Intramuscular Temperature Changes During and After 2 Different

[
research report
]
KIMBERLY A. RUPP, MEd, ATC1 • DANIEL C. HERMAN, MD, PhD2 • JAY HERTEL, PhD, ATC3 • SUSAN A. SALIBA, PT, PhD, ATC4
Intramuscular Temperature Changes
During and After 2 Different Cryotherapy
Interventions in Healthy Individuals
C
ryotherapy is a commonly used treatment modality in acute
musculoskeletal trauma and pain. Physiological changes
occur both during and after cryotherapy treatment. Some
of these changes are well reported in the literature, such as
control of secondary hypoxic injury and edema,16 decreased skin12,13
and muscle5,15,17 temperature, decreased nerve conduction velocity,1,8
increased pain threshold and tolerance,1 and reduced pain.3,24
TTSTUDY DESIGN: Crossover.
TTOBJECTIVES: To compare the time required to
decrease intramuscular temperature 8°C below
baseline temperature, and to compare intramuscular temperature 90 minutes posttreatment,
between 2 cryotherapy modalities.
TTBACKGROUND: Cryotherapy is used to treat
pain from muscle injuries. Cooler intramuscular
temperatures may reduce cellular metabolism and
secondary hypoxic injury to attenuate acute injury
response, specifically the rate of chemical mediator activity. Modalities that decrease intramuscular
temperature quickly may be beneficial in the
treatment of muscle injuries.
TTMETHODS: Eighteen healthy subjects received
2 cryotherapy conditions, crushed-ice bag (CIB)
and cold-water immersion (CWI), in a randomly
allocated order, separated by 72 hours. Each condition was applied until intramuscular temperature
decreased 8°C below baseline. Intramuscular
temperature was monitored in the gastrocnemius,
1 cm below subcutaneous adipose tissue. The primary outcome was time to decrease intramuscular
temperature 8°C below baseline. A secondary
outcome was intramuscular temperature at the
end of a 90-minute rewarming period. Paired t
tests were used to examine outcomes.
TTRESULTS: Time to reach an 8°C reduction in
intramuscular temperature was not significantly
different between CIB and CWI (mean difference,
2.6 minutes; 95% confidence interval: –3.10, 8.30).
Intramuscular temperature remained significantly
colder 90 minutes post-CWI compared to CIB
(mean difference, 2.8°C; 95% confidence interval:
2.07°C, 3.52°C).
TTCONCLUSION: There was no difference in time
required to reduce intramuscular temperature
8°C 1 cm below adipose tissue using CIB and CWI.
However, intramuscular temperature remained
significantly colder 90 minutes following CWI.
These results provide clinicians with information
that may guide treatment-modality decisions.
J Orthop Sports Phys Ther 2012;42(8):731-737,
Epub 23 March 2012. doi:10.2519/jospt.2012.4200
TTKEY WORDS: adipose tissue, cold-water immersion, ice bag
Cryotherapy can be applied in various
forms, but crushed-ice bags (CIB) and
cold-water immersion (CWI) are frequently used in sports medicine. These 2
modalities have different levels of efficacy
in inducing physiologic changes. When
compared to CIB, CWI has been shown
to be more effective in reducing nerve
conduction parameters after a 15-minute cooling treatment8 and maintaining
the reductions in sensory nerve conduction parameters during rewarming.7 In a
study by Myrer et al,17 both CIB and CWI
decreased intramuscular temperature after a 20-minute treatment, and there was
no difference in immediate posttreatment
temperature between the modalities. But
in the same study, during the 30-minute
posttreatment monitoring period, intramuscular temperature increased 2°C
after the ice bag was removed, whereas
intramuscular temperature continued
to decrease nearly 2°C after CWI was
removed.17
In clinical practice, the same cryotherapy modalities can be applied in
multiple ways. Ice bags can be applied with flexible plastic wrap, elastic
wrap, or without compression. CWI
can be applied at various depths and
temperatures, with typical immersion
Doctoral candidate, Curry School of Education, University of Virginia, Charlottesville, VA. 2Resident, Physical Medicine and Rehabilitation, University of Virginia, Charlottesville,
VA. 3Professor, Curry School of Education, University of Virginia, Charlottesville, VA. 4Assistant Professor, Curry School of Education, University of Virginia, Charlottesville, VA.
