The Effect of Fatigue and Biofreeze® on the Biomechanics of Running

Delayed onset muscle soreness (DOMS) is a common complaint of many runners, from novice to expert. DOMS can affect the primary movers in locomotion, including but not limited to the hip flexors and extensors, knee flexors and extensors, and the ankle plantar flexors. When running with DOMS, hip, knee, and ankle mechanics can be affected in such that they may cause protective compensation in order to prevent further damage or attenuate pain in the affected musculature. One common occurrence is DOMS in the knee extensors following prolonged running. DOMS occurring in the knee extensors can greatly affect sagittal knee joint biomechanics (Dutto and Braun 2004; Paquette et al., 2017). More specifically, these changes in knee mechanics can increase knee stiffness at initial stance, resulting in an increase in vertical leg stiffness. This change in knee stiffness potentially serves as a protective compensation mechanism against lengthening of the knee extensors (Paschalis et al., 2007; Tsatalas et al., 2010). Changing running mechanics (as a result of DOMS, or fatigue) can potentially lead to an increased risk of running related injury.

One potential way to reduce or alleviate the influence of muscle soreness on running biomechanics is via topical analgesic (Ellis et al., 2005). Topical analgesics, such as Biofreeze® work by attaching to the pain receptors that transmit a signal to the brain and relay a signal back to the muscle to protect the muscle by staying in a shortened position, affecting both force production and running biomechanics (Johar et al., 2012). The blocking of this signal should allow the individual to alleviate muscular pain and return muscle function and joint mechanics to pre-DOMS levels. However, the interactive effect of muscle soreness and a topical analgesic on the biomechanics of running remains unknown. A reduction in muscular pain related to DOMS can lead to improved performance in running, or at least more comfortability in daily living when dealing with DOMS. To date, there has been little research on the interactive effect of DOMS treated with a topical analgesic on running biomechanics.

Experiment protocol

Subjects: Twenty subjects aged 17-40 years will be recruited for the study. Participants will be considered recreational runners (minimum 17 years old, running 20km per week with no recent or current injuries). Written informed consent will be obtained from all subjects.

Experimental Procedures: Before any experimental procedures, participants will be a short familiarization session and anthropometric measurements that required for motion capture analysis will be taken. Next, participants will be allowed to warm up with their regular walk/run/stretching routine. After completion, participants will be instrumented with our biomechanics equipment (see below). Next, participants will run on a treadmill. Each running session will last for 5-10 minutes and participants will run at two different speeds (2 and 3 m/s) because the effects of eccentric exercise of both knee extensors and flexors on particular tempo-spatial parameters and knee kinematics of running are speed-dependent. Following the running session at both speeds, participants will perform our DOMS protocol (see below). At 48 hours post DOMS protocol, participants will return to the lab for the exact same running protocol as described above. Next, participants will have Biofreeze® (or placebo) applied (see below) and 15 minutes following the application, participants will again perform the running protocol (see timeline below)