Athletic Training and Sports Health Care

Original Research 

Influence of Topical Analgesic Cream on Passive Hip Flexion Range of Motion, Sensation of Pressure, and Temperature

Blaine C. Long, PhD, AT, ATC; Kevin C. Miller, PhD, AT, ATC

Abstract

Health care professionals often apply analgesic creams to their patients to minimize pain. However, these creams are claimed to have other physiological effects in addition to pain relief. There is currently conflicting evidence on their benefits. The authors' objective was to determine if an analgesic cream influences skin temperature, sensation of pressure, and hip flexion range of motion (ROM) in patients possessing less than 90° of hip ROM immediately and at 15 minutes following application. Individuals received one of the four treatments (FLEXALL 454 Maximum Strength Cream [Ari-Med Pharmaceuticals, Tempe, AZ] and stretching, placebo cream and stretching, no cream and stretching, and control [nothing]) according to a balanced Latin square. Passive hip flexion ROM increased from baseline regardless of treatment (F2,32 = 31.50; P < .001). The analgesic cream decreased skin temperature immediately and at 15 minutes following application (P < .05). Application of the placebo cream and stretching also decreased skin surface temperature after application, but temperature returned to baseline 15 minutes following application (P < .05). Skin temperature did not change within the no cream and stretching or control groups immediately or at 15 minutes after application (P > .05). Sensation of pressure decreased immediately and at 15 minutes following application with the analgesic cream (P < .05) but did not change for the other treatments (P > .05). When analgesic creams are applied to the hamstring muscle group, it appears that they produce a small decrease in skin surface temperature and sensation of pressure for up to 15 minutes following application but do not influence passive hip flexion ROM. [Athletic Training & Sports Health Care. 2016;8(2):55–62.]

Abstract

Health care professionals often apply analgesic creams to their patients to minimize pain. However, these creams are claimed to have other physiological effects in addition to pain relief. There is currently conflicting evidence on their benefits. The authors' objective was to determine if an analgesic cream influences skin temperature, sensation of pressure, and hip flexion range of motion (ROM) in patients possessing less than 90° of hip ROM immediately and at 15 minutes following application. Individuals received one of the four treatments (FLEXALL 454 Maximum Strength Cream [Ari-Med Pharmaceuticals, Tempe, AZ] and stretching, placebo cream and stretching, no cream and stretching, and control [nothing]) according to a balanced Latin square. Passive hip flexion ROM increased from baseline regardless of treatment (F2,32 = 31.50; P < .001). The analgesic cream decreased skin temperature immediately and at 15 minutes following application (P < .05). Application of the placebo cream and stretching also decreased skin surface temperature after application, but temperature returned to baseline 15 minutes following application (P < .05). Skin temperature did not change within the no cream and stretching or control groups immediately or at 15 minutes after application (P > .05). Sensation of pressure decreased immediately and at 15 minutes following application with the analgesic cream (P < .05) but did not change for the other treatments (P > .05). When analgesic creams are applied to the hamstring muscle group, it appears that they produce a small decrease in skin surface temperature and sensation of pressure for up to 15 minutes following application but do not influence passive hip flexion ROM. [Athletic Training & Sports Health Care. 2016;8(2):55–62.]

Analgesic creams are commonly applied to the skin for temporary relief of pain. In athletic venues, athletes or health care professionals apply these analgesic creams to an ailing muscle or joint prior to or after physical activity. When an analgesic cream containing the active ingredient menthol is applied to the skin, it is reported that the active ingredient has an influence on skin sensitivity,1–4 tissue temperature,5,6 pain,7–9 and blood flow conductance.10,11

Previous studies on the clinical use of analgesic creams containing menthol are limited. One study reported that an analgesic cream applied to the skin initially produced a cooling sensation followed by a warming sensation,5 giving the impression that it may change skin surface temperature12 and potentially influence range of motion (ROM) or sensation of pressure (ie, a technique commonly used to assess for numbness). However, the authors in this study reported that when applied to the hamstring muscle group, the analgesic cream did not alter passive hip flexion ROM, skin temperature, or sensation of pressure immediately following application.12

Although this information regarding analgesic creams has provided some insight into the understanding of its use, it is possible that assessing the effects of the analgesic cream occurred too soon following application. The lack of any observed changes may have been attributed to the time at which the measurements were taken.

