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Citation: Chen, D.; Yin, S.; Lu, X.; Fu,
H.; Gao, H.; Zhang, S. Research on the
Correlation Between Skin Elasticity
Evaluation Parameters and Age.
Cosmetics 2024,11, 205. https://
doi.org/10.3390/cosmetics11060205
Academic Editor: Maxim E. Darvin
Received: 2 October 2024
Revised: 8 November 2024
Accepted: 10 November 2024
Published: 26 November 2024
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4.0/).
Article
Research on the Correlation Between Skin Elasticity Evaluation
Parameters and Age
Dandan Chen 1,2, Shipeng Yin 2, Xuelian Lu 2, Haokun Fu 2, Hongqi Gao 2and Suning Zhang 1,*
1School of Perfume and Aroma Technology, Shanghai Institute of Technology, Fengxian, Shanghai 201418,
China; chendandan01@lqxgroup.com
2Shanghai Forest Cabin Biological-Tech Co., Ltd., Songjiang, Shanghai 201612, China;
dolen1900@163.com (S.Y.); luxuelian@lqxgroup.com (X.L.); kunmancy@outlook.com (H.F.);
gaohongqi@lqxgroup.com (H.G.)
*Correspondence: zsn@sit.edu.cn
Abstract: This study aims to explore the impact of aging on skin elasticity, a key biomechanical
property that diminishes over time, using the Cutometer to assess viscoelastic parameters. Methods:
Researchers analyzed 22 viscoelastic parameters from the facial skin of 60 women aged 18 to 70.
Key Results: The findings indicate that relaxation phase parameters, particularly biological elasticity
(R7), exhibited the strongest negative correlation with age (r =
−
0.62), signifying a notable decline
in biological elasticity as women age. In contrast, maximum deformation during the first cycle (R0)
and the total area under the upper curve after 10 cycles of deformation (F4) also showed significant
negative correlations with age (r =
−
0.47, r =
−
0.48), suggesting that younger skin typically presents
higher values. These correlations raise questions regarding practical applications, as the presence
of moisturizers and emollients may alter the stratum corneum’s properties, thus impacting these
measurements. Additionally, the ratio of delayed deformation to instantaneous deformation (R6)
demonstrated a positive correlation with age (r = 0.49), indicating its potential as a marker for
skin aging. Conclusions: This study highlights the critical role of relaxation phase parameters
in accurately reflecting skin elasticity changes associated with aging. The results offer valuable
insights for evaluating cosmetic efficacy, reinforcing the need for a nuanced understanding of how
various parameters interact. These findings contribute to the ongoing development of more effective
anti-aging treatments and products.
Keywords: skin elasticity; firmness; skin aging; age; Cutometer; correlation
1. Introduction
Being exposed to the environment, the skin, the body’s largest organ, undergoes
both intrinsic and extrinsic aging. Skin aging manifests as wrinkles, loss of elasticity,
sagging, and a rough appearance [
1
]. Intrinsic aging results from biological changes over
time, characterized by various histological, physiological, and biochemical modifications,
influenced by genetic factors (such as gender and ethnicity), differences in skin location,
and hormonal changes [
2
–
4
]. From a mechanical perspective, the skin functions as a layered
composite, exhibiting structural instability when subjected to stress, with the most apparent
manifestation being the formation of wrinkles [
5
–
8
]. As age increases, the gradual reduction
of elastic fibers significantly decreases the skin’s ability to bend, leading to a reduction in its
stability against wrinkling to a quarter of its original capacity [
9
]. This further emphasizes
the critical role of skin elasticity in the aging process. As global demographic shifts and
improvements in quality of life continue, anti-aging cosmetic technologies have become
a prominent focus in international beauty and medical research. Skin elasticity, as an
important biomechanical indicator for assessing skin health and youthfulness, has become
a core objective of many anti-aging treatments [8,10,11].
Cosmetics 2024,11, 205. https://doi.org/10.3390/cosmetics11060205 https://www.mdpi.com/journal/cosmetics
Cosmetics 2024,11, 205 2 of 13
Skin elasticity, firmness, and softness are critical biomechanical indicators for assessing
skin health and youthfulness [
8
]. The Cutometer, a non-invasive instrument for measuring
skin elasticity, operates by applying negative pressure to the skin and assessing its me-
chanical deformation. Using a non-contact optical measurement system, the Cutometer
accurately evaluates the skin’s ability to recover its shape after being subjected to me-
chanical stress [
12
–
14
]. It has multiple parameters, including Ue (elastic deformation), Uv
(viscous deformation), Uf (total deformation), Ur (elastic recovery), and Ua (viscous recov-
ery), along with R and Q parameters, which offer insights into the viscoelastic properties of
the skin [15–18].