There was no internal or external funding for this study. The authors affirm that they have no personal or financial affiliation (including research funding) or involvement with any
commercial organization that has a direct financial interest in any matter included in this manuscript. The University of Virginia Institutional Review Board approved this study.
Address correspondence to Kimberly Rupp, 210 Emmet Street, Box 400407, Charlottesville, VA 22904. E-mail: [email protected] t Copyright ©2012 Journal of Orthopaedic
& Sports Physical Therapy
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[
just proximal to the injured area, and
at temperatures ranging from 10°C to
15°C. Previous authors have made treatment time recommendations based on
subcutaneous adipose tissue thickness.
Their studies reported that cooling time
was affected by thickness of adipose tissue at the treatment site, and that longer
treatments were necessary for greater
thicknesses.14,18,19 Treatment time is another consideration. Intramuscular temperature 1 to 2 cm below adipose tissue
has been reported to decrease 7°C to
8°C using CIB14,15,19 but only 5°C17 using
CWI, after conventional treatment times
of 20 to 30 minutes. Additionally, a recent study examining blood flow during
cryotherapy treatments22 concluded that
the previously recommended treatment
times19 to achieve a 7°C change in intramuscular temperature may not be sufficient to reduce blood flow and achieve
desired physiological effects.
Although clinicians and researchers
often assume that it is better to have a
lower temperature for a longer duration
after treatment,7,15 a consensus on optimal treatment parameters has not been
reached. The purpose of this study was
to compare the length of time required
to decrease intramuscular temperature
8°C below baseline temperature after
treatment with CIB and CWI. Secondary aims were to examine intramuscular
temperature between the modalities 90
minutes postintervention, the relationship between cooling time and adipose
tissue thickness, and the perceived thermal discomfort during each cryotherapy
modality. Based on the study by Myrer
et al,17 we hypothesized that CIB and
CWI would result in similar rates of intramuscular temperature decrease, and
that CWI would result in a colder intramuscular temperature after a rewarming
period. We also hypothesized that the
time required to decrease intramuscular
temperature 8°C would be positively correlated with adipose thickness, and that
during treatment CIB would result in
less perceived thermal discomfort than
CWI.
research report
METHODS
Design
W
e used a crossover study design, in which each subject underwent separate randomly allocated
treatments of CIB or CWI, with at least
72 hours between treatment sessions.
Participants
Eighteen healthy subjects, 7 men (mean
 SD age, 22.9  2.0 years; height, 180.3
 8.2 cm; mass, 84.9  17.9 kg; medial
calf adipose thickness, 1.4  0.58 cm;
calf girth, 39.6  4.5 cm) and 11 women (mean  SD age, 21.8  1.3 years;
height, 163.0  4.9 cm; mass, 57.3  5.7
kg; medial calf adipose thickness, 1.8 
0.39 cm; calf girth, 34.3  1.6 cm), were
recruited from a university setting and
volunteered to participate in this study.
No participant had a history of allergy to
lidocaine or cold (including cold hypersensitivity or Raynaud syndrome), known
circulatory compromise in the lower extremity, or open wound on the lower leg
of the test extremity at the time of testing.
All participants were instructed in study
procedures and gave written, informed
consent. The Institutional Review Board
at the University of Virginia approved
this study.
Procedures
Prior to the treatment sessions, subjects completed a screening session to
determine the thickness of subcutaneous adipose tissue on the medial calf.
