ABSTRACT

1. PHYSICAL WORKING CAPACTIY AT FATIGUE THRESHOLD IS ASSOCIATED WITH MEASURES OF PHYSICAL FUCTION IN OLDER ADULTS Nadia S. Emerson1, William P. McCormack1, Jeffery R. Stout1, Jay R. Hoffman1, Maren S. Fragala1, Tyler C. Scanlon1, David R. Williams1, Adam M. Gonzalez1, Gerald T. Mangine,1 Adam J. Wells1, Joel T. Cramer2 1Human Performance Laboratory, University of Central Florida, Orlando, FL; 2Oklahoma State University, Stillwater, OK ABSTRACT INTRODUCTION CONT. RESULTS RESULTS (CONT.) METHODS CONT. • To the best of our knowledge, no one has examined the relationship between the PWCFT to strength, body composition, and serum markers used to assess the physical health and nutritional status in older persons DETERMINATION OF PWCFT: The PWCFT values were determined using the EMG amplitude from the vastuslateralis muscle. 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 resting • Mean values ± the standard deviation are recorded below BACKGROUND: Physical function in older adults is often evaluated with measures of muscular strength, body composition, and circulating biomarkers, such as serum albumin and hemoglobin. The physical working capacity at fatigue threshold (PWCFT) test measures the ability to resist fatigue and has been associated with the health and functional capacity of older men and women. To the best of our knowledge, no one has examined the relationship between the PWCFT to strength, body composition, and serum markers used to assess the physical health and nutritional status in older persons. PURPOSE: This study examined the relationship between the PWCFT with common measures used to asses physical health in older persons. METHODS: Thirty-six healthy older men and women (age: 71.3±6.1 y; BMI: 27.9±5.2 kg∙m-2) volunteered to participate in this study. After an 8 to 12 hour fast the participants had their blood drawn and lean soft tissue mass (LST) measured by Dual-energy X-ray absorptiometry (Lunar, GE). The participants then performed the PWCFT test, a discontinuous, cycle ergometry test utilizing EMG fatigue curves to identify the power output corresponding to the onset of fatigue. Additionally, maximal isometric grip strength (GRIP) and sit-to-stand in 30 seconds (STS) were measured.RESULTS:Pearson’s correlation coefficient for PWCFT and other common measures of physical health and function are as follows: GRIP: r=.35; STS: r=.42; LST (kg): r=.33; Albumin (g/dL): r=.36; Hemoglobin (g/dL): r=.18. CONCLUSIONS: The PWCFT test demonstrated a significant but moderate relationship with all variables with the exception of hemoglobin. These data suggest that the PWCFT test may be related to physical health and nutritional status of older men and women in this study. PRACTICAL APPLICATION: The salient features of the PWCFT test are the ease of measurement, submaximal effort requirement, non-invasiveness, and reliability for measuring resistance to fatigue. Because of the positive relationship observed between the PWCFT and measures of strength, function and muscle mass, perhaps a clinician or personal trainer should consider adding the PWCFT test as an additional method monitor the effectiveness of an intervention (exercise or nutrition). Table 1. Mean Values of Measures of Physical Function PURPOSE • This study examined the relationship between the PWCFT with common measures used to assess physical health in older persons. Maximal Isometric Grip Strength Physical Working Capacity at Fatigue Threshold (PWCFT) METHODS heart rate return to within 20 bpm of that obtained upon arrival to the laboratory. During each 2 minute bout, six 10-second EMG samples were recorded from the vastuslateralis. 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. • The table below presents the correlation of PWCFTto various measurements. SUBJECTS: Thirty-six healthy older men and women (age: 71.3±6.1 y; BMI: 27.9±5.2 kg∙m-2) completed tests of muscular function including PWCFT, isometric grip strength (GRIP), and sit-to-stand in 30 seconds STS. BODY COMPOSITITON: Body composition was assessed by Dual-energy X-ray absorptiometry FASTED BLOOD DRAW: Fasting serum samples were collected and analyzed with a hematology analyzer to evaluate circulating hemoglobin and albumin. Table 2. Relationship Between PWCFT and Common Measures for Assessing Physical Health *significance (p≤ .05) SUMMARY & CONCLUSIONS • The PWCFT test demonstrated a significant but moderate relationship with all variables with the exception of hemoglobin. • These data suggest that the PWCFT test may be related to physical health and nutritional status of older men and women in this study. ELECTROMYOGRAPHIC (EMG) MEASUREMENTS : A bipolar (2.54 cm center-to-center ) surface electrode arrangement was placed on the right thigh over the lateral portion of the vastuslateralis muscle, midway between the greater trochanter and the lateral condyle of the femur. A reference electrode was placed on the lateral portion of the distal femur. Interelectrode impedance was kept below 5,000 ohms by careful abrasion of the skin. The EMG signal was preamplified using a differential amplifier. The EMG was sampled at 1,000 points/s and filtered at 10-500 Hz. The root mean EMG Amplitude values were calculated for the 10-s time frame for each sample taken. HAND 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. PRACTICALAPPLICATIONS • The salient features of the PWCFT test are the ease of measurement, submaximal effort requirement, non-invasiveness, and reliability for measuring resistance to fatigue. SIT TO STAND: From a seated positions with arms crossed over chest, subjects stood up and sat down for 30 seconds. PWCFT • Because of the positive relationship observed between the PWCFT and measures of strength, function and muscle mass, perhaps a clinician or personal trainer should consider adding the PWCFT test as an additional method monitor the effectiveness of an intervention (exercise or nutrition). INTRODUCTION • Physical function in older adults is often evaluated with measures of muscular strength, body composition, and circulating biomarkers, such as serum albumin and hemoglobin. • The physical working capacity at fatigue threshold (PWCFT) test measures the ability to resist fatigue and has been associated with the health and functional capacity of older men and women. STATISTICS: Pearson’s correlation coefficients were computed to assess the relationship between PWCFT and other measures of physical health and function. ACKNOWLEDGEMENTS EMG signal during 2 minute stage 30 second Sit to Stand *Sponsored by ABBOTT NUTRITION EMG analysis software