�0.17 milli- second (�0.73, 1.07), NCV��0.07 m/s (�4.48, 4.33), amplitude��2.9 �V (�20.73, 14.95), and dura- tion�0.04 millisecond (�0.3, 0.37).25 Respective data for the tibial motor nerve parameters were: laten- cy�0.23 millisecond (�1.10, 1.56), NCV��0.32 m/s (�6.20, 5.53), am- plitude��0.1 mV (�4.30, 4.10), and duration�0.36 millisecond (�0.91, 1.63) (unpublished data).
Effects of Cold Modalities on Skin Temperature and Nerve Conduction Parameters A total of 39 potential participants were assessed for eligibility; 2 did not meet inclusion criteria, and 1 was not assisted to the experimental session. Twelve participants were randomly allocated to each experi- mental group (Fig. 3). There were no significant differences in baseline characteristics among the cold mo- dality group participants (P�.05) (Tab. 1). There was a decrease in skin temperature after the applica- tion of the 3 modalities (P�.0001) (Tab. 2). The ice massage caused a greater decrease in skin temperature compared with the ice pack (��3.03, P�.001) and the cold wa- ter immersion (��9.36, P�.0001). All 3 modalities induced an increase in latency and duration of the com- pound action potential of the sural and tibial motor nerves (P�.05). There also was a reduction in the amplitude of the potentials and the NCV (P�.05) (Tabs. 3 and 4). The effect of the cold water immersion on all motor nerve parameters, as well as on amplitude and duration of sural nerve potential, was different and greater compared with the ef- fect of ice massage (Tab. 5). There
were no differences between the ef- fects of the ice pack and ice massage on the motor and sensory conduc- tion parameters (P�.05) (Tab. 5).
Discussion The 3 cold modalities resulted in sig- nificant changes in every sural nerve parameter, except cold water im- mersion in amplitude (Tab. 4). Mean differences among parameters deter- mined before and after cooling were greater than those determined in the intrarater reliability analysis. The effects of ice massage and ice pack on the tibial motor nerve parameters were more subtle (Tab. 3). Although latency and duration differences were statistically significant for the effect of ice pack intervention on the tibial motor nerve, mean differences were lower or similar to those deter- mined in the intrarater reliability analysis for this nerve. However, it is important to note that assessments after ice pack and ice massage pro- tocols did not require the removal of electrodes, which usually is the main source of error in NCS. Mean differ- ences in tibial motor nerve parame- ters from cold water immersion were greater than those determined in the intrarater reliability analysis. Therefore, we believe that the motor and sensory nerve conduction changes determined for each modal- ity were a real consequence of cool- ing rather than error in measurement methods.
The results of this study support the proposed hypothesis because the cold modalities applied have differ- ent effects on motor and sensory nerve conduction. The modality of cold water immersion, as applied in this study, had the greatest effect on the conduction parameters, espe- cially of the tibial motor nerve (Tab. 5). The modalities of ice pack and ice massage, as applied in this study, differed substantially from the cold water immersion. First, the ice massage and ice pack were applied
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April 2010 Volume 90 Number 4 Physical Therapy f 585
to the same calf area (44 cm2), whereas the area/volume covered by cold water immersion was much greater, including the calf, ankle, and foot regions where the nerve be- comes more superficial and thus
more susceptible to cooling. Second, these modalities also have thermo- dynamic differences: in the ice mas- sage and ice pack modalities, heat exchange occurs by conduction, whereas cold water immersion in-
volves conduction and convection processes.1 Our results can be ex- plained mainly by the differences in the area/volume, and this parameter of the cold modalities may contrib- ute to a greater cooling effect on the
Figure 3. Flow of participants through the study.
Table 1. Demographic Characteristics of the Participantsa
Variable
Intervention Group
Ice Massage (n�12)
Ice Pack (n�12)
Cold Water Immersion (n�12) P
Age (y) 19.7 (1.3) 20.7 (1.3) 20.9 (2.6) .26
Female participants, n (%) 5 (41.7) 6 (50) 7 (58.3) .72
Height (m) 1.61 (0.1) 1.64 (0.1) 1.65 (0.1) .54
Mass (kg) 58 (7.1) 60.4 (8.6) 62.1 (9.7) .51
Body mass index (kg/m2) 22.2 (1.6) 22.3 (1.4) 22.6 (1.7) .81
a Data are presented as mean (SD), except for the number and percentage of female participants.
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subcutaneous tissues, including the peripheral nerve. Future studies are needed to compare the effects of the cold modalities on nerve conduction with different thermodynamic prop- erties applied to an area of similar magnitude.