As a globally recognized tool, the Cutometer has been widely adopted in dermatology,
cosmetic product development, efficacy evaluations, and studies of pathological skin
conditions. One of its major advantages is the standardized measurement it offers, allowing
for comparative studies across different populations and regions [
14
,
19
–
22
]. Additionally,
the Cutometer is user-friendly, provides rapid results, and has minimal requirements
regarding the skin condition of the subjects being tested [15,19].
Despite its extensive application in assessing skin elasticity and firmness, the Cutome-
ter has some limitations; for example, the pressure of the operator during measurement,
the temperature and humidity of the environment, the test position of the subject, and
the maintenance of the instrument will all affect the results [
18
,
23
]. The results may also
be influenced by the subject’s skin condition and environmental factors, such as health
status, temperature, and humidity. Variations in these conditions can affect skin properties
like hydration and elasticity, thus impacting the accuracy and reproducibility of the mea-
surements. While the Cutometer offers various parameters, the biological significance and
clinical relevance of some of these parameters are not always clear, and further research
is needed to better interpret and validate these measurements. With the advancement of
technology, new skin measurement techniques and devices, such as optical coherence to-
mography (OCT) and multiphoton tomography (MPT), are emerging. For specific research
objectives, it may be necessary to combine these techniques to obtain a more comprehensive
assessment of skin conditions.
The Cutometer plays a significant role in practical applications, yet there are inconsis-
tencies in the understanding and application of its tested parameters. In recent years, some
internationally renowned cosmetics companies have focused on efficacy evaluations of
their products and made these a necessary condition for product launch, further promoting
the development of relevant industry group standards. In human efficacy evaluation tests,
the R0 or F4 values may be used to evaluate skin firmness, while the R2, R5, or R7 values
can serve as parameters for skin elasticity and the Q parameters may be applied to assess
tightening efficacy. Based on previous experience, the trends of these parameters may differ
during project testing. For instance, in terms of elasticity, R2 values may show a significant
difference, while R5 values do not. This highlights the variability in practical applications.
Studies show that the R2, R5, and R7 parameters are associated with anti-aging, while
R4, R6, and R7 are correlated with age [
24
–
26
]. Additionally, some studies have utilized
Cutometer parameters to improve or summarize the methods for evaluating skin elasticity
and firmness [
27
]. However, most of the existing research focuses primarily on the R
parameters, and there is a lack of studies specifically addressing the facial skin of Chinese
women. This study utilizes the Cutometer to test the facial skin of multiple Chinese women
and analyzes the correlation between the measured parameters and age, discussing their
application in cosmetic efficacy evaluations. It aims to provide a reference for the use of the
Cutometer in skin research and cosmetic efficacy evaluations.
In summary, the Cutometer is a globally recognized tool for assessing skin elasticity,
offering valuable insights for skin research and cosmetic development. Although it has
certain limitations, its value in skin elasticity evaluations is undeniable. This study aims to
analyze the correlation between various viscoelastic parameters and age in Chinese women
by using the Cutometer. It specifically focuses on the effectiveness of relaxation phase
parameters in assessing skin elasticity. Additionally, the study examines the applicability
Cosmetics 2024,11, 205 3 of 13
and limitations of commonly used Cutometer parameters in evaluating skin firmness and
the anti-aging effects of cosmetic products.
2. Materials and Methods
2.1. Subjects
This study recruited 60 healthy Chinese female volunteers aged between 18 and
70 years, with an average age of 41.2 years, all residing in Eastern China. Before the start
of the experiment, all participants received detailed information regarding the study’s
purpose, procedures, potential risks, participant rights and obligations, as well as expected
benefits. Informed consent was obtained from all participants. The selection of subjects
was carried out strictly according to the methods outlined in Chapter 8 of the Cosmetic
Safety and Technical Standards (2015 Edition) for human efficacy evaluation (Table 1).
Table 1. Subject inclusion and exclusion criteria.
Criteria Details
Inclusion Criteria Exclusion Criteria
1
Willing to participate and provide
written informed consent;
2
Healthy females aged 18–70 years;
3
No use of anti-inflammatory drugs on
the test area in the past two months and
no laser treatment in the past three
months;
4
No participation in other clinical trials
in the past three months;
5
Skin in the test area must be free of
scars, birthmarks, atrophy, or other
conditions that could affect the test
results;
6
Ability to understand the study
requirements and willingness to
cooperate in completing all testing
procedures.
1
Use of antihistamines in the past week
or immunosuppressants in the past
month;
2
Currently undergoing facial treatment
or use of products to improve facial skin
condition in the past month;
3
Presence of untreated inflammatory
skin diseases;
4
Insulin-dependent diabetes;
5
History of cancer chemotherapy in the
past six months;
6
Immune deficiencies or autoimmune
diseases;
7
Participation in other clinical trials;
8
Pregnant or breastfeeding women.
