• The effect of 17-B estradiol therapy on bone mineral density and structure of alveolar bone in the ovariectomized rat model of postmenopausal osteoporosis

      Johnston, Bryan; Applied Health Sciences Program (Brock University, 2015-01-23)
      The ovariectomized (OVX) rat, a preclinical model for studying postmenopausal bone loss, may also be used to study differences in alveolar bone (AB). The objectives of this study were to quantify the differences in AB following estrogen replacement therapy (ERT), and to investigate the relationship between AB structure and density, and trabecular bone at the femoral neck (FN) and third lumbar vertebral body (LB3). Estrogen treated rats had a higher bone volume fraction (BV/TV) at the AB region (9.8% P < 0.0001), FN (12% P < 0.0001), and LB3 (11.5% P < 0.0001) compared to the OVX group. BV/TV of the AB was positively correlated with the BV/TV at the FN (r = 0.69 P < 0.0001) and the LB3 (r = 0.75 P < 0.0001). The trabecular number (Tb.N), trabecular separation (Tb.Sp), and structure model index (SMI) were also positively correlated (P < 0.05) between the AB and FN (r = 0.42, 0.49, and 0.73, respectfully) and between the AB and LB3 (r = 0.44, 0.63, and 0.69, respectfully). Given the capacity of AB to respond to ERT, future preclinical drug/nutritional intervention studies aimed at improving skeletal health should include the AB as a region of interest (ROI).
    • Effect of a high fat maternal diet on body composition and bone development in male offspring

      Miotto, Paula; Applied Health Sciences Program (Brock University, 2014-08-29)
      Direct high fat (HF) feeding has adverse effects on body composition and bone development in rodents. However, it is unclear whether maternal HF feeding has similar effects in male rat offspring. The objectives of this thesis were to determine if maternal HF feeding altered body composition, plasma hormones, bone development, and bone fatty acid composition in male offspring at weaning and 3 months of age. Maternal HF feeding increased bone mass and altered femur fatty acid composition at weaning, without differences in fat mass, lean mass, plasma hormones, or bone mass (femur or lumbar vertebrae). However, early differences did not persist at 3 months of age or contribute to lower bone strength – following consumption of a control diet post-weaning. These findings suggest that maternal HF feeding can alter body composition and bone development in weanling male offspring, without long-lasting effects if a healthy control diet is consumed post-weaning.
    • The effect of a segmental, localized lower limb cooling protocol on muscular strength and balance

      Montgomery, Roger Edward; Applied Health Sciences Program (Brock University, 2012-11-27)
      The human neuromuscular system is susceptible to changes within the thermal environment. Cold extrinsic temperatures can significantly reduce muscle and nervous system function and communication, which can have consequences for motor performance. A repeated measures design protocol exposed participants to a 12°C cold water immersion (CWI) up to the ankle, knee, and hip to determine the effect that reduced skin and muscle temperature had on balance and strength task execution. Although a linear reduction in the ability to perform balance tasks was seen from the control condition through to the hip CWI, results from the study indicated a significant reduction in dynamic balance (Star Excursion Balance Test reach distance) performance from only the hip CWI (P<0.05). This reduced performance could have been due to an increase in joint stiffness, increased agonist-antagonist co-contraction, and/or reduced isokinetic muscular strength. Reduced physical performance due to cold temperature could negatively impact outdoor recreational athletics.
    • The Effect of a Stickhandling and Puck Control (SPC) Training Intervention on SPC Skills and Wrist Shot Performance Variables in Female Collegiate Ice Hockey Players

      Komenda, Briar; Applied Health Sciences Program (Brock University, 2011-04-11)
      The purpose of the study was to investigate the effect of a 16 session stickhandling and puck control (SPC) off-ice training intervention on SPC skills and wrist shot performance variables. Eighteen female collegiate ice hockey players participated in a crossover design training intervention, whereby players were randomly assigned to two groups. Each group completed 16 SPC training sessions in two conditions [normal vision (NV) and restricted vision (RV)]. Measures obtained after the training intervention revealed significant improvements in SPC skills and wrist shot accuracy. Order of training condition did not reach significance, meaning that SPC improvement occurred as a result of total training volume as opposed to order of training condition. However, overall changes in the RV-NV condition revealed consistently higher effect sizes, meaning a greater improvement in performance. Therefore, support can be provided for this technical approach to SPC training and an alternative method of challenging SPC skills.
    • The effect of a weighted-vest strength and balance training program on obstructed walking in postmenopausal women