It may be considered impractical to assess the efficacy of analgesic creams immediately following application in a clinical setting. Assessing their effects over time would allow analgesic creams to absorb into the tissue prior to observing any physiological changes. The purpose of this study was to determine whether an analgesic cream containing menthol influences skin surface temperature, sensation of pressure, and passive hip flexion ROM in patients possessing less than 90° of passive hip flexion ROM immediately and at 15 minutes following application.

Methods

Study Design

We used a double-blind 3 × 4 crossover design with repeated measure on all factors to guide data collection. The independent variables were time (baseline, immediately after application, and 15 minutes after application) and treatment (3 cc of a counterirritant cream [FLEXALL 454 Maximum Strength; (Ari-Med Pharmaceuticals, Tempe, AZ; 16% of menthol and stretching], 3 cc of placebo counterirritant cream [massage lotion with mint and peppermint oil] and stretching, no cream and stretching, and nothing [no cream and no stretching; control]) to the dominant leg (ie, leg with which patients kicked a ball). The dependent variables were skin surface temperature (°C), sensation of pressure (gram), and passive hip flexion ROM (°).

Patients

Twenty college-aged recreationally active patients (male = 10, age = 21.2 ± 0.63 years, height = 176.53 ± 8.99 cm, mass = 82.19 ± 16.36 kg; female = 10, age = 21.1 ± 0.74 years, height = 170.18 ± 12.62 cm, mass = 67.86 ± 14.28 kg) volunteered to participate in the study. Prior to participating, patients filled out a health history questionnaire to ensure they had no known lower extremity injuries in either leg in the 6 months prior to data collection, were not participating in a stretching program, did not have skin irritation or skin allergies, did not have loss of circulation, sensation, or muscle function in either leg, had no neurological condition that influenced hamstring flexibility, and were not taking over-the-counter or prescription pain medication.

Prior to data collection, patients were examined to ensure that they had less than 90° of passive hip flexion ROM in their dominant leg. To determine if they had less than 90°, the patients were positioned supine on a padded table. They were then passively stretched and instructed to inform the investigator when the passive stretch become uncomfortable. If this level of discomfort was less than 90° and the patient did not have any exclusion criteria, the individual was included in the study. Each patient then gave written informed consent to participate in this university-approved study before being randomly assigned to a treatment order established with a balanced Latin square.

Instruments

A Baseline Bubble Inclinometer (Tech-Med Services, Inc., Hauppauge, NY) was used to measure passive hip flexion ROM in the supine position. The bubble inclinometer was placed at the middle and center portion of the patients' tibia. The use of a bubble inclinometer is reported to have an intrarater reliability ranging from .92 to .97.13,14

To determine sensation of pressure, we used Semmes–Weinstein Monofilaments (North Coast Medical, Inc., San Jose, CA). Monofilaments are small plastic wires with varying diameters and weight (g). The intrarater reliability of these monofilaments is reported to range between 0.87 and 0.92.15

Two type-T copper-constantan surface thermocouples (Physitemp Instruments, Inc., Clifton, NJ) were connected to an Iso-Thermex electrothermometer (Columbus Instruments, Columbus, OH) to measure skin and ambient temperature. To secure the surface thermocouple to the skin, we used Transpore Surgical tape (3M, St. Paul, MN). To ensure temperature and sensation of pressure were measured at the same location across the 4 days of data collection, we marked the midpoint between the popliteal fossa and gluteal fold with a surgical marker. We used separate 5-cc BD syringes (Becton Dickinson & Co., Franklin Lakes, NJ) to extract 3 cc of FLEXALL 454 Maximum Strength cream from one container and an equal amount of Mueller Unscented Massage Lotion (Mueller Sports Medicine, Inc., Prairie du Sac, WI) combined with 2 mL of pure peppermint and 2 mL of pure mint extract (J.R. Watkins, Winona, MN) as a placebo from another container. The 3 cc amount was established based on a previous published study.12

To verify that we used 3 cc, the FLEXALL and placebo creams were stored in separate 16-oz containers labeled “A” and “B.” One investigator not involved with data collection was responsible for extracting the correct amount for each patient.