Initially, calf girth was measured and
marked at the largest circumference of
the nondominant calf, determined as
the limb opposite the limb preferred to
kick a ball. This mark at the medial calf
served as the measurement site for subcutaneous adipose tissue, as well as the
thermocouple insertion site. Ultrasound
images (LOGIQ Book XP; GE Healthcare, Waukesha, WI) were recorded at
the same site in B-mode, using an 8-MHz
linear-array transducer to capture a still
image. Images were measured using ImageJ Version 1.43u software (National
]
Institutes of Health, Bethesda, MD) at
a resolution of 46 pixels per centimeter
for each image. Adipose tissue thickness
was determined as the depth from the cutaneous boundary to the inferior aspect
of the fascia surrounding the gastrocnemius.4 The mean thickness of 3 images
was recorded and used to determine the
thermocouple insertion depth for each
subject. Ultrasound imaging is comparable to magnetic resonance imaging,
the criterion standard, in image clarity25
and is a valid tool for measuring both abdominal and visceral adipose tissue.4 We
have found this measurement technique
to be highly reliable in our laboratory.
We measured intramuscular temperature using an 18-gauge, type T (copper-constantan thermocouple), special
flexible microprobe (IT-18; Physitemp
Instruments, Inc, Clifton, NJ), interfaced with a Thermes USB temperature
data-acquisition system (Physitemp
Instruments, Inc), with a manufacturer-reported accuracy of 0.2°C. Intramuscular temperature was measured
at 1 Hz to the nearest 10th of a degree
throughout the study, using the same
thermocouple, a procedure that we have
found to be reliable in our laboratory.
For each subject, the thermocouple was
marked at 1 cm plus adipose tissue thickness, as determined by ultrasound imaging. The thermocouple was sterilized
using CIDEXPLUS 28-Day Solution
(Johnson & Johnson, Irvine, CA), per
manufacturer guidelines.
Subjects were positioned prone on a
treatment table, and the area of largest
girth was marked on the medial calf, using a 2.5 × 2.5-cm right-angle template
to delineate the thermocouple insertion
area. A disposable underpad was placed
under the lower limb of the test leg. The
insertion area was shaved, if needed, and
cleansed with a 10% povidone-iodine
solution. A physician anesthetized the
surface area with an injection of 3 cc of
1% lidocaine hydrochloride (10 mg/mL)
(Hospira, Inc, Lake Forest, IL), using a
21-gauge hypodermic needle. The same
physician then inserted the marked ther-
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TABLE
Baseline intramuscular
Descriptive Values and BetweenGroup Differences for Primary and
Secondary Outcome Measures
Crushed-Ice Bag*
Cold-Water Immersion*
Between-Group Difference†
38.59  1.26
38.64  0.92
–0.05 (–0.41, 0.31)
42.51  20.4
39.91  14.5
2.60 (–3.10, 8.30)
33.49  2.26
30.69  2.17‡
2.80 (2.08, 3.52)
3.92  2.25
5.24  2.61
–2.15 (–2.14, –0.49)
temperature, °C
Time to decrease intramuscular
temperature 8°C, min
90-min postintervention
temperature, °C
Thermal discomfort, cm
*Values are mean  SD.
†
Values are mean (95% confidence interval).
‡
Indicates that the postintervention intramuscular temperature was significantly lower following
cold-water immersion compared to crushed-ice bag (P<.001).
mocouple into the medial calf using an
18-gauge hypodermic needle, and verified correct insertion depth through visual examination after withdrawal of the
hypodermic needle. At the appropriate
insertion depth, the ink marking was visible and level with the skin. A transparent
sterile film dressing (Tegaderm; 3M, St
Paul, MN) was then placed over the insertion site.