      Slack, Jill Patricia.; Applied Health Sciences Program (Brock University, 2003-05-21)
      SUMMARY Background: Age related declines in lower extremity strength have been associated with impaired mobility and changes in gait patterns, which increase the likelihood of falls. Since community dwelling adults encounter a wide range of locomotor challenges including uneven and obstmcted walking surfaces, we examined the effect of a strength 11 and balance exercise program on obstructed walking in postmenopausal women. Objectives: This study examined the effect of a weighted-vest strength and balance exercise program on adaptations of the stance leg during obstacle walking in postmenopausal women. Methods: Eighteen women aged 44-62 years who had not engaged in regular resistance training for the past year were recruited from the St. Catharines community to participate in this study. Eleven women volunteered for an aerobic (walking), strength, and balance training program 3 times per week for 12 weeks while 7 women volunteered as controls. Measurements included: force platform dynamic balance measure of the center of pressure (COP) and ground reaction forces (GRFs) in the stance leg while going over obstacles of different heights (0,5, 10,25 and 30 cm); and isokinetic strength measures of knee and ankle extension and flexion. Results: Of the 18 women, who began the trial, 16 completed it. The EX group showed a significant increase of 40% in ankle plantar flexion strength (P < 0.05). However, no improvements in measures of COP or GRFs were observed for either group. Failure to detect any changes in measures of dynamic balance may be due to small sample size. Conclusions: Postmenopausal women experience significant improvements in ankle strength with 12 weeks of a weighted-vest balance and strength training program, however, these changes do not seem to be associated with any improvement in measures of dynamic balance.
    • The effect of acute low-load resistance exercise with the addition of blood flow occlusion on muscle function in children and adults

      Bax, Alyssa; Applied Health Sciences Program
      Background: Resistance training recommendations to increase muscular strength suggest using high loads. However, some individuals cannot withstand high mechanical stress. Thus, in adults, low-load training is used with blood flow occlusion (BFO), to mimic strength increases from high-load training. Due to differing physiological responses to exercise, children may respond differently to BFO than adults. This study compares the effect of low-load exercise with BFO on maximal voluntary contraction (MVC) and electromyographical (EMG) activity in children and adults. Methods: 16 men (24.4±2.5y) and 14 boys (10.7±2.0y) performed two experimental conditions: (1) occlusion and (2) control. During the occlusion condition, a blood pressure cuff on the upper arm was inflated above systolic pressure during 25 wrist flexions at 35% MVC. Participants then performed an MVC and rated their perceived exertion (RPE). The control condition was the same as the occlusion condition but without the use of BFO. EMG signal was recorded from the flexor carpi radialis (FCR). Results: Men displayed a 16.9±7.1% increase in FCR EMG amplitude across the occlusion (p=0.005) but not the control condition (p=0.919). The boys did not show a change in EMG amplitude between time points (p=0.576) or conditions (p=0.549). Across both age groups, EMG mean power frequency was influenced by a condition-x-time interaction, with a larger decrease across the occlusion (-20.1±9.6%; p<0.001) than the control condition (-5.6±9.7%; p=0.002). Furthermore, across both age groups, MVC torque decreased more following the occlusion (-18.7±12.8%; p<0.001) than the control condition (-6.7±12.5%; p<0.001). Discussion: Based on our findings, a partial explanation for increases in EMG amplitude in the men but not the boys may be that the men recruited more of their higher-threshold motor units than the boys. However, not all measures were consistent in showing child-adult differences, as BFO caused similar decreases in MPF for both groups. Thus, while adults use low-loads with BFO to simulate high-load training, it remains unclear whether this form of training would be as effective for children.
    • Effect of altering dietary calcium and vitamin D in AIN93G diet on bone development in CD-1 male mice

      Wakefield, Brent; Applied Health Sciences Program
      The current levels of vitamin D (vit D) and calcium (Ca) in the AIN93G diet may be higher than required to support healthy bone structure and bone mineral density (BMD) in rodent models. The study objectives were to determine if lower levels of vit D (400 and 100 IU/kg) and Ca (0.35, 0.3, or 0.25%) support healthy bone structure and BMD while maintaining intestinal integrity in weanling male CD-1 mice up to 4 months of age. Lowering the levels of vit D (400 IU/kg) and Ca (0.35%) had no effect on bone structure and BMD, and fecal albumin levels were not different among groups, however, differences were observed in measures of serum LPS among groups. Adjusting the level of vit D to 400 IU/kg and Ca to 0.35% may provide sufficient levels for healthy bone structure and BMD, however further analysis of intestinal integrity is required.
    • The effect of an eight session skate treadmill and agility training program on the degree of separation in ice hockey players