Procedures

Patients reported to the laboratory dressed in shorts and a t-shirt. Upon arrival, each patient completed the health history questionnaire and was then randomly assigned to a treatment group. The treatment group was established by pulling a piece of paper from a bowl. Based on the order of numbers indicated on the paper, patients received: (1) 3 cc of a counterirritant cream (FLEXALL 454 Maximum Strength) and static stretching, (2) 3 cc of a placebo counterirritant cream (lotion with mint and peppermint oil extract) and static stretching, (3) no cream and static stretching, or (4) nothing on 4 days separated by 24 hours, with data collection occurring at approximately the same time each day.

Patients were then positioned supine on a padded table. While laying supine, the patient's non-dominant leg and hip were secured with belts to minimize accessory movements during the passive hip flexion ROM measures. One belt was applied over the thigh just superior to the non-dominant knee and the second belt was positioned over the anterior superior iliac spine (Figure 1). The bubble inclinometer was then placed on the middle of the dominant lower leg in line with the base of the patella and talocrual joint (Figure 2). Hip flexion ROM measures were then performed by passively flexing the patient's hip three consecutive times with a 30-second break between each measure.


Patient positioning for static stretching of the hamstring muscle group. To minimize accessory motions a belt was applied to the patients' waist and to their non-dominant leg.

Figure 1.

Patient positioning for static stretching of the hamstring muscle group. To minimize accessory motions a belt was applied to the patients' waist and to their non-dominant leg.


Method of assessing passive hip flexion range of motion in the supine position. Measurements were taken using a Baseline bubble inclinometer (Tech-Med Services, Inc., Hauppauge, NY).

Figure 2.

Method of assessing passive hip flexion range of motion in the supine position. Measurements were taken using a Baseline bubble inclinometer (Tech-Med Services, Inc., Hauppauge, NY).

We then assessed the patient's sensation of pressure. Each measure was taken by applying a monofilament directly to the skin at the center point between the gluteal fold and popliteal fossa until it bent and held for approximately 1.5 seconds (Figure 3). We first applied the middle level of monofilaments (4.56) at the center point. The investigator then selected the next lighter or heavier monofilament gauge based on whether or not the patient felt the monofilament. Once the patient did not feel the monofilament, we documented the previous monofilament number (gram) as the level of sensation.


Application of the Semmes–Weinstein Monofilaments (North Coast Medical, Inc., San Jose, CA) to the patients' hamstring muscle group. Measurements were taken three consecutive times.

Figure 3.

Application of the Semmes–Weinstein Monofilaments (North Coast Medical, Inc., San Jose, CA) to the patients' hamstring muscle group. Measurements were taken three consecutive times.

Within 30 seconds of the last sensation of pressure measure, we applied the surface thermocouple to the marked midpoint in the center of the hamstring muscle group. Skin surface temperatures were then recorded every minute for 5 minutes prior to each condition.

Patients then positioned themselves prone and received one of the four treatments to their hamstring muscle group. The FLEXALL 454 and placebo creams were applied from the gluteal fold to the superior portion of the popliteal fossa until they were completely absorbed, which is reported to take approximately 60 seconds.12 On the day patients were assigned to receive stretching with no cream applied and the day they received nothing, patients remained supine on the table where all measures were taken at the same time intervals.

Patients were then positioned supine, where the belts were reapplied to the non-dominant leg and over each anterior superior iliac spine. We then performed a series of three 30-second passive static hamstring stretches with a 30-second rest between each stretch. During each stretch, the investigator held the patient's leg in the hip flexion position to the point at which the patient subjectively reported discomfort. Immediately following the third stretch, passive hip flexion ROM, sensation of pressure, and surface temperature were measured again, all of which were performed by the same investigator.

