Differences in Rate of Recovery Between Young and Middle-aged Men After Downhill Running

MVC (kg) measures the greatest amount of tension a muscle can generate and hold. We will measure it before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in MVC over time will be made between the two study's arms .

VJ (cm) is the height achieved after a vertical jump.We will measure it before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in VJ over time will be made between the two study's arms .

Stride length (cm) is the distance achieved while walking or running and is calculated as the distance from the toe of your right foot (starting position) to the toe of your right foot (ending position). Participants will run on a treadmill with pressure sensors for 2 minutes. We will measure stride length before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in stride length over time will be made between the two study's arms .

Stride frequency (strides per minutes) is the number of times a single foot hits the ground while walking or running. Participants will run on a treadmill with pressure sensors for 2 minutes. We will measure stride frequency before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in stride frequency over time will be made between the two study's arms .

Concentration of circulating IL-6 (pg/ml) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Concentration of circulating IL-10 (pg/ml) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Concentration of circulating IL-1ra (pg/ml) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Concentration of circulating TNFa (pg/ml) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Concentration of circulating CRP (nmol/L) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Concentration of circulating CK (IU/L) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Concentration of circulating LDH (IU/L) will be measured before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in concentration of circulating IL-6 over time will be made between the two study's arms .

Muscle fibers morphology of the Musculus quadriceps femoris will be assessed by Diffusion Tensor Imaging by magnetic resonance imaging (MRI). We will assess muscle fiber morphology before (baseline) and 48 hours after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in muscle fiber morphology over time will be made between the two study's arms .

DOMS will be evaluated using the Visual Analogue Scale (VAS). The VAS scale will be 150 mm line with "no pain" on one side and "maximal pain" on the other. Each participant will mark a line based on his soreness in the Musculus quadriceps femoris and Musculus gastrocnemius. The distance (mm) from the "no pain" side will be measured. DOMS assessment will be made before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point.

Changes in mood state will be assessed using the Profile of Mood States questioner (POMS). POMS is a validated questioners comprised from 58 feelings and emotions. For each parameter, the participants will be asked how he feels right know and select a value ranging between 0 to 4, where "0" means "not at all" and "4" means "extremely". A Total Mood Disturbance (TMD) score is calculated by summing the totals for the negative sub-scales and then subtracting the totals for the positive sub-scales.

Changes in total fatigue will be assessed using the Rating Of Fatigue scale (ROF). ROF is a validated 11-point numerical scale ranging from zero to ten. Participants will be asked to rate how fatigued they feel whereas, "0" is "not fatigued at all" and "10" is "Total fatigue and exhaustion- nothing left". Total fatigue assessment will be made before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point.

We will measure none-specific muscle fatigue using hand gripper to evaluate the forearm MVC (kg). We will measure it before (baseline) and after the downhill running protocol. Changes from baseline will be calculated for each time point. A comparison of the changes in MVC over time will be made between the two study's arms .

HRV (ms) quantifies the variability between heart beats. We will use the time-based analysis and the root mean square of successive differences of R-R intervals (RMSSD) value. The measurements will be done continuously with a heart rate monitor. Baseline measurements will be done for 3 to 5 days before the downhill running and the average value will be defined as "baseline HRV". Changes in HRV will be measured continuously in the 48 hours following the running. Percentage from "baseline HRV" will be calculated and compared between the two study's arms.