Pattern analysis using lower body human walking data to identify the gaitprint.

All people have a fingerprint that is unique to them and persistent throughout life. Similarly, we propose that people have a gaitprint, a persistent walking pattern that contains unique information about an individual. To provide evidence of a unique gaitprint, we aimed to identify individuals based on basic spatiotemporal variables. 81 adults were recruited to walk overground on an indoor track at their own pace for four minutes wearing inertial measurement units. A total of 18 trials per participant were completed between two days, one week apart. Four methods of pattern analysis, a) Euclidean distance, b) cosine similarity, c) random forest, and d) support vector machine, were applied to our basic spatiotemporal variables such as step and stride lengths to accurately identify people. Our best accuracy (98.63%) was achieved by random forest, followed by support vector machine (98.40%), and the top 10 most similar trials from cosine similarity (98.40%). Our results clearly demonstrate a persistent walking pattern with sufficient information about the individual to make them identifiable, suggesting the existence of a gaitprint.

NONAN GaitPrint: An IMU gait database of healthy young adults.

An ongoing thrust of research focused on human gait pertains to identifying individuals based on gait patterns. However, no existing gait database supports modeling efforts to assess gait patterns unique to individuals. Hence, we introduce the Nonlinear Analysis Core (NONAN) GaitPrint database containing whole body kinematics and foot placement during self-paced overground walking on a 200-meter looping indoor track. Noraxon Ultium MotionTM inertial measurement unit (IMU) sensors sampled the motion of 35 healthy young adults (19-35 years old; 18 men and 17 women; mean ± 1 s.d. age: 24.6 ± 2.7 years; height: 1.73 ± 0.78 m; body mass: 72.44 ± 15.04 kg) over 18 4-min trials across two days. Continuous variables include acceleration, velocity, position, and the acceleration, velocity, position, orientation, and rotational velocity of each corresponding body segment, and the angle of each respective joint. The discrete variables include an exhaustive set of gait parameters derived from the spatiotemporal dynamics of foot placement. We technically validate our data using continuous relative phase, Lyapunov exponent, and Hurst exponent-nonlinear metrics quantifying different aspects of healthy human gait.

Characterization of Adult Heart Rate Responses During Recreational Skateboarding at Community Skateparks.

Youth participating in recreational skating at community skate parks attain exercise intensities and durations that are comparable with the CDC's exercise recommendations for cardiovascular fitness for their age group. However, it is currently unclear if adults who skateboard in the same environment also achieve the recommended intensities and durations for cardiovascular fitness. Therefore, the purpose of this study was to test the hypothesis that skateboarding would elicit heart rates and durations consistent with the CDC's recommendations for cardiovascular fitness in adults. Fifty-five subjects between ages 18-55 were recruited from six community skateparks for this study. Subjects completed a questionnaire and were instrumented with a Polar V800 heart rate receiver on the left wrist and an H7 Bluetooth heart rate transmitter around the chest below the pectoralis major. Participants were instructed to engage in a typical skateboarding session on their own board with the duration and intensity of activity to be determined by the participant. The mean age of the participants was 27.4 ± 8.5 years, and participants reported skateboarding at a community skate park a mean of 3.1 ± 1.8 days/week. Participants had a mean heart rate of 138.2 ± 21.9 beats per minute (71.7% of age predicted maximum), skated for 65.5 ± 36.2 minutes, and traveled 4.56 ± 4.5 kilometers. Subjects spent 70% of their total duration at moderate-intensity or above and 30% within the low, and below low-intensity range. Results from this study suggest that adults participating in recreational skateboarding in community skateparks achieve the CDC's exercise recommendations for cardiovascular fitness. These findings may have implications for community skatepark design and professional training programs for adult skateboarding athletes.

Impact of Velcro Cuff Closure on Forearm Skin Temperature in Surfers Wearing a 2 mm and 3 mm Wetsuit.

Surfing is a worldwide sport that often requires participants to wear a wetsuit to assist in thermoregulation. In a recent study, forearm skin temperature decreased by approximately 3°C while wearing a wetsuit during recreational surfing. The purpose of this study was to test the hypothesis that reducing water flow in and out of the wetsuit by cuffing the wetsuit at the wrist, with a novel cuff closure system (Velcro cuff), would result in greater forearm skin temperature while surfing. One hundred and twelve (94 male, 18 female) recreational surfers between the ages of 18-50 participated in this study. Forearm skin temperature was measured at 1-minute intervals across the surf session in both arms with four wireless iButton thermal sensors located two inches from the styloid process (wrist) and olecranon process (elbow). Following instrumentation, all subjects had one of their wrists randomly cuffed with a one-inch wide Velcro cuff that was tightened to 2 cm less than the circumference of the wrist plus wetsuit. Subjects were then instructed to engage in regular recreational surfing activities for a minimum of 30 minutes at seven beaches in North San Diego County from October to April. No significant differences were found between the average cuffed wrist skin temperature and the average uncuffed wrist skin temperature (p = 0.06). However, average cuffed forearm skin temperature was significantly higher than average uncuffed forearm skin temperature (p = 0.01). Results from this study suggest that cuffing the wrist of wetsuits is a simple technique that can be utilized by surfers to significantly improve forearm skin temperature during surfing. These findings may also have an implication on future wetsuit designs.