Paradoxically, cold water immersion was the modality that caused the least skin temperature reduction (Tab. 2), possibly due to the fact that a greater area received the treat- ment, leading to a faster activation of the thermoregulatory responses that protect the body from abrupt tem- perature changes.38 Consequently, skin temperature was quickly stabi- lized and did not adequately reflect the effects of cooling on subcutane- ous tissues.22
The cooling induced by the 3 modali- ties was effective in reducing the NCV and prolonging the latency and dura- tion of the compound muscle and sen- sory action potentials (Tabs. 3 and 4). The effects of temperature reduction on nerve conduction parameters are well described in the literature27–30
and may result from the changes in the structure of the axonal membrane39
and from the conductance of the voltage-sensitive sodium and potas- sium channels.27 Therefore, the cold reduces the nerve membrane current, which lengthens the refractory peri- ods following a stimulus; as a result, the duration of the nerve action poten- tial increases and the rate of impulse transmission decreases.
In the scientific literature, the rela- tionship between the amplitude of compound action potential and tem- perature remains a controversial is- sue. Some studies that analyzed the effect of temperature changes on conduction parameters showed a negative relationship,40,41 whereas other authors did not identify this relationship.27 In the present study, cold water immersion significantly reduced the amplitude of compound muscle action potential (Tab. 3). Similarly, the ice massage and the ice pack reduced the amplitude of sen- sory compound action potential (Tab. 4). Perhaps the differences be- tween the results of the present study and those of previous stud- ies27,40,41 are due to the differences in the skin temperature changes. In previous studies,27,40,41 skin temper- ature decreased only from 33.6°C to 22.5°C, whereas in the present study, the cooling induced by all modalities was greater (from 31.6°C to 4°C).
The amplitude of the compound ac- tion potential represents the number of nerve fibers that responds to an appropriate electrical stimulus.34
Therefore, the reduction of this pa- rameter after the cold modality appli- cation could suggest an increase in the activation threshold of some nerve fi- bers, as well as a block of the fibers that are more sensitive to cooling. Ad- ditionally, the increase in the duration of the compound action potential is an indicator of alteration in the discharge synchronization of nerve fibers.34
The physiological mechanisms of the hypoalgesic effect of cryotherapy have not yet been completely eluci- dated. Different hypotheses have been proposed: (1) closing of the pain gate, (2) counter-irritant effect that activates inhibitory control mechanisms, (3) increase in the acti- vation threshold of nociceptors, and (4) participation of descending path- ways of the central nervous system that modulate pain by releasing en- dogenous opiates. It also has been suggested that the hypoalgesic effect of cryotherapy could be related to an increase in pain threshold and pain tolerance associated with a decrease in NCV.9 We suggest that the inacti- vation of some nerve fibers, which is evident in the decrease in compound action potential amplitude, as well as the change in the synchronization response of these fibers could be other important physiological mech- anisms for the hypoalgesic effect of cryotherapy. Studies are needed to investigate this hypothesis.
Although the present study did not include specific pain measurements, the results for the 3 modalities sug- gest that the hypoalgesic effect of cryotherapy may be produced mainly by the reduction in sensory fiber conduction because the cool- ing effect on the conduction param- eters was usually greater in the sen- sory nerve than in the motor nerve (Tabs. 3 and 4). Ice massage, ice pack, and cold water immersion re- duced sural NCV by 37.9%, 31.9%,
Table 2. Skin Temperature in Participants Submitted to Different Cold Modalitiesa
Intervention Group
Skin Temperature (°C)
Pre-Cooling Post-Cooling Differenceb
Ice massage 31.58 (1.07) 3.98 (1.15) �27.6 (1.32)c
Ice pack 31.12 (2.13) 6.68 (3.4) �24.43 (2.87)c
Cold water immersion 31.55 (0.89) 13.32 (1.33) �18.23 (1.46)c
a Data are presented as mean (SD). b Difference�post-cooling � pre-cooling. c P�.0001.
