Transcript 72x36 Poster Template

Nadia S. Emerson1, Jeffrey R. Stout 1, FACSM, Edward H. Robinson 1, William P. McCormack 1, Tyler C. Scanlon 1, Ashlee M. Warren 2, Adam J. Wells 1, Adam M. Gonzalez 1, Gerald T. Mangine 1, Jeremy T.
Townsend 1, Adam R. Jajtner 1, Jay R. Hoffman1 and Maren S. Fragala 1
1 Institute
ABSTRACT
muscular strength and body composition, such as muscle quality (MQ) and skeletal muscle
index (SMI). The physical working capacity at fatigue threshold test (PWCFT) measures the
ability to resist fatigue and has been associated with the health and functional capacity of
older adults. Data suggests that individuals with a low SMI (women < 5.45 kg/m2 and men
< 7.26 kgm2) have an increased risk of physical disability.
Purpose: Examine relationships between PWCFT and common measures used to assess
physical health in older adults with low and high risk of physical disability as categorized by
SMI.
Methods: Fifty-eight older adults (age: 71.1±6.2 y; BMI: 28.0±5.4 kg/m2) were categorized
into low risk (n=36) or high risk (n=22) groups. Lean soft tissue mass (LST) and fat mass
(FM) were measured by DEXA and participants performed a discontinuous cycle ergometry
test to determine PWCFT. Maximal isometric grip strength (GRIP) and sit-to-stand (STS)
reps in 30 sec were measured. MQ was defined as GRIP relative to appendicular lean soft
tissue (ALST) and SMI as ALST/height2. Simple and Partial correlations, adjusting for fat
mass, were used to examine the relationships among dependent variables.
Results: The PWCFT showed significantly positive relationships with GRIP (r= 0.62, p<
0.001), STS (r= 0.50, p< 0.01), and LST (r= 0.61, p< 0.001) and a significantly negative
relationship with FM (r= -0.33, p< 0.05) only in the low risk group. PWCFT was not
significantly correlated to MQ (p> 0.05). When adjusting for FM, similar results were
observed between PWCFT and GRIP (r= 0.64, p< 0.001), STS (r= .41, p< 0.01), and LST (r=
0.61, p< 0.001) in the low risk group. No significant (p< 0.05) relationships were found for
the high risk group.
Conclusion: The PWCFT demonstrated a significant correlation with all variables of
physical function in the low risk group with the exception of MQ; however, no significant
relationships were seen in any of the variables for the high risk group. Our data suggest
that the PWCFT may be related to physical function in older adults with low risk of physical
disability, but may not be an appropriate measure for older adults with high risk of physical
disability.
INTRODUCTION
• Physical function in older adults is often
evaluated with measures of muscular
strength and body composition, such as
muscle quality (MQ) and skeletal muscle
index (SMI).
• Fifty-eight older adults (age: 71.1±6.2 y; BMI: 28.0±5.4 kg/m2) were included in
this analysis.
• Lean soft tissue mass (LST) and fat mass (FM) were measured by DEXA.
• DEXA derived appendicular lean soft tissue (ALST) was used to calculate SMI
with the formula:
SMI = ALST(kg) ∙ height (m)2
• A bipolar (4.6 cm center-to-center) surface electrode arrangement was placed
over the right vastus lateralis muscle, at approximately 60 percent of the
distance from the lateral portion of the patella on a line with the greater
trochanter.
1) To examine relationships between PWCFT and common measures used to
assess physical health in older adults with low and high risk of physical disability
as categorized by SMI
2) Evaluate the extent to which PWCFT and measures of physical function differ
between low and high RiskPD
Hand Grip (GRIP)
• Handgrip was measured with a hand dynamometer in the
standing position. Arms were adducted to sides with a 90
degree bend at the elbow. Three maximal isometric
contractions were performed for 3 to 5 seconds each. The
average of the three trials was recorded
• The initial work rate for each participant was set
at 30 W.
• The subjects began pedaling at 50 rpm on a
calibrated, electronically braked cycle ergometer.
• Power output was increased 10 to 20 W for each
two-minute stage of the discontinuous protocol.
• Rest intervals between bouts were sufficiently
long enough to allow heart rate to return within 20
bpm of resting heart rate.
EMG analysis showing
significant positive EMG
v. time slope indicating
onset of fatigue
0.29
-0.07
 PWCFT had a significant positive correlation to LST and significant negative
correlation to FM in low RiskPD (p< 0.05).
 No correlation was seen between PWCFT and body composition measures for
high RiskPD.
 MQ was not significantly correlated to PWCFT in either low or high RiskPD.
 After adjusting for FM, results remained the same for all variables.
30 second Sit to Stand
• Independent t tests were used to compare the mean PWCFT, GRIP, STS, LST,
and MQ of low RiskPD as compared to high RiskPD. Simple and partial
correlations, adjusting for fat mass, were used to examine the relationships
among dependent variables.
RESULTS
Table 1. Physical characteristics and performance measures of participants
(n = 58)
Low SMI /High RiskPD High SMI /Low RiskPD
(n = 22; 10M, 12F)
(n = 36; 15M, 21F)
Determination of PWCFT
• The PWCFT values were determined using the
EMG amplitude from the vastus lateralis muscle.
