Individuals must constantly modify their gait patterns to safely transition between different surfaces. The goal of the current study was to determine if gait changes could be detected two steps from a transition, and whether these changes scaled with the angle of the hill. We hypothesized that during the anticipation of uphill walking and the aftereffect of downhill walking, the magnitude of kinetic and electromyography changes would be greatest at steep hill angles and fewer steps from the transition. We collected force and electromy-ography data as participants walked on the level ground before an uphill ramp and after a downhill ramp. As hypothesized, there were significant main effects for both the number of steps and angle of the hill for the first vertical GRF peak, as well as lateral gastrocnemius and vastus lateralis activity. Overall, our results indicate that when transitioning to and from hills, anticipation and aftereffect responses occur at least two steps from the transition and are scaled to the angle of the hill.
Riley C. Sheehan and Jinger S. Gottschall
Keith A. Stern and Jinger S. Gottschall
The purpose of our study was to determine if altering the insoles within footwear or walking barefoot, as an attempt to increase or decrease cutaneous stimuli, would improve dynamic balance during a hill-walking task. We hypothesize that compared with foam insoles or iced bare feet, textured insoles or bare feet will result in greater speeds, longer step lengths, narrower step width, shorter stance time, and less tibialis anterior (TA), soleus (SOL), and lateral gastrocnemius (LG) activity during key gait cycle phases. Ten, healthy college students, 5 men and 5 women, completed the protocol that consisted of level walking and downhill transition walking in five different footwear insole or barefoot conditions. During level walking, conditions with the hypothesized greater cutaneous stimuli resulted in greater step length, which relates to a more stable gait. In detail, the texture insole condition average step length was 3% longer than the regular insole condition, which was 5% longer than the ice condition (p < .01). The same signals of increased stability were evident during the more challenging downhill transition stride. Step length during the barefoot condition was 8% longer than the ice condition (p < .05) and step width during the regular footwear condition was 5% narrower than the foam condition (p = .05). To add, during the preswing phase of level walking, TA activity of the textured insole condition was 30% less than the foam insole. Although our data show that footwear conditions alter gait patterns and lower leg muscle activity during walking, there is not enough evidence to support the hypothesis that textured insoles will improve dynamic balance as compared with other footwear types.
Riley C. Sheehan and Jinger S. Gottschall
Falls are the leading cause of injury for all age groups. However, adults over 65 are at a higher risk, with one-third falling each year. Transitioning between level and hill surfaces poses a greater fall risk than walking on either surface alone. Previous studies found that young adults adopted a cautious gait pattern to mitigate this risk. As older adults typically employ a cautious pattern during level walking, we investigated how they modify their gait pattern to safely transition between surfaces. Twenty adults over the age of 65 transitioned onto and off of a 15° ramp while we recorded kinematics and muscle activity. During the level-to-downhill and uphill-to-level transitions, participants took slower, shorter steps indicative of an exaggerated cautious gait pattern. The older adults also exhibited greater muscle activity during the transitions, which may be due to muscle weakness requiring compensatory strategies to meet the greater demands of the task. However, the slower, shorter steps when transitioning from uphill to level suggest that these compensations may not always be adequate. Thus, it is important to consider the relationship between physical abilities and task demands in evaluating walking terrains that may be excessively difficult or dangerous for older adults.
Riley C. Sheehan and Jinger S. Gottschall
In a previous study, we found that participants modified how they transitioned onto and off of ramp configurations depending upon the incline. While the transition strategies were originally attributed to ramp angles, it is possible that the plateau influenced the strategies since the final surface height also differed. Ultimately, for the current study, we hypothesized that an individual’s transition strategies would have significant main effects for ramp angle, but not plateau height. Twelve healthy, young adults transitioned onto 3 distinct ramp configurations, a 2.4-m ramp angled at 12.5° ending at a plateau height of 53 cm, a 1.2-m ramp angled at 23.5° ending at a plateau height of 53 cm, and a 2.4-m ramp angled at 23.5° ending at a plateau height of 99.5 cm. Kinematics, kinetics, and muscle activity were measured during the stance phase before contacting the ramp. In support of our hypothesis, impact peak, active peak, and all of the muscle activity variables had a significant main effect for ramp angle, with greater vertical force peaks and muscle activity on steeper ramp transitions. These findings support our previous interpretation that individuals use estimations of ramp angle, not plateau height, to determine their transition strategies.
Jinger S. Gottschall, Bryce Hastings, and Zachary Becker
Popular topics for upper-body resistance training involve the differences between hand positions, open versus closed chain exercises, and movement variations for the novice to the advanced. It was hypothesized that there will be no difference between closed (push-up) versus open (bench press) chain exercises for the primary muscle group activity nor would there be a difference between push-ups on the toes versus knees with respect to the percent contribution of each muscle. Surface muscle activity was measured for 8 upper-body and core muscles during a sequence of push-up and bench press variations with a normalized weight for 12 active men. Each participant completed push-ups and bench press exercises at each of 3 hand positions. The results demonstrated that there were few differences between closed versus open chain exercises for the primary muscle groups with the exception of core activation. In addition, in general, narrow hand positions yielded greater activation, and there were no significant differences between push-ups on the toes versus knees with respect to the percent contribution for the primary muscle groups. In conclusion, closed chain exercises may be preferred for functional training, and knee push-ups may be ideal as a novice push-up variation.
Jinger S. Gottschall, Dmitri Y. Okorokov, Noriaki Okita, and Keith A. Stern
Healthy young adults transition between level and hill surfaces of various angles while walking at fluctuating speeds. These surface transitions have the potential to decrease dynamic balance in both the anterior-posterior and medial-lateral directions. Hence, the purpose of the current study was to analyze modifications in temporal-spatial parameters during hill walking transitions. We hypothesized that in comparison with level walking, the transition strides would indicate the adoption of a distinct gait strategy with a greater base of support. Thirty-four participants completed level and hill trials on a walkway with a 15-degree portable ramp apparatus. We collected data during 4 transition strides between level and ramp surfaces. In support of our hypothesis, compared with level walking, the base of support was 20% greater during 3 out of the 4 transition strides. In short, our results illustrate that healthy young adults did adopt a distinct gait strategy different from both level and hill walking during transitions strides.
Jinger S. Gottschall, Joshua J. Davis, Bryce Hastings, and Heather J. Porter
The growing prevalence and popularity of interval training necessitate additional guidelines in regard to maximal levels of time and intensity. Purpose: To correlate salivary hormones and time in varying heart-rate (HR) zones. The hypothesis was that chronic exercise durations >9% of total exercise time in the >90% maximum HR zone would lead to decreased variation in salivary cortisol concentration after exercise in a 2-bout high-intensity protocol compared with less or more time in this zone. Methods: A total of 35 healthy adults who regularly exercised for an average of 8 hours per week recorded their HR during every training session for 3 weeks. Later, they completed an experimental day composed of two 30-minute high-intensity interval sessions separated by 4 hours of nonactive recovery. The authors collected saliva samples before, immediately following, and 30 minutes after each exercise session to assess changes in cortisol concentrations. Results: There was a correlation between weekly time training at an intensity >90% maximum HR and the variables associated with overtraining. Salivary cortisol concentration fluctuated less in the participants who exercised in this extreme zone for >40 minutes per week (P < .001). Conclusion: Based on the current study data, for individuals who regularly exercise, 4% to 9% total training time above 90% maximum HR is the ideal duration to maximize fitness and minimize symptoms related to overreaching.