These strict inclusion and exclusion criteria ensured the scientific rigor and reliability
of the study results, providing a standardized and well-controlled group for assessing the
efficacy of cosmetic products.
2.2. Instruments
The Cutometer Dual MPA 580, manufactured by Courage + Khazaka (Koln, Germany),
was used in this study to measure skin elasticity. The probe diameter was 2 mm, and the
software version was Cutometer Dual 2.1.2.1.
2.3. Methods
The laboratory environment was maintained at a constant temperature and humidity,
regulated by precision air-conditioning systems designed for human efficacy evaluation
experiments. The environment was continuously monitored by temperature and humidity
detectors. A total of 60 qualified subjects were selected based on the inclusion and exclusion
criteria. Before the experiment, participants were instructed to cleanse their faces using
a designated facial cleanser and dry their skin with non-woven paper towels. After the
cleaning, subjects waited for 30 min in this environment to stabilize their skin condition
before testing. This resting period of 30 min is in accordance with the requirements outlined
in Chapter 8 of the Cosmetic Safety and Technical Standards (2015 Edition) for human
efficacy evaluations.
Cosmetics 2024,11, 205 4 of 13
During the test, researchers used the Cutometer Dual MPA 580 to measure skin
elasticity on the cheekbone area of the face. The instrument was set to mode 1 with a
negative pressure of 450 mbar, and both the “on-time” and “off-time” were set to 2.0 s.
During the “on-time”, negative pressure was applied to draw the skin into the probe, and
during the “off-time”, the pressure was released, allowing the skin to gradually recover.
This suction-release cycle was repeated 10 times to collect skin elasticity data.
The test produced 22 viscoelastic parameters (R0–R9, Q0–Q3, F0–F4), which reflect the
biomechanical properties of the skin based on the displacement observed during the suction
and recovery phases. Detailed descriptions of the parameters and the corresponding skin
deformation curves are provided in Table 2and Figures 1–3[28].
Table 2. The available parameters for the Cutometer.
Parameter Name Parameter Description Parameter Significance
R0 = Uf Maximum deformation during
the first cycle
Represents the skin’s extensibility.
Ue Instantaneous deformation
Deformation 0.1 s after applying
negative pressure, reflecting the
skin’s immediate elasticity.
Ur Instantaneous retraction
The immediate retraction of the
skin after the release of negative
pressure.
Uv Delayed deformation
The skin’s deformation during the
delayed retraction phase,
reflecting the viscous component
of the skin.
R1 = Uf −Ua Remaining deformation after the
first cycle
The skin’s residual deformation
after the first cycle, indicating the
skin’s elastic limit.
R2 = Ua/Uf
Ratio of total retraction to
maximum deformation; total
elasticity
The ratio of total retraction to
maximum deformation,
representing overall skin elasticity.
A value closer to 1 indicates better
elasticity.
R5 = Ur/Ue
Ratio of instantaneous retraction
to instantaneous deformation; net
elasticity
The ratio of instantaneous
retraction to instantaneous
deformation, reflecting the skin’s
net elasticity.
R6 = Uv/Ue Ratio of delayed deformation to
instantaneous deformation
Reflects the ratio of viscous to
elastic components under
negative pressure.
R7 = Ur/Uf
Ratio of instantaneous retraction
to maximum deformation;
biological elasticity
The ratio of instantaneous
retraction to maximum
deformation, indicating the skin’s
biological elasticity.
R8 = Ua
Total retraction after the first cycle
The total retraction of the skin
after the first cycle.
Q0 Maximum deformation area The area under the curve for R0,
calculated as Q0 = 200 ×R0.
Q1 = QE/Q0
Ratio of the area formed by
instantaneous retraction to
maximum deformation area
Reflects the immediate elasticity
recovery.
Q2 = QV/Q0
Ratio of the area formed by
delayed retraction to maximum
deformation area
Reflects the delayed elasticity
recovery.
Cosmetics 2024,11, 205 5 of 13
Table 2. Cont.
Parameter Name Parameter Description Parameter Significance
Q3 = (QE + QV)/Q0
Ratio of total retraction area to
maximum deformation area;
overall elasticity
Indicates the overall elasticity of
the skin.
F0
The area between the actual curve
and the Uf value during the
negative pressure phase.
-
F1
The area between the actual curve
and the residual deformation (R1)
during the relaxation phase.
-
F2
The area between the actual curve
and R3 after 10 cycles of
deformation.
-
F3
The area between the upper and
lower curves after 10 cycles of
deformation.
-
F4
The total area under the upper
curve after 10 cycles of
deformation.
-
R3 Maximum deformation after
10 cycles
The maximum deformation of the
skin after the 10th cycle.
