Because serum cartilage oligomeric matrix protein (COMP) has been used to reflect articular cartilage condition, we aimed to identify walking and running mechanics that are associated with changes in serum COMP. Eighteen subjects (9 male, 9 female; age=23 ± 2 yrs.; mass=68.3 ± 9.6 kg; height=1.70 ± 0.08 m) completed 4000 steps on an instrumented treadmill on three separate days. Each day corresponded to a different ambulation speed: slow (preferred walking speed), medium (+50% of slow), and fast (+100% of slow). Synchronized ground reaction force and video data were collected to evaluate walking mechanics. Blood samples were collected pre-, post-, 30-minute post-, and 60-minute post-ambulation to determine serum COMP concentration at these times. Serum COMP increased 29%, 18%, and 5% immediately post ambulation for the fast, medium, and slow sessions (p<0.01). When the speeds were pooled, peak ankle inversion, knee extension, knee abduction, hip flexion, hip extension, and hip abduction moment, and knee flexion angle at impact explained 61.4% of total variance in COMP concentration change (p<0.001). These results indicate that (1) certain joint mechanics are associated with acute change in serum COMP due to ambulation, and (2) increased ambulation speed increases serum COMP concentration.

Four of the most popular modes of aquatic exercise are deep water (DW) exercise, shallow water (SW) exercise, water calisthenics (WC), and underwater treadmill (UT) exercise. The mechanical requirements of each aquatic exercise mode may elicit different physiological and biomechanical responses. The purpose of this descriptive literature review was to evaluate some biophysical differences between aquatic and land-based exercises. The biophysical variables reviewed included oxygen consumption (VO 2), heart rate (HR), rating of perceived exertion (RPE), stride length, stride frequency, pain, and measures of functional gain. Based on the studies reviewed, when compared with similar land-based exercises, VO 2 and HR maximum values were lower during DW and SW exercise, but, depending on water depth and exercise performed, may be greater during WC and UT exercise. RPE during DW exercise was generally similar to land exercise during max effort. Stride frequency tended to be lower for all four aquatic exercises, relative to onland counterparts. Pain levels tended to be similar between WC and land exercise, yet may decrease after UT exercise.

Experimental knee pain alters activation amplitude of various lower-extremity muscles during landing and jumping. The nature of the alteration varies between muscles, intensities, and phases of the movement (ie, landing and jumping). Generally, experimental knee pain inhibits the gastrocnemius, medial hamstring, and gluteus medius during landing while independently increasing activation of the same muscles during jumping.

During a 30-min run, AKP acutely alters midstance VM, VL, and GA EMG amplitude. AKP during a 30-min run does not, however, acutely influence articular cartilage metabolism.

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