Statistical Analysis

To compare treatments over time, an initial power analysis calculation was performed. With alpha = .05 and beta = .20 (power = .80), a minimum of 20 patients was required for sufficient power. We calculated means and standard deviation for passive hip flexion ROM, sensation of pressure, and skin surface temperature prior to, immediately following, and at 15 minutes following the application of FLEXALL 454 cream and stretching, a placebo cream and stretching, stretching and no cream, and nothing. To determine if there were differences between or within each treatment or time, separate two-way repeated measure analyses of variance were computed for each dependent variable. To identify differences, Tukey–Kramer post hoc multiple comparison tests and two-factor interaction tests were also computed.

Between-group effect sizes (Cohen's d) and 95% confidence intervals were also calculated. Number Crunchers Statistical Software 2007 version 07.1.9 (NCSS, LLC, Kaysville, UT) was used to analyze all data. The alpha level was set a priori at P < .05.

Results

Passive Hip Flexion Range of Motion

There was no difference between treatment for passive hip flexion ROM (F3,16 = 0.02; P = .99; 1 – β = 0.05). However, there was a significant main effect for time. Regardless of treatment, passive hip flexion ROM increased immediately and at 15 minutes after stretching (F2,32 = 31.50; P < .001; 1 – β = 1.0; Table 1).


Average Range of Motion (°), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD°) (n = 20)

Table 1.

Average Range of Motion (°), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD°) (n = 20)

Skin Surface Temperature

There was a significant two-factor interaction between condition and time (F6,32 = 11.91; P < .001; 1 – β = 0.41) for skin surface temperature. There was no difference in skin surface temperature between baseline temperatures between each condition (30.15°C ± 1.18°C, 30.55°C ± 1.17°C, 30.32°C ± 0.99°C, 30.34°C ± 1.08°C; Tukey–Kramer, P > .05). The application of FLEXALL 454 cream and stretching decreased skin surface temperature immediately and at 15 minutes following application (30.15°C ± 1.18°C, 29.35°C ± 1.01°C, 29.61°C ± 1.09°C, respectively; Tukey–Kramer, P < .05; Table 2). Skin surface temperature immediately and at 15 minutes after application for the FLEX-ALL 454 cream and stretching was also less than the no cream and stretching and control treatments, respectively (Tukey–Kramer, P < .05; Table 2). There was also a decrease in skin surface temperature for the placebo cream and stretching after application, but skin surface temperature returned to baseline at 15 minutes following application (30.55°C ± 1.17°C, 29.72°C ± 0.97°C, 30.27°C ± 0.68°C; Tukey–Kramer, P < .05). There was no difference in skin surface temperature across time for the no cream and stretching and control conditions (Tukey–Kramer, P < .05).


Average Skin Surface Temperature (°C), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD°C) (n = 20)

Table 2:

Average Skin Surface Temperature (°C), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD°C) (n = 20)

Sensation of Pressure

There was a significant interaction between condition and time (F6,32 = 3.37; P = .01 1 – β = 0.88) for sensation of pressure. Application of the FLEXALL 454 decreased sensation of pressure immediately and at 15 minutes following application (4.13 ± 0.12, 3.94 ± 0.27, 3.94 ± 0.29; Tukey–Kramer, P < .05; Table 3). Sensation of pressure did not change across time for the placebo and stretching, no cream and stretching, or for the control treatments (Tukey–Kramer, P > .05).


Average Sensation of Pressure (g), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD) (n = 20)

Table 3:

Average Sensation of Pressure (g), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD) (n = 20)

Discussion

The application of FLEXALL 454 cream and stretching to the hamstring muscle group did not influence passive hip flexion ROM immediately or at 15 minutes following application. This lack of change in passive hip flexion is similar to the results of Akehi and Long,12 who reported that FLEXALL 454 cream followed by stretching of the hamstring muscle group did not have an influence on passive hip flexion ROM immediately following application.