R4 Residual deformation after
10 cycles
The residual deformation after the
10th cycle.
R9 = R3 −R0
Difference between maximum
deformation in the 10th and
1st cycles
Represents the change in
maximum deformation between
the first and 10th cycles.
Cosmetics 2024, 11, x FOR PEER REVIEW 5 of 15
Q3 = (QE +
QV)/Q0
Ratio of total retraction area to
maximum deformation area;
overall elasticity
Indicates the overall elasticity of the
skin.
F0
The area between the actual
curve and the Uf value during
the negative pressure phase.
-
F1
The area between the actual
curve and the residual
deformation (R1) during the
relaxation phase.
-
F2
The area between the actual
curve and R3 after 10 cycles of
deformation.
-
F3
The area between the upper
and lower curves after 10 cycles
of deformation.
-
F4
The total area under the upper
curve after 10 cycles of
deformation.
-
R3 Maximum deformation after 10
cycles
The maximum deformation of the skin
after the 10th cycle.
R4 Residual deformation after 10
cycles
The residual deformation after the 10th
cycle.
R9 = R3 − R0
Difference between maximum
deformation in the 10th and 1st
cycles
Represents the change in maximum
deformation between the first and 10th
cycles.
Figure 1. Skin deformation curve obtained by one repetition.
Figure 2. Skin deformation curve obtained by ten repetitions.
Figure 1. Skin deformation curve obtained by one repetition.
Cosmetics 2024, 11, x FOR PEER REVIEW 5 of 15
Q3 = (QE +
QV)/Q0
Ratio of total retraction area to
maximum deformation area;
overall elasticity
Indicates the overall elasticity of the
skin.
F0
The area between the actual
curve and the Uf value during
the negative pressure phase.
-
F1
The area between the actual
curve and the residual
deformation (R1) during the
relaxation phase.
-
F2
The area between the actual
curve and R3 after 10 cycles of
deformation.
-
F3
The area between the upper
and lower curves after 10 cycles
of deformation.
-
F4
The total area under the upper
curve after 10 cycles of
deformation.
-
R3 Maximum deformation after 10
cycles
The maximum deformation of the skin
after the 10th cycle.
R4 Residual deformation after 10
cycles
The residual deformation after the 10th
cycle.
R9 = R3 − R0
Difference between maximum
deformation in the 10th and 1st
cycles
Represents the change in maximum
deformation between the first and 10th
cycles.
Figure 1. Skin deformation curve obtained by one repetition.
Figure 2. Skin deformation curve obtained by ten repetitions.
Figure 2. Skin deformation curve obtained by ten repetitions.
Cosmetics 2024,11, 205 6 of 13
Cosmetics 2024, 11, x FOR PEER REVIEW 6 of 15
Figure 3. Figure for Q parameters.
2.4. Statistical Analysis
Descriptive statistics for each indicator were obtained using R 4.2.2 software. The
Shapiro–Wilk Test was employed to assess the significance of data normality; a
significance level (two-tailed) greater than 0.05 indicates a normal distribution. A Pearson
correlation analysis was conducted to examine the relationship between the test indicators
and age, calculating the Pearson correlation coefficient and generating correlation
heatmaps and scaer plots, with a significance level set at α = 0.05.
3. Results
In this study, we performed a detailed analysis of skin elasticity parameters on the
facial skin of 60 healthy female volunteers using the Cutometer to investigate the
relationship between skin elasticity and age.
3.1. Correlation Analysis Results
Figure 4 presents a heatmap showing the correlation between 23 skin viscoelasticity
parameters and age. The heatmap visually represents the strength of the correlation for
each parameter. Generally, most parameters displayed a negative correlation with age,
with several demonstrating a significant inverse relationship. The depth of the colors in
the heatmap reflects the strength of the correlation, with darker shades indicating stronger
correlations and lighter shades indicating weaker or no correlation.
Figure 3. Figure for Q parameters.
2.4. Statistical Analysis
Descriptive statistics for each indicator were obtained using R 4.2.2 software. The
Shapiro–Wilk Test was employed to assess the significance of data normality; a significance
level (two-tailed) greater than 0.05 indicates a normal distribution. A Pearson correlation
analysis was conducted to examine the relationship between the test indicators and age,
calculating the Pearson correlation coefficient and generating correlation heatmaps and
scatter plots, with a significance level set at α= 0.05.
3. Results
In this study, we performed a detailed analysis of skin elasticity parameters on the fa-
cial skin of 60 healthy female volunteers using the Cutometer to investigate the relationship
between skin elasticity and age.
3.1. Correlation Analysis Results
Figure 4presents a heatmap showing the correlation between 23 skin viscoelasticity
parameters and age. The heatmap visually represents the strength of the correlation for
each parameter. Generally, most parameters displayed a negative correlation with age,
with several demonstrating a significant inverse relationship. The depth of the colors in
the heatmap reflects the strength of the correlation, with darker shades indicating stronger
correlations and lighter shades indicating weaker or no correlation.