After a 5-minute baseline temperature recording, each subject received a
randomly allocated treatment condition
of CIB or CWI. Each ice bag was made
by placing 1500 mL of crushed ice into a
38 × 51-cm plastic bag and evacuating the
bag of excess air before closing it. Ice bags
were secured with consistent compression, using an elastic wrap. The bladder
of a manometer was placed over the ice
bag and under the elastic wrap. Pressure
was adjusted and monitored to maintain
a reading of 40 to 50 mmHg throughout
each ice-bag session. Cold-water immersion was completed in a 10-gallon
(37.85-L) tub, filled with crushed ice and
cold water to maintain a temperature
of 12°C and stirred frequently. Subjects
wore a toe cover (PRO Orthopedic Devices, Inc, Tucson, AZ) for the duration
of CWI. Each subject immersed his or her
lower leg to just below the knee and was
instructed to avoid unnecessary ankle
dorsiflexion and plantar flexion to mini-
mize thermocouple movement or migration. Each cryotherapy treatment (CIB
or CWI) was applied until intramuscular
temperature decreased 8°C from baseline. At this point, the intervention was
removed and, if necessary, the subject’s
lower leg was lightly patted dry and the
toecap removed. Immediately posttreatment, subjects were asked to rate perceived thermal discomfort at the most
intense point of treatment using a 10-cm
visual analog scale, with a left anchor of
“very comfortable” and a right anchor of
“very uncomfortable.” Rewarming of the
muscle was monitored for 90 minutes
posttreatment, while the participant
lay prone. After the rewarming period,
the thermocouple was removed and replaced in CIDEXPLUS 28-Day Solution,
and the insertion site was cleansed with a
70% isopropyl alcohol swab and covered
with a bandage. The subject was then dismissed and asked to return 3 to 7 days
later to complete the other randomly allocated treatment.
Statistical Analysis
Data were analyzed using SPSS Version
17.0 (SPSS Inc, Chicago, IL). Data were
normally distributed, so paired t tests
were used to examine (1) baseline intramuscular temperature before each intervention, (2) length of time to decrease
8°C during intervention, (3) intramus-
cular temperature after rewarming, and
(4) thermal comfort at the most intense
sensation during cryotherapy treatment.
A Kaplan-Meier survival analysis was
also performed to assess the length of
time necessary to decrease 8°C between
interventions. Survival was defined as a
subject not yet reaching the 8°C decrease.
Pearson r correlations were used to examine the relationship between CIB and
adipose thickness, and CWI and adipose
thickness. The level of significance was
set at P<.05 for all analyses.
RESULTS
B
aseline intramuscular temperature was not significantly different
before the start of each intervention
(mean difference, –0.05°C; 95% confidence interval [CI]: –0.41°C, 0.31°C)
(TABLE). Adipose tissue thickness was
greater in females than males (mean difference, 0.42 cm; 95% CI: 0.19, 0.64).
The amount of time needed to cause
a decrease of 8°C in intramuscular temperature was not significantly different
between interventions (mean difference,
2.60 minutes; 95% CI: –3.10, 8.30)
(TABLE). Likewise, the survival analysis
showed no significant difference in the
length of time necessary to decrease intramuscular temperature by 8°C between
interventions (FIGURE 1). Intramuscular
temperature was significantly colder 90
minutes postintervention after CWI compared to CIB (mean difference, 2.80°C;
95% CI: 2.08°C, 3.52°C) (TABLE, FIGURE
2). Compared to baseline temperature,
intramuscular temperature 90 minutes
postintervention remained lower in both
conditions (CWI mean difference, 7.95°C;
95% CI: 7.23°C, 8.66°C; CIB mean difference, 5.10°C; 95% CI: 4.29°C, 5.91°C).
