Week 5 - EMG Assignment-1 (1)

KIN 359 - Lab 2 – Electromyography Assignment – 45 points Data presentation : 1. Display the data from just your group in 3 tables: 1 ) Amplitudes of each pushup trial for all three positions for both participants, as well as the mean and %max; 2 ) leg extension resistance settings used for this exercise; and 3 ) Mean and %MVIC for each intensity used for leg extension exercise. 1) Table 1: Table 1 – Pushups Participant 1 Participant 2 Position  Wide Narrow Diamond Wide Narrow Diamond Trial 1 3.173 2.648 2.058  1.961 2.135  2.047 Trial 2 2.602 2.405 2.661  1.492 2.276  2.097 Trial 3 2.345 2.367 2.725  1.487 2.538  1.651 Mean (mV) 2.70 2.47 2.481 1.64 2.32 1.93 St Dev .423 .152 .368 .2722 .205 .2443 %max 2.70 .914 .918 1.64 1.415 1.18 2) Table 2: Table 2 – Leg Extension Resistance Settings Intensity  1RM (lbs) 10% (lbs) 25% (lbs) 50% (lbs) 75% (lbs) 125% (lbs) Subject 1 70 5 lbs 20  35 50 85 3) Table 4: Table 4 – Leg Extension – Mean Amplitude and % MVIC Record data below in mV Intensity  MVIC 10% 25% 50% 75% Vastus lateralis Mean (mV) 1.866 .30 1.1215  1.538 1.796 % MVIC 125% 30% 60.1% 82.4% 96.2% Biceps Femoris Mean (mV) .745 .563 .563 .512 .538 % MVIC 125% 75.6% 75.6% 68.7% 72.2% Vastus medialis Mean (mV) 1.42 .501 1.231 1.141 .965 % MVIC 125% 35.3% 86.7% 80.4% 68%

2. Using data from the entire class (8 subjects), calculate the mean and standard deviation of the EMG ( as % max ) for each pushup position. Present these data in a bar graph (3 bars on 1 graph). wide narrow diamond 84% 85% 86% 87% 88% 89% 90% 91% 92% 93% Mean EMG % Max for Pushup Position Pushup Postion Mean EMG % Max Position wide narrow diamond Mean 87% 87% 92% Std 0.14269739 0.14349713 0.09237772 3. Using data from all 4 groups , calculate the mean and standard deviation of the EMG (% MVIC ) for each leg extension intensity. Present these data in a line graph (1 line for each muscle group). 10% 25% 50% 75% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mean EMG %MVIC For Leg Extension Vastus Lateraris Biceps Femoris Vastus Medialis Leg Extension Intensity % MVIC(%)

During the push up test when you are in a wider position, your pectorals major is being used for the lower activation of your triceps as well as the deltoids. When you are doing a push up from the diamond shape your back muscle and abdominal muscles are more activated than the triceps. In lab we could see that when doing the diamond shape pushups some people lose their form because they are using the majority back and abdominals in the diamond position. 6. Discuss how you could use this information (#4/5) in your personal life or professional career. By knowing which pushup position produces the greatest triceps brachii activation is important when doing fitness testing during physical education classes. For example, if I wanted the class to target more triceps brachii and pectoralis major, I would have the students perform wide pushups. If I wanted the students to target more triceps brachii, then I would have the students do the narrow or diamond pushups. By learning this information, I will be able to offer my advice on what pushups would be best depending on what muscle group they want to work. 7. Based on class data, which quadriceps muscle studied appears to be most activated during knee extension? Does one muscle have a higher relative activation (%MVIC) at submaximal intensities? The quadriceps that are most activated during knee extension is the biceps femoris because they have a higher relative activation (%MIVC). During the knee extension as intensity increases, the vastus medialis and vastus lateralis take over the biceps femoris. At 10% intensity, the biceps femoris has a %MVIC of 46% and the vastus medialis and vastus lateralis have a %MVIC of 37% and 30%. At 75% intensity, the %MIVC for vastus lateraris was 85%, for vastus medialis it was 80%, and for biceps femoris at 75% it was 86%. By looking at the graph we can see that when the intensity increases, the vastus lateraris becomes more activated, then the vastus medialis, and the biceps femoris. 8. Based on class data, what is the relationship between force and EMG amplitude in the quadriceps? What is the strength of the correlation between the two (support with data)? What causes any observed changes in EMG amplitude as force or resistance changes? The relationship between force and EMG amplitude in the quadriceps is positive relatively linear as we can see in the graph in question 3. After calculating the correlation coefficient (R) for each muscle in the quadriceps vastus medialis, and vastus literalis we the value is R=.997, and R=.995. The correlation coefficient values indicate a strong positive relationship between the EMG and force amplitudes. Some things that may cause changes in EMG amplitude as force or resistance changes could be muscle fatigue, muscle fibers, and many other factors could cause a change. 9. Are the hamstring muscles activated during leg extension? Does intensity matter? How do you know/support your response? What term is used to describe this? The hamstrings are activated during leg extensions. When intensity is increased during leg extension your hamstrings have less importance when doing a leg extension. During leg extension the muscles that are being used are the quadriceps and they contract while the hamstrings are length. The term used to describe this is coactivation. 10. Explain why proper site preparation and electrode placement is critical for EMG. Site preparation and electrode placement is critical for EMG because if the site is not prepared well the electrode may not pick up the action potentials. Since there are different locations for the muscles this can also influence the signal quality that is received.