Cosmetics 2024, 11, x FOR PEER REVIEW 6 of 15
Figure 3. Figure for Q parameters.
2.4. Statistical Analysis
Descriptive statistics for each indicator were obtained using R 4.2.2 software. The
Shapiro–Wilk Test was employed to assess the significance of data normality; a
significance level (two-tailed) greater than 0.05 indicates a normal distribution. A Pearson
correlation analysis was conducted to examine the relationship between the test indicators
and age, calculating the Pearson correlation coefficient and generating correlation
heatmaps and scaer plots, with a significance level set at α = 0.05.
3. Results
In this study, we performed a detailed analysis of skin elasticity parameters on the
facial skin of 60 healthy female volunteers using the Cutometer to investigate the
relationship between skin elasticity and age.
3.1. Correlation Analysis Results
Figure 4 presents a heatmap showing the correlation between 23 skin viscoelasticity
parameters and age. The heatmap visually represents the strength of the correlation for
each parameter. Generally, most parameters displayed a negative correlation with age,
with several demonstrating a significant inverse relationship. The depth of the colors in
the heatmap reflects the strength of the correlation, with darker shades indicating stronger
correlations and lighter shades indicating weaker or no correlation.
Figure 4. Correlation heatmap of 23 parameters (positive correlation in blue and negative correlation
in red).
Cosmetics 2024,11, 205 7 of 13
3.2. Top 10 Parameters with the Strongest Correlation with Age
Table 3lists the top 10 skin viscoelasticity parameters most strongly correlated with
age, along with their Pearson correlation coefficients. Ur (r =
−
0.66), R7 (r =
−
0.62),
and R8 (r =
−
0.60) exhibited the strongest negative correlations with age, suggesting
that these parameters significantly decrease with age, likely reflecting a decline in skin
elasticity. Q1
(r = −0.59)
, F3 (r =
−
0.59), and Q2 (r =
−
0.57) also demonstrated strong
negative correlations. Notably, R6 (r = 0.49) was the only parameter that showed a positive
correlation with age, indicating that this increases with age, potentially due to other
biomechanical changes associated with skin aging.
Table 3. The top 10 parameters with the strongest correlation with age.
Parameters Ur R7 R8 Q1 F3 Q2 R2 Ue R3 R6
Pearson correlation −0.66 **,1 −0.62 ** −0.60 ** −0.59 ** −0.59 ** −0.57 ** −0.56 ** −
0.51 **
−
0.49 **
0.49 **
1Indicates significant correlation at the 0.01 level (two-sided test). **: p≤0.01
3.3. Scatter Plot Analysis of Age with Ur, R8, and R7
Figure 5presents scatter plots of the relationship between age and threekey parameters
(Ur, R8, and R7):
Cosmetics 2024, 11, x FOR PEER REVIEW 8 of 15
Figure 5. Correlation curve between age and the three parameters: (a) scaer plots of Ur vs. age; (b)
scaer plots of R8 vs. age; (c) scaer plots of R7 vs. age.
4. Discussion
4.1. Analysis and Discussion of Ur, R7, R8, Q1, Q2, and R2
In this study, Ur had the strongest correlation with age among the 22 skin elasticity
parameters (r = −0.66, p < 0.01), followed by R7 and R8, with correlation coefficients of r =
Figure 5. Correlation curve between age and the three parameters: (a) scatter plots of Ur vs. age;
(b) scatter plots of R8 vs. age; (c) scatter plots of R7 vs. age.
Cosmetics 2024,11, 205 8 of 13
Ur vs. age (Figure 5a): The Ur values showed a clear and significant decline with age,
with a well-defined negative correlation (r = −0.66).
R8 vs. age (Figure 5b): R8 also exhibited a declining trend with age, with a relatively
concentrated distribution supporting its strong negative correlation (r = −0.60).
R7 vs. age (Figure 5c): Similarly, R7 decreased progressively with age, presenting a
strong negative correlation (r = −0.62), consistent with the data presented in Table 3.
4. Discussion
4.1. Analysis and Discussion of Ur, R7, R8, Q1, Q2, and R2
In this study, Ur had the strongest correlation with age among the 22 skin elasticity
parameters (r =
−
0.66, p< 0.01), followed by R7 and R8, with correlation coefficients of
r = −0.62
and r =
−
0.60, respectively. Scatter plots for Ur, R7, and R8 are shown in Figure 5.
