February 28, 2014

Ross Blesener '14Abstract:

Development of an Isometric Leg Strength System for Measurement of Maximal Voluntary Contraction Strength in the Elderly

Eric Lindahl '14Abstract:

Age-related frailty has been linked to loss of independence and functional mobility in the elderly. At present, there are ~40 million elderly persons in the US, a number that is projected to double by 2030. Therefore, reducing frailty in this population is of great importance. Currently, the clinical definition for a frailty phenotype consists of five frailty indicators: unintentional weight loss, low grip strength, low endurance, low activity levels, and slow walking speed. However, simpler, more objective ways to test for frailty could be useful, as earlier detection can lead to earlier intervention. PURPOSE: The purpose of this study was to construct an Isometric Leg Strength System (ILSS) to measure maximal voluntary contraction (MVC) strength of the knee extensor muscles, and study its effectiveness in assessing MVC as a possible frailty indicator. METHODS: Subjects (n=20; 14 male, 6 female) ranging in age from 19-71 (n=10 19-30 y; n=10 65-71 y) performed traditional frailty testing and completed health and activity questionnaires. The ILSS was then used to measure knee extensor MVC strength. Traditional frailty test results were analyzed to determine a frailty phenotype and were compared to the ILSS results. One-way ANOVA was performed to analyze differences between age groups, and Pearson product-moment correlations were used to analyze the connection between the results of the traditional frailty phenotype testing and MVC strength testing. RESULTS: While no significant correlation was found between the overall frailty phenotype and MVC strength, there was a significant correlation between MVC strength and hand grip strength (r=.59, p=.007). MVC strength was also significantly correlated with the subject’s height (r=.65, p=.002) weight (r=.71, p=.003), and BMI (r =.56 p=.01). No significant differences were found between the results of young and elderly participants. CONCLUSION: Although MVC strength and the frailty phenotype were not connected overall, MVC strength was significantly correlated with one of the 5 indicators (hand grip strength). In addition, the significant link between MVC strength and other physical characteristics adds validity to the ability of the ILSS to correctly measure strength differences between individuals. This study will be expanded to include less robust elderly participants who meet a higher number of frailty criteria so that a more conclusive connection between the clinical frailty indicators and MVC strength can be elucidated.

Seasonal and spatial variation in morphology of Daphnia: Defense against invertebrate predators

Alina Burks '14Abstract:

Morphological defense mechanisms like helmets are employed by Daphnia because of predation on the species by invertebrate predators (i.e. Chaoborus, Leptodora). Common defense mechanisms seen in Daphnia are helmets and tail spines. These morphological changes result in a trade off of shorter life span and less reproduction, therefore, they have been found to only be employed in areas densely populated with predators. This study focuses on samples of two species of Daphnia in Square Lake from 2010 taken at different levels of stratification throughout the summer. Ratios of helmet length to body length (HL:BL) and spine length to body length (SL:BL) were recorded. We expected the D. mendotae to exhibit larger HL:BL and SL:BL ratios than D. pulicaria, as they are smaller bodied and more vulnerable to invertebrate predators. We also expected to see HL:BL and SL:BL ratios to be greater in depths and times of year when invertebrate predators were in higher abundance. We found D. mendotae to have significantly larger HL:BL ratios than D. pulicaria and larger HL:BL later in the summer, which coincided with the number of invertebrate predators counted in the samples. We also found both species to have larger HL:BL ratios in the mid to late summer, but it was more pronounced in D. mendotae. Finally, we found both D. mendotae and D. pulicaria to have larger HL:BL ratios in the epilimnion of the lake than in deeper water. These findings support our expectations that Daphnia that are more vulnerable to predators would exhibit morphological defense mechanisms to a greater extent than larger bodied Daphnia and that Daphnia would have greater HL:BL and SL:BL ratios at the time and place where invertebrate predator abundance was greater.