There was no correlation between
time required to decrease intramuscular temperature 8°C and adipose tissue
thickness in CWI (r = 0.04, P = .874)
(FIGURE 3) and CIB (r = –0.25, P = .320)
(FIGURE 4). Perceived ratings of thermal
discomfort were not significantly different between interventions (mean differ-
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Percentage of Subjects Who Did Not Reach 8°C Decrease
100
90
80
70
60
50
40
30
20
10
0
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
Time, min
FIGURE 1. Survival analysis for the percentage of subjects who did not reach 8°C intramuscular temperature
decrease at each 1-minute time interval during cold-water immersion and crushed-ice bag. No significant
differences were found between interventions (P = .59). The blue line represents cold-water immersion and the
orange line represents crushed-ice bag.
ence, –1.32 cm; 95% CI: –2.15, –0.49)
(TABLE).
DISCUSSION
T
he main finding of this study
was that the time required to decrease intramuscular temperature
by 8°C was not significantly different
between the different cryotherapy interventions. However, after 90 minutes of
rewarming while lying prone, intramuscular temperature was significantly colder after treatment with CWI compared to
CIB. Additionally, there were no correlations between time needed to decrease
intramuscular temperature 8°C and adipose tissue thickness or significant difference in perceived thermal discomfort
between the 2 different interventions.
Previous research has reported that
intramuscular temperatures decrease
from 7°C after a 20-minute treatment17
to 8°C after a 30-minute treatment14
with ice bags, and 5°C after a 20-minute
treatment with CWI. Although the optimal magnitude of temperature change
with cryotherapy is unknown, we chose
an 8°C change as the target temperature,
because most therapeutic treatments
are similar in time and methodology to
those in the range of 7°C to 8°C temperature change. We monitored temperature
change in a mechanism similar to clinical cryotherapy applications to compare
both time to cooling and temperature after a lengthy rewarming period.
To our knowledge, this is the first
study to use a survival analysis to examine the time required to reduce intramuscular temperature to a specific threshold
(FIGURE 1). The survival analysis represented the percentage of subjects who did
not reach the 8°C temperature-reduction
threshold at each 1-minute time interval.
As each subject reached the 8°C threshold, the subject was removed from the
remaining intervals of the analysis, until
the last subject reached the threshold, at
which point the analysis was complete.
Such a survival analysis enables clinicians
to examine the time required to decrease
intramuscular temperature. As shown in
FIGURE 1, the majority of subjects required
more than 30 minutes of cryotherapy application to decrease intramuscular temperature, which brings into question the
ability of general clinical practice tech-
]
niques to adequately cool the muscle.
We hypothesized that required cooling
time and adipose tissue thickness would
be positively correlated. Our results
found no correlation between cooling
time and adipose tissue thickness with
either intervention (FIGURES 3 and 4). This
may be due to the body composition of
our subjects, of whom the majority had
adipose tissue thicknesses between 11 and
20 mm and only a few had extremely thin
or thick levels of adipose tissue. Otte et
al19 concluded that a standard 20-minute treatment was inadequate to produce
standard intramuscular temperatures in
patients with different body compositions
and made treatment-time recommendations based on subcutaneous adipose tissue thickness over the treatment area.
These treatment times, to achieve a 7°C
decrease in intramuscular temperature,
were 12 minutes for patients with 0- to
10-mm adipose tissue, 30 minutes for
patients with 11- to 20-mm adipose tissue, 40 minutes for patients with 21- to
30-mm adipose tissue, and 60 minutes
for patients with 31- to 40-mm adipose
tissue. Recently, Selkow et al22 examined
microvascular blood flow with ice-bag
treatments using these treatment-time
recommendations, and reported that intramuscular blood flow did not decrease
below baseline levels immediately after
ice-bag treatment, despite an intramuscular temperature decrease of 7°C.