These results align with previous research. Ryu et al. found that R7 had the strongest
correlation with age (r =
−
0.712) in their study on 96 healthy Korean women aged 20–75,
though R8 showed a weaker correlation (r =
−
0.261) [
26
]. In contrast, Ohshima et al.
identified R8 as the parameter most strongly correlated with age (r =
−
0.603), with R7 as
the second strongest (r =
−
0.510) [
16
]. Similarly, Luebberding et al. demonstrated that R7
had the highest correlation with age (r =
−
0.787) in their study on 150 Caucasian women,
while R2 also showed a strong negative correlation (r =
−
0.782); their study also found a
significant negative correlation between Ur and age (r =
−
0.692) [
29
]. Likewise, Krueger
et al. confirmed strong correlations between R7, Ur, and age in their research [
23
]. Therefore,
the results of this study regarding R7, R8, and Ur are consistent with previous findings. It
is worth noting that Ryu et al.‘s study did not find a strong correlation between R8 and age,
likely due to differences in ethnicity, skin type, or other physiological factors [26].
Table 3lists the 10 skin parameters with correlation coefficients |r| > 0.49 with age,
including Ur, R7, R8, Q1, F3, Q2, R2, Ue, R3, and R6. Notably, the first eight parameters
(Ur, R7, R8, Q1, Q2, R2, Ue, R6) were all derived from the first testing cycle, and the top
six parameters (Ur, R7, R8, Q1, Q2, R2) were associated with the relaxation phase. Ur, the
instantaneous retraction in the relaxation phase, had the highest correlation
(r = −0.66)
,
while R8 represented the total retraction during the relaxation phase. R2 and R7, respec-
tively, represent the ratio of total retraction (R8) to maximum deformation (Uf) and the
ratio of instantaneous retraction (Ur) to maximum deformation. In addition, Q1 and Q2
represent QE/Q0 and Qv/Q0, respectively, both of which are related to skin retraction
during the relaxation phase.
Therefore, retraction parameters during the relaxation phase, including Ur, R7, and R8,
serve as more reliable indicators of skin elasticity compared to suction-phase parameters.
This finding aligns with previous studies, which have demonstrated that relaxation-phase
parameters offer more accurate insights into skin elasticity, while suction-phase parameters
are more influenced by external factors, such as skin moisture or the use of cosmetic prod-
ucts [
14
,
16
,
18
,
21
,
22
]. Therefore, in skin elasticity studies and cosmetic efficacy evaluations,
greater emphasis should be placed on relaxation-phase parameters, particularly Ur, R7, and
R8, as they offer valuable reference points for predicting skin aging and elasticity changes.
4.2. Analysis and Discussion of R0, F4, F3, R3, and Ue Parameters
In skin firmness evaluations, R0 and F4 are commonly used as key indicators. R0
represents the maximum deformation during the first cycle, while F4 represents the total
area under the upper curve after 10 cycles. Typically, smaller R0 and F4 values indicate
firmer skin [
30
,
31
]. However, in this study, R0 and F4 demonstrated negative correlations
with age, with correlation coefficients of r =
−
0.47 and r =
−
0.48, respectively, suggesting
that younger skin had larger R0 and F4 values. This finding contrasts with the conven-
tional interpretation of these parameters in skin firmness assessments, where a significant
reduction in R0 or F4 after 28 days of product use is typically considered an improvement
in skin firmness in cosmetic efficacy studies.
Cosmetics 2024,11, 205 9 of 13
There is limited literature on the correlation between F4 and age, with most studies
focusing on the R, U, and F3 parameters. Since F4 represents the area under the upper
curve, it is theoretically strongly correlated with R0 (Uf), F3, and R3. In this study, F4
showed high correlations with Uf (r = 0.99), F3 (r = 0.89), and R3 (r = 1), indicating similar
trends. Numerous studies have reported significant negative correlations between R0,
F3, R3, and age [
16
,
26
,
28
,
32
,
33
], which aligns with the findings of this study. Therefore,
the negative correlation between F4 and age may not have been adequately addressed in
previous studies. It is important to note that this study used Cutometer Dual software
version 2.1.2.1, whereas in a newer version (MPA CTplus 1.1.6.4), F4 is defined as the area
under the lower curve (equivalent to F4-F3 in this study). In this updated version, F4
exhibited a weaker and less significant negative correlation with age (r =
−
0.259, p= 0.046).
Additionally, F3 showed a strong correlation with age (r =
−
0.59, p< 0.01). F3
represents the middle area between the upper and lower curves. As age increases, the
F3 area decreases, indicating that younger skin has greater resilience and recovers more
effectively after 10 cycles of deformation.