The use of FLEXALL 454 cream applied prior to stretching decreased skin surface temperature up to 15 minutes following application. In addition, the FLEXALL 454 cream also decreased sensation of pressure immediately after passive stretching. It has been suggested that topical creams containing menthol decrease6 or have no influence12 on skin surface temperature. In our study, the FLEXALL 454 and placebo creams decreased skin surface temperature immediately following application. Additionally, temperature with the FLEXALL 454 cream remained decreased at 15 minutes following application. This decrease in skin temperature appears to be the result of the active ingredient menthol in the FLEXALL 454 cream. This is also true with the placebo cream that contained mint oil extract and peppermint extract, both of which are primarily composed of menthol.16,17

It is reported that decreases in temperature following the use of products containing menthol is the result of sensory receptor activation, specifically the transient receptor potential (TRPM8) and the cold and menthol receptor 1 (CMR-1), both of which are part of the melastatin TRP subfamily, two receptors involved in thermosensitivity.6,18 Activation of both TRPM8 and CMR-1 receptors occurs when a cooling agent such as menthol is in contact with the skin or when products containing menthol are applied in rooms where ambient air temperature is less than 26°C.19 Ambient air temperature in our laboratory was approximately 19°C throughout data collection. In addition, temperature of the FLEXALL 454 cream and placebo creams when stored in our laboratory ranged between 20°C and 21°C, indicating that when applied to the skin they would have caused activation of the aforementioned receptors.

The observed decrease in skin surface temperature in our FLEXALL 454 cream and stretching and placebo cream and stretching groups immediately following application differs from the study by Akehi and Long.12 In their study, it was reported that the FLEXALL 454 and placebo creams combined with stretching did not influence skin surface temperature immediately following application. However, we observed a decrease in skin surface temperature immediately and at 15 minutes (∼0.5° to 0.8°C) following application.

Clinically, a decrease in skin surface temperature may help clinicians decide what therapeutic modality would be best when their goal is to alter the sensitivity to a stretch. Cooling tissue prior to stretching with a cold modality can significantly increase ROM.20–25 This increase in ROM is suggested to be caused by an observed decrease in nerve conduction velocity (hypoalgesic effects) within the involved muscles,20–25 whereas for every 1°C decrease in skin surface temperature there is a 0.4 m/s decrease in nerve conduction velocity.24 Based on these data, it appears that the magnitude of change in skin surface temperature following FLEXALL 454 application was not significant enough to have an impact on passive hip flexion ROM. As a result, even though skin surface temperature decreased with FLEXALL 454 cream, it should not be considered as an alternative method to other modalities when the goal is to increase passive hip flexion ROM.

Sensation of pressure is commonly used to quantify numbness.12,15,26,27 Clinically, numbness is often induced so that patients are free from pain and are able to perform their rehabilitative exercises. In this study, sensation of pressure decreased immediately following application with the FLEXALL 454 cream and stretching treatment and remained decreased at 15 minutes following application but did not change for the other groups. The changes in sensation of pressure are likely attributed to the effect menthol has on TRPM8 receptors. Once these voltage-gated channels are blocked, afferent input (eg, sensation of pressure) is minimized, ultimately lowering an individual's ability to perceive sensatory information.2 However, it should be noted that the clinical implications for this observed difference are likely insignificant. Sensation of pressure is measured in grams; thus, our observed difference from baseline was less than 0.2 g with a very small effect size (Table 3). In addition, immediately and at 15 minutes after application, sensation of pressure for the FLEXALL 454 cream and stretching was not different than any of the other treatments. It therefore appears that the concentration of menthol has an effect on the sensation of pressure.

A limitation to this study is the combined use of peppermint oil and mint oil as our placebo cream. Use of the peppermint oil extract and mint oil extract with massage lotion as our placebo cream was based on the assumption that patients may easily detect the difference between creams applied, given that analgesic creams containing menthol have a strong odor compared to massage lotion. When assessing analgesic creams, it is not uncommon for investigators to use an additive, as demonstrated by other investigators.12,28 However, in these investigations the authors only used mint oil, not the combination of mint oil and peppermint oil. It appears the combination of these two oils is responsible for the observed decrease in temperature.