In our study, previous treatment-time
recommendations would not have resulted in the desired decreases in intramuscular temperature 1 cm below adipose
tissue. The majority of our subjects had
adipose tissue thicknesses of 11 to 20
mm, as measured with real-time ultrasound imaging. To achieve the desired
decrease in intramuscular temperature,
these subjects would have required a
30-minute treatment, based on the above
recommendations. Our results, using
real-time ultrasound, indicated a treatment time of closer to 40 minutes for this
subgroup, regardless of the cryotherapy
method used. The treatment-time difference in the present study may be due
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35
34
Temperature, °C
33
32
31
30
29
28
27
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
Time, min
FIGURE 2. Means and 95% confidence intervals during rewarming. The blue lines represent cold-water immersion
and the orange lines represent crushed-ice bag, with solid lines as the mean and dotted lines as the 95%
confidence interval. Areas where confidence intervals do not overlap (73 through 90 minutes) indicate significant
difference (mean difference, 2.8°C  0.72°C; P = .001).
30
25
Adipose Thickness, mm
to a target intramuscular temperature
change that was slightly greater than that
of the previous study. It is also possible
that intramuscular tissue temperatures
were measured at a more accurate tissue
depth than those of the previous study,
which used skinfold calipers to measure
skin and adipose tissue and to determine
thermocouple placement. We believe that
using real-time ultrasound imaging is superior as a research method compared to
skinfold calipers, because this method
enabled us to visualize the fascial lines
separating adipose tissue from the gastrocnemius and to objectively measure
the thickness of adipose tissue.23
Although both groups remained
cooler than they were at baseline, intramuscular temperature was significantly
colder after a 90-minute rewarming period following CWI compared to CIB.
These results are similar to those of previous studies measuring intramuscular
temperature 30 minutes posttreatment17
and sensory nerve conduction velocity 30
minutes posttreatment.7 In each of those
studies, CWI cryotherapy was more effective at creating longer-lasting effects
and may therefore be a more effective
treatment. Both CIB and CWI remove
heat from treated tissues via conduction,
which involves direct contact of the intervention with the treatment area. It may
be that CWI is more effective at creating
longer-lasting effects due to the ability of
moving water to remove additional heat
from treated tissues through convection.
Merrick et al15 explained that the addition
of a second mode of heat transfer, in our
case convection, might produce different
treatment effects from those from conduction alone. In our study, CIB and CWI
intramuscular temperatures were similar
from the end of the treatment period to
73 minutes, but differed significantly during the final 17 minutes of rewarming.
After 90 minutes, subjects treated with
CWI had a 2.8°C  0.72°C lower intramuscular temperature than those treated
with CIB. This significant difference is
depicted in FIGURE 2 where the 95% CIs
do not overlap, showing a difference in
20
15
10
5
0
0
10
20
30
40
50
60
70
80
90
100
Time, min
FIGURE 3. Cold-water immersion correlation analysis. Time to reach 8°C decrease in intramuscular temperature
(minutes) and adipose tissue thickness over the medial gastrocnemius (millimeters). No significant correlation was
found between cooling time with cold-water immersion and adipose tissue thickness (r = 0.04, P = .874).
muscle temperature during rewarming.
In our study, the rewarming period was
completed with the subject lying prone
for 90 minutes. Recently, a study exam-
ined muscle temperature changes during
exercise combined with cryotherapy and
reported that optimal muscle temperature occurs at rest.6 The authors of that
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study was recruited from a university
setting and consisted of healthy young
adults who did not have a history of lower
extremity injury in the 6 weeks prior to
enrollment. Due to this limitation, the
study results could not be generalized to
an injured population and only provide
information regarding uninjured adults.
Additionally, our sample size of 18 subjects in a crossover design may be considered relatively small.
30
25
Adipose Thickness, mm
]
20
15
10
CONCLUSION
5
0
0
10
20
30
40
50
60
70
80
90
100
Time, min
FIGURE 4. Crushed-ice bag correlation analysis. Time to reach 8°C decrease in intramuscular temperature
(minutes) and adipose tissue thickness over the medial gastrocnemius (millimeters). No significant correlation was
found between cooling time with crushed-ice bag and adipose tissue thickness (r = –0.25, P = .320).
study recommended that patients walk
the shortest amount of time possible and
increase the length of cryotherapy treatment once they stop walking.6
Subject ratings of perceived comfort
during each treatment were not significantly different between CIB and CWI,
but the P value and moderate effect size
of this measure indicate that CWI might
have caused greater discomfort than CIB.