R0 represents the maximum deformation during the first cycle, while R3 represents
the maximum deformation after 10 cycles. In this study, R0 and R3 were significantly
positively correlated (r = 0.97, p< 0.01), and both showed negative correlations with age,
with correlation coefficients of
−
0.47 and
−
0.49, respectively. These results are consistent
with the findings of Ohshima et al., who observed a decrease in R0 and R3 in facial skin with
increasing age [
16
]. This phenomenon may be related to Ue (instantaneous deformation),
which reflects the skin’s elasticity under suction and is associated with skin thickness
and firmness. In contrast, Uv represents delayed deformation, primarily reflecting the
skin’s viscoelasticity. Younger skin typically has higher Ue values, indicating stronger
elastic recovery, and since R0 is the sum of Ue and Uv, younger skin tends to exhibit larger
R0 values.
It is important to note that R0 reflects not only the skin’s elastic recovery but also its
extensibility or expandability. Studies have shown that the use of moisturizers or emollients
can increase both Ue and Uv, due to the softening of the skin and the increased plasticity of
the epidermis [
12
,
16
,
33
]. Therefore, interpreting R0 solely as a measure of skin firmness,
with lower values being better, can be misleading. In certain cases, particularly in imme-
diate post-application evaluations, products that increase skin firmness may reduce the
maximum deformation under suction, leading to a lower R0 value. Thus, the interpretation
of R0 needs to be context-dependent, and the evaluation of skin firmness should consider
other parameters as well as the specific skin condition.
In conclusion, while R0 and F4 are widely used in firmness evaluations, their rela-
tionship with skin elasticity and firmness may vary in different contexts. Future research
should further explore the behavior of R0 and related parameters under different skin
conditions and product applications to better understand their reflection of skin’s biome-
chanical properties.
4.3. Analysis and Discussion of R2, R5, R6, and R7 Parameters
In skin elasticity testing, R2, R5, and R7 are three key parameters that are commonly
measured by the Cutometer to represent different aspects of skin elasticity. R2 indicates
total elasticity (Ua/Uf), R5 represents net elasticity (Ur/Ue), and R7 reflects biological
elasticity (Ur/Uf). The closer the correlation values are to 1, the better the skin’s elasticity.
In this study, R2, R5, and R7 showed correlations with age of r =
−
0.56, r =
−
0.32, and
r =
−
0.62, respectively, with R7 demonstrating the strongest negative correlation. These
results suggest that biological elasticity is the most significantly affected parameter with
advancing age, consistent with previous findings by Ryu et al., who identified R7 as one of
the most sensitive parameters for skin aging in Korean women [26].
R6 (Uv/Ue) represents the ratio of the viscous component to the elastic component of
the skin, specifically the ratio of delayed deformation to instantaneous deformation. In this
study, the R6 values for all 60 participants were less than 1, indicating that instantaneous
Cosmetics 2024,11, 205 10 of 13
deformation (Ue) was greater than delayed deformation (Uv), with the elastic component
dominating. Furthermore, R6 was positively correlated with age (r = 0.49, p< 0.01),
indicating that as age increases, R6 rises. This suggests that the viscous component of the
skin increases with age, while the elastic component decreases. The increase in R6 is linked
to the decline in Ue and the rise in Uv, a trend observed in previous studies on skin aging.
Similar patterns have also been observed in studies of photoaged skin [18,26,33–35].
R2, R5, and R7 reflect different dimensions of skin elasticity. R2, as a measure of
total elasticity, integrates the total deformation and maximum deformation, providing a
comprehensive assessment of overall skin elasticity. R5 indicates net elasticity, focusing on
the skin’s recovery ability, particularly the relationship between immediate retraction and
elastic recovery. R7, which reflects biological elasticity, captures the relationship between
maximum deformation and immediate retraction, making it a key parameter in anti-aging
research. The study found that R7 had the strongest correlation with age, highlighting its
importance as the most sensitive indicator of skin aging. This further supports the notion
that biological elasticity is the most responsive feature in the aging process [36–39].
Overall, the increase in R6 and the decrease in R7 together reflect the transition in aging
skin from strong elastic recovery to enhanced viscous properties. As skin’s viscoelasticity
increases, its ability to return to its original state diminishes significantly. These findings
are consistent with other aging-related studies, which show that skin gradually shifts from
being predominantly elastic to being more viscous with age [3,40–42].
This study confirms the significance of R2, R5, R7, and R6 in evaluating skin elasticity
and the aging process, particularly emphasizing R7 as a sensitive marker for skin aging
and the efficacy of anti-aging products. The positive correlation of R6 further supports its
role in understanding changes in skin viscoelasticity, highlighting the importance of the
viscous component as a key factor in skin aging.
4.4. Future Directions
Alterations in skin elasticity and firmness serve as critical indicators of skin aging.