Implications for Clinical Practice

The application of FLEXALL 454 cream provides an immediate decrease in skin surface temperature that lasts up to 15 minutes following application. In addition, it also produces a small decrease in sensation of pressure (ie, numbness) for up to 15 minutes following application. However, it does not appear that the observed decrease in skin surface temperature or sensation of pressure is significant enough to influence passive hip flexion ROM. These results, which differ from other reports, appear to be attributed to the active ingredient menthol and the ambient temperature in which the cream is used.

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Average Range of Motion (°), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD°) (n = 20)

PARAMETERBASELINEAPOST APPLICATIONA15 MIN POST APPLICATIONA
FLEXALL 454 and stretch73.05 ± 12.3277.54 ± 11.5676.30 ± 11.45
  Confidence interval(67.65, 78.45)(72.47, 82.61)(71.28, 81.32)
  Between-group effect size0.010.260.18
Placebo cream and stretch73.31 ± 8.4879.32 ± 9.1977.64 ± 10.51
  Confidence interval(69.59, 77.03)(75.29, 83.35)(73.03, 82.25)
  Between-group effect size0.040.470.32
No cream and stretch73.08 ± 8.8178.17 ± 10.4375.65 ± 9.02
  Confidence interval(69.22, 76.94)(73.6, 82.74)(71.7, 79.6)
  Between-group effect size0.010.330.14
Nothing72.93 ± 10.0974.61 ± 10.5874.26 ± 9.99
  Confidence interval(68.51, 77.35)(69.97, 79.25)(69.88, 78.64)

Average Skin Surface Temperature (°C), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD°C) (n = 20)

PARAMETERBASELINEPOST APPLICATION15 MIN POST APPLICATION
FLEXALL 454 and stretcha30.15 ± 1.1829.35 ± 1.01b29.61 ± 1.09b
  Confidence interval(29.63, 30.67)(28.91, 29.79)(29.13, 30.09)
  Between-group effect size0.170.630.52
Placebo cream and stretchc30.55 ± 1.1729.72 ± 0.9730.27 ± 0.68
  Confidence interval(30.04, 31.06)(29.29, 30.15)(29.97, 30.57)
  Between-group effect size0.180.280.12
No cream and stretch30.32 ± 0.9930.37 ± 1.02b30.15 ± 1.14b
  Confidence interval(29.89, 30.75)(29.92, 30.82)(29.65, 30.65)
  Between-group effect size0.020.340.009
Nothing30.34 ± 1.0830.01 ± 1.07b30.16 ± 1.02b
  Confidence interval(29.87, 30.81)(29.54, 30.48)(29.71, 30.61)

Average Sensation of Pressure (g), 95% Confidence Intervals, and Calculated Effect Size for Each Condition Across Time (Mean ± SD) (n = 20)

PARAMETERBASELINEPOST APPLICATION15 MIN POST APPLICATION
FLEXALL 454 and stretch4.13 ± 0.12a3.94 ± 0.29a3.94 ± 0.27a
  Confidence interval(4.08, 4.18)(3.81, 4.07)(3.82, 4.06)
  Between-group effect size0.500.360.09
Placebo cream and stretch4.05 ± 0.294.11 ± 0.214.03 ± 0.25
  Confidence interval(3.92, 4.18)(4.02, 4.2)(3.92, 4.14)
  Between-group effect size0.150.300.20
No cream and stretch4.14 ± 0.134.14 ± 0.154.12 ± 0.15
  Confidence interval(4.08, 4.2)(4.07, 4.21)(4.05, 4.19)
  Between-group effect size0.540.480.58
Nothing4.00 ± 0.344.04 ± 0.253.97 ± 0.33
  Confidence interval(3.85, 4.15)(3.93, 4.15)(3.83, 4.11)
Authors

From the School of Rehabilitation and Medical Sciences, Central Michigan University, Mount Pleasant, Michigan.

The authors have no financial or proprietary interested in the materials presented herein.

Correspondence: Blaine C. Long, PhD, AT, ATC, Department of Athletic Training, Office 1203, Central Michigan University, Mount Pleasant, MI 48859. E-mail: long4b@cmich.edu

Received: November 04, 2014
Accepted: November 23, 2015

10.3928/19425864-20160204-02

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