This is supported by anecdotal reports
from patients who find CWI more uncomfortable than CIB. In this instance,
unless the treatment goals are specifically aimed at a longer-lasting decrease
in muscle temperature to achieve physiologic changes, as opposed to achieving
cold-induced analgesia, using CIB is an
acceptable alternative to CWI to minimize patient discomfort.
Regarding our tissue temperaturechange parameters, we chose a threshold
of an 8°C decrease from baseline, which
is representative of the best available
current information.14,17,22 Similarly, our
intervention parameters were chosen
based on common previously reported
parameters.10,17 Water temperature during immersion was monitored and kept
consistently at 12°C, but ice-bag temperature was not monitored throughout treatment. Though we are confident that the
ice-bag temperature remained constant,
due to cryotherapy thermodynamics and
the concept of phase change (ice changing from solid form to liquid form), the
concept of fusion, or melting, is important to consider.15 The melting point of
ice is 0°C. Fusion occurs without a temperature change, so that solid ice immediately before melting and liquid water
immediately after melting are both 0°C.15
As long as there was still solid ice in the
ice bag at the end of treatment (because
there wasn’t enough heat absorbed by
the ice to cause melting), we know that
the temperature of the intervention remained constant at 0°C.
We are unable to generalize these
results to all cryotherapy interventions,
because the magnitude and duration of
cooling are likely different when using
different parameters. Also, it is important
to consider that cryotherapy applied over
a joint or superficial bony prominence
may produce different physiological effects with respect to the extent and rate
of cooling.9,20,21 The population in this
T
his study provides additional
insight on applications of cryotherapy. Though we chose specific and
justified modality application parameters, many clinicians and researchers may
choose different parameters. The lack
of standard and proven parameters to
achieve a clinical goal may be part of the
reason that research on the clinical benefits of cryotherapy is inconsistent and inconclusive.2,11 Future research should aim
to determine a specific target tissue temperature that helps optimize healing after
injury. A comparison of different applications of the same modality may also be
useful, in that the ability to recommend
standard treatment protocols based on
body composition and injury type may
enable patients to recover faster and experience less discomfort during recovery.
Currently, treatment decisions should be
directed by treatment goals. Both CIB
and CWI cool muscle tissue in similar
time durations, but CWI leaves tissue
cooler longer after a rewarming period.
This study supports consideration of the
posttreatment activity of each patient. To
maximize cooler temperatures after cryotherapy, subjects may need longer treatment times, combined with a period of
passive rest, before continuing activities
of daily living. t
KEY POINTS
FINDINGS: The time required to reduce
intramuscular temperature 8°C was
not significantly different between CIB
and CWI, although average times were
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longer than those typically used clinically. After 90 minutes of rewarming,
intramuscular temperature was significantly colder after treatment with CWI
compared to CIB.
IMPLICATIONS: CWI and CIB both cool
muscle tissue in similar time durations,
but CWI leaves tissue cooler longer after
a rewarming period. To maximize cooler
temperatures after cryotherapy, subjects
may need longer treatment times combined with a period of passive rest before continuing activities of daily living.
CAUTION: We do not currently know if
there is a specific target tissue temperature that would optimize healing after
injury. It is possible that important
physiological changes occur in the skin
or muscle before or after an 8°C intramuscular temperature decrease.
ACKNOWLEDGEMENTS: We would like to thank
Brittany Swann for her assistance with data
collection, as well as Dr Matthew Milewski, Dr
John Minnich, and Dr Jeff Tuman for their
assistance with thermocouple insertion.
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journal of orthopaedic & sports physical therapy | volume 42 | number 8 | august 2012 | 737
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