A deeper understanding of the role of skin elasticity in the physiological aging process
can inform the development of more effective anti-aging treatment strategies. In recent
years, the widespread use of non-invasive skin measurement instruments has allowed
for the assessment of skin aging characteristics from multiple dimensions, such as the
physiological parameters of the skin surface, including pigmentation, barrier function, and
glossiness. Moreover, skin imaging technologies—such as ultrasound imaging, optical
coherence tomography, confocal microscopy, and two-photon microscopy—can be used to
visualize aging characteristics at various depths of the skin [43].
This study analyzes the mechanical characteristics of aging solely based on Cutometer
test parameters, with a research sample limited to Chinese women. It is recommended
that the sample size is expanded and studies on skin are conducted that include different
ethnicities and genders. Additionally, combining measurements from skin hardness testers,
skin moisture analyzers, skin oil content testers, and skin imaging technologies could
help investigate the correlation between Cutometer parameters and skin softness, hydra-
tion levels, oil content, and structural characteristics, providing a more comprehensive
understanding of the mechanical properties of skin aging. Furthermore, the effects of mois-
turizers, film-forming agents, and emollients in cosmetics on the mechanical properties of
the skin could also be explored.
5. Conclusions
By using the Cutometer to assess the skin elasticity parameters of 60 Chinese women,
this research analyzed the correlation between 22 viscoelastic parameters and age. The
results showed that, except for R6, all other parameters were negatively correlated with age.
Ur, R7, R8, Q1, Q2, and R2 exhibited the strongest correlations, with Pearson correlation
coefficients of
−
0.66,
−
0.62, and
−
0.60, respectively. These parameters were all associated
with the relaxation phase during testing, indicating that relaxation-phase parameters
Cosmetics 2024,11, 205 11 of 13
provide a more accurate reflection of skin elasticity compared to suction-phase parameters.
This aligns with previous studies, further validating the importance of the relaxation phase
as a sensitive stage for skin elasticity evaluations.
The study also found that R0 and F4 were negatively correlated with age (r =
−
0.47,
r =
−
0.48), with younger skin showing higher R0 and F4 values. However, in practical
applications, lower R0 and F4 values typically indicate firmer skin. Since R0 reflects skin
extensibility or expandability and is closely related to skin hardness and thickness, mois-
turizers, and emollients may reduce R0 and F4 values by softening the stratum corneum
or increasing epidermal extensibility. Therefore, relying solely on decreases in R0 or F4
to assess skin firmness may not be sufficient; it is necessary to consider the skin’s specific
condition and product use in a more detailed analysis.
Additionally, R2, R5, and R7, representing total elasticity, net elasticity, and biological
elasticity, respectively, were all significantly negatively correlated with age, with correlation
coefficients of
−
0.56,
−
0.32, and
−
0.62. R7 showed the strongest correlation, indicating that
biological elasticity is the most sensitive indicator of aging. This is consistent with the previous
literature, where R7 is widely used for assessing skin elasticity in anti-aging research.
R6, representing the ratio of the skin’s viscous component to its elastic component, was
positively correlated with age (r = 0.49, p< 0.01). This suggests that as age increases, the
viscous component of the skin gradually increases, while the elastic component diminishes,
further confirming the trend of elastic and viscoelastic changes during skin aging. The
increase in R6 serves as an effective marker for the increasing proportion of viscoelasticity
in aging skin.
In summary, the correlation analysis of multiple Cutometer parameters with age
underscored the importance of relaxation-phase parameters in assessing skin elasticity,
identifying R7 as a sensitive marker for skin aging. The limitations of R0 and F4 in
evaluating skin firmness further emphasize the need for a comprehensive evaluation.
These findings provide robust data support and a theoretical foundation for applying the
Cutometer in skin aging research and cosmetic efficacy evaluations.
Author Contributions: D.C.: Conceptualization, methodology, software, validation, formal analysis,
investigation, resources, writing—original draft, visualization, project administration, funding ac-
quisition; X.L.: data curation; H.F.: data curation; S.Y.: writing—original draft, writing—review and
editing, visualization, supervision; H.G.: supervision; S.Z.: supervision. All authors have read and
agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: This study was conducted in accordance with the Declaration
of Helsinki and approved by the Ethics Committee of the Charité—Universitätsmedizin Berlin
(protocol code EA1/190/19, approved on 9 August 2019).
Informed Consent Statement: Informed consent was obtained from all subjects involved in this study.
Data Availability Statement: The data presented in this study are available upon request from the
corresponding author.
Acknowledgments: Thank you to all the participants in this study.
Conflicts of Interest: The authors Dandan Chen, Shipeng Yin, Xuelian Lu, Haokun Fu and Hongqi
Gao are employees of Shanghai Forest Cabin Biological-Tech Co., Ltd. The authors declare that the
research was conducted in the absence of any commercial or financial relationships that could be
construed as a potential conflict of interest. The funders had no role in the design of the study; in the
collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to
publish the results.
Cosmetics 2024,11, 205 12 of 13
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