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April 2010 Volume 90 Number 4 Physical Therapy f 587
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Cold Modalities and Nerve Conduction
588 f Physical Therapy Volume 90 Number 4 April 2010
and 41.8%, respectively. In contrast, these modalities reduced tibial mo- tor NCV by only 5.0%, 4.2%, and 17.0%, respectively. It is difficult to compare these results with those of previous studies9,31 because of the different intervention protocols and analyzed nerves. Algafly and George9
applied an ice pack for a mean time of 26 minutes and obtained a skin temperature of 10°C and a 33% re- duction in sensory plantar NCV. McMeeken et al31 used an ice pack for 15 minutes and obtained a skin temperature of 5.6°C and an approx- imate reduction of 13% in ulnar mo- tor NCV. Even though these studies measured different nerves, in a broad sense they corroborate the results of the present study, which demon- strated a greater cooling effect on the sensory fibers than on the motor fibers. The greater sensibility of the sensory fibers to cooling may be due to their more superficial location compared with the motor fibers, which would explain why the func- tional effects of cryotherapy on sen- sibility42 are more pronounced than the effects on muscle function.12
The depression of sensory and motor NCV derived from cooling modalities also may indicate the risks of delete- rious effects associated with pro- longed icing, such as skin burn and superficial nerve damage. Previous studies33,43 have shown cases of nerve palsy resulting from ice appli- cation near the subcutaneous course
of nerves. The consequent disability was transient (1– 4 days) or pro- longed (4 – 6 months), with all pa- tients eventually reaching full recov- ery. The application of cryotherapy is typically safe and beneficial if the protocol is appropriate and suffi- ciently monitored. However, clini- cians must be aware of the location of major peripheral nerves, the thick- ness of the overlying subcutaneous fat, the method of application, the duration of tissue cooling, and the surface area covered.33,43
The results of the comparison of the effects of the 3 cold modalities on conduction parameters show that the cold water immersion protocol used in this study, although neither the most comfortable modality for the participant nor the easiest to ap- ply, may be the most indicated for greater therapeutic effect mediated by the change in motor conduction (eg, in muscle spasm and spasticity [hypertonicity]). In contrast, the hy- poalgesic effect could be induced by any of the 3 assessed modalities. Cold water immersion was more ef- ficient in changing some parameters of sensory conduction, but the appli- cation of the 3 modalities lowered skin temperature to less than 13.6°C and reduced NCV by more than 10%. As suggested in previous stud- ies,10,17 these changes could be asso- ciated with the hypoalgesic effect of cryotherapy.
The present study had some method- ological limitations that restrict the generalization of the results. The cooling area of the ice massage and ice pack was small compared with that of the cold water immersion and possibly smaller than those used in the clinical setting. The study sample comprised only young participants who were healthy, and the responses might have been different in older adults and individuals with clinical dis- orders. The time used for each modal- ity (15 minutes) also may have been insufficient to induce greater effects on the motor nerve, especially in the case of the ice pack and the ice mas- sage, which were applied to restricted areas. Considering that the nerve con- duction evaluations were taken imme- diately before and after the cold mo- dality application, the examiner was not blinded to the treatment group. This fact may limit the internal validity of the study. Subsequent studies are needed to determine the functional relevance of changes in nerve conduc- tion induced by the cold modalities on sensibility and muscle strength, as well as the clinical importance of these changes. The present study contrib- utes to the literature because, to our knowledge, it is the first study compar- ing the effect of 3 modalities fre- quently used in clinical practice on the parameters of motor and sensory nerve conduction.
Table 5. Effects of Cold Modalities on Nerve Conduction Parameters (Analysis of Covariance, Using the Ice Massage Group as Reference)
Parameter
Tibial Motor Nerve Sural Nerve
Ice Pack Cold Water Immersion Ice Pack Cold Water Immersion
Coefficient (�)
Probability (P)
Coefficient (�)
Probability (P)
Coefficient (�)
Probability (P)
Coefficient (�)
Probability (P)
Latency 0.03 .87 3.23 �.0001 �0.54 .08 0.50 .09
Nerve conduction velocity
0.39 .51 �6.02 �.0001 3.18 .12 �2.11 .29
Amplitude 0.65 .47 �2.08 .022 5.43 .15 24.16 �.0001
Duration 0.04 .92 2.84 �.0001 0.02 .73 1.22 �.0001
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April 2010 Volume 90 Number 4 Physical Therapy f 589
Conclusions Ice massage, ice pack, and cold wa- ter immersion were effective in re- ducing skin temperature and chang- ing most of the motor and sensory conduction parameters, with greater effects on the sensory nerve. Cold water immersion, as applied in this study, was the most effective modal- ity in changing nerve conduction, especially in the tibial motor nerve. Our results can be considered clini- cally relevant and contribute to the informed choice of a cryotherapy modality based on the desired phys- iological and therapeutic effects.
All authors provided concept/idea/research design, writing, and consultation (including review of manuscript before submission). Ms Herrera and Dr Sandoval provided data collection. Ms Herrera, Dr Sandoval, and Ms Camargo provided data analysis. Ms Herrera provided project management and partici- pants. Dr Salvini provided facilities/equipment.
The study protocol was approved by the In- stitutional Ethics Committee of Universidad Industrial de Santandar. The study followed the Declaration of Helsinki.
Ms Herrera acknowledges Coordenação de Aperfeiçoamento de Pessoal de Nı́vel Supe- rior (CAPES, Brazil) for providing her doc- toral grant.
This article was received April 22, 2009, and was accepted December 6, 2009.
DOI: 10.2522/ptj.20090131
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