0.71**
0.06
 No significant relationships between PWCFT and measures of physical
function were seen in high RiskPD.
Sit-to-Stand (STS)
Statistical Analysis
EMG signal during a single 2-minute stage
0.17
-0.05
-0.12
0.61**
0.09
-0.33*
 PWCFT demonstrated significant correlations with all variables of physical
function in low RiskPD (p<0.05).
• From a seated position with arms crossed over chest,
subjects stood up and sat down as many times as
possible for 30 seconds.
• A reference electrode
was placed over the
lateral epicondyle of the
distal femur.
LST (kg)
MQ (kg)
FM (kg)
 There were no significant differences in GRIP (p=.318) and MQ (p= .096) between
low and high RiskPD groups.
(kg)/ALST(kg)-1]
Electromyography (EMG) Measures
High RiskPD
Correlation
Partial
0.07
0.12
0.09
0.13
 Independent t tests revealed significant differences (p< 0.05) in PWCFT, STS, and
LST for low RiskPD as compared to high RiskPD.
• Muscle quality (MQ) was defined as GRIP relative to ALST as recommended by
Porter et al. (1998) with the following formula:
• Lower body function was assessed by the number of sit-to-stand (STS)
repetitions in 30 seconds.
Low RiskPD
Measure
Correlation
Partial
GRIP (kg)
0.62**
0.64**
STS (# in 30 s) 0.50**
0.41*
SUMMARY & CONCLUSIONS
• Maximal isometric grip strength (GRIP) was assessed with a hand grip
dynamometer.
MQ = [GRIP
Table 2. Relationship between PWCFT and common measures for assessing
physical health in elderly at low and high risk of physical disability (RiskPD)
*p <0.05, **p ≤ 0.01
• Participants performed a discontinuous, incremental cycle ergometry test to
determine PWCFT.
• The EMG signals were expressed as root mean square (rms) amplitude values
(µVrms) by custom written software.
PURPOSE
During each 2 minute bout, six 10-second EMG samples were recorded from the
vastus lateralis. The PWCFT was determined by averaging the highest power output
that resulted in a nonsignificant (p>0.05) slope value for EMG amplitude vs. time
relationship and with the lowest power output the resulted in a significant (p≤0.05)
slope value.
Figure 1. Physical Working Capacity at Fatigue Threshold (EMG vs. Time)
• The raw EMG signals were pre-amplified using a differential amplifier, sampled
at 1,000 Hz, and stored on a laboratory computer for off-line analysis.
Physical Working Capacity at
Fatigue Threshold (PWCFT)
Determination of PWCFT cont.
• Participants were classified as high risk of physical disability (n=36) by SMI<
5.45 kg•m-2 for women and < 7.26 kg•m-2 for men; participants with SMI values
greater than these were classified as low risk (n=22) (Baumgartner et al. 1998).
• Inter-electrode
impedance was kept
below 5,000 ohms with
abrasion of the skin
beneath the electrodes.
• The physical working capacity at fatigue
threshold test (PWCFT) measures the ability
to resist fatigue and has been associated
with the health and functional capacity of
older adults.
RESULTS CONT.
METHODS CONT.
METHODS
Background: Physical function in older adults is often evaluated with measures of
• Data suggests that individuals with a low
SMI (women < 5.45 kg/m2 and men < 7.26
kg/m2) have an increased risk of physical
disability.
of Exercise Physiology and Wellness, University of Central Florida, Orlando, FL, 2Health Center, University of Central Florida, Orlando, FL
Physical characteristics
Age (years)
Height (cm)
Mass (kg)
BMI (kg/m2)
Performance measurements
PWCFT (W)
GRIP (kg)
STS (# per 30 s)
71.5 ± 6.3
166.8 ± 11.0
70.3 ± 18.5
24.9 ± 4.4
71.1 ± 6.3
165.8 ± 11.9
80.6 ± 17.4*
29.1 ± 4.4**
41.4 ± 20.9
30.4 ± 9.8
11.5 ± 4.0
58.5 ± 24.3**
32.4 ± 13.8
14.3 ± 4.5*
Values reported as mean ± SD; *p <0.05, **p ≤ 0.01 between low and high SMI
 The results of this study suggest that low RiskPD
rating as classified according SMI value resulted in
significantly higher performance measurements, with
the exception of GRIP, compared to high RiskPD.
 Furthermore, the PWCFT appears to be related to
measures of physical function and body composition
in low RiskPD, but not high RiskPD elderly.
 Our data suggest that classifying low or high RiskPD
using SMI appears to reflect muscle functionality.
 However, PWCFT was only related to physical
function in older adults with low RiskPD, and may
not be an appropriate measure for assessing
physical function in older adults with high RiskPD.
PWCFT
REFERENCES
1. Baumgartner RN, Koehler KM, Gallagher D, Romero L, Heymsfield SB, Ross RR, Garry PJ,
Linderman RD (1998) Epidemiology of sarcopenia among the elderly in New Mexico. Am J
Epidemiol 147:755-763..
2. Porter MM, Myint A, Kramer JF, Vandervoort AA (1995) Concentric and eccentric knee extension
strength in older and younger men and women. Can J Appl Physiol 20:429-439..