      Harriss, Daniel J.; Applied Health Sciences Program (Brock University, 2011-05-17)
      The sport of ice hockey places multiple simultaneous demands on the physiological, mechanical, and cognitive abilities of individual players. The purpose of the study was to investigate the effect of an eight session degree of separation (DOS) training intervention on sport specific measures of skating, stick handling and puck control movements in competitive ice hockey players. All participants completed a battery of pre and pos t skill and DOS specific tests designed to evaluate DOS abilities: Ttest of agility, a modified Cunningham Faulkner test of anaerobic capacity performed on a skate treadmill and a DOS skate treadmill test. Statistically significant differences were found between groups on the post test scores, meaning that the training intervention had a specific effect on the post test scores of the experimental group (p~O.05). Results of this investigation suggested that a DOS specific training program has the potential to enhance the integration and automation of or sequencing and coordination of uncoordinated ice hockey movements.
    • The effect of an exercise and balance training intervention program on balance and mobility in community-dwelling older adults

      Accardo, Peter; Applied Health Sciences Program
      This thesis investigated the effect of a 12-week exercise and balance training intervention program on perceived and actual balance and mobility outcomes in healthy community-dwelling older adults. Forty-six older adults completed baseline testing including balance confidence and movement reinvestment questionnaires, and a series of balance and mobility tests. Those older adults who were randomly assigned to the intervention group participated in a 12-week program that included aerobic exercise, upper and lower body resistance training, flexibility training and balance training while those assigned to the control group were asked not to make any lifestyle changes during a 12-week control period. The same testing protocol was repeated upon completion of the 12-week intervention program or control period. The results indicated that the intervention group showed improved performance between baseline and 12-week testing sessions for two balance measures (e.g., faster Timed-Up and Go duration, fewer obstacle course errors) while there was no change observed in these measures in the control group. There was also a trend observed for higher balance confidence and less movement self-consciousness reinvestment at the 12-week compared to baseline testing session for the intervention group while no change in these measures was observed in the control group. The findings suggest that participating in 12 weeks of an exercise and balance training intervention can effect change in select perceived and actual balance outcome measures in healthy community-dwelling older adults.
    • The Effect of Blade Alignment on Kinetic and Kinematic Characteristics During the Execution of Goaltender-Specific Movement Patterns

      Dunne, Colin; Applied Health Sciences Program
      The goaltender skate traditionally consists of the boot, cowling, and blade runner. The cowling protects the foot and positions the blade on the boot. Innovations in boot design and material properties have deemed the cowling redundant, presenting the opportunity to manipulate skate blade alignment and potentially reveal a performance advantage. The purpose of the study was to investigate the effect of blade alignment on select kinetic and kinematic variables during the execution of two goaltender-specific movement patterns; Butterfly Drop to Recovery, Lateral Butterfly Slide to Recovery. A male goaltender (n = 1) with professional hockey experience completed an A-B-A, quasi-experimental design across three days investigating four blade alignment conditions. Blade alignment conditions were defined by the blade holder type and positioning on the boot [alignment neutral cowling (ANC), alignment neutral (AN), alignment lateral (AL), and alignment medial (AM)]. Five trials were executed per blade alignment condition for both movements (n=30 trials per day, n=90 trials overall). All trials were executed in a controlled laboratory environment on synthetic ice (xHockeyProductsTM). Kinetic measures included; in-skate peak plantar pressure [PPP(psi)], time to peak plantar pressure [TPP(s)] collected with in-skate LogRTM insoles (Orpyx® Medical Technologies Inc.). Kinematic measures included; butterfly drop velocity [BDV(m/s)], left leg recovery velocity [LLRV(m/s)], right leg recovery velocity [RLRV(m/s)], lateral butterfly slide velocity [LBSV(m/s)], butterfly width [BW(m)] collected with 3D motion capture (ViconTM). Results revealed no significant differences in nineteen of twenty kinetic and kinematic analyses between the two neutral alignment conditions (ANC, AN) defined by different holder types. True Hockey blade holders were retrofit with slots to facilitate the blade alignments. Results revealed significantly higher Butterfly Drop PPP on the AM compared to AN, and higher Left and Right Leg Recovery PPP on AM compared to AL and AN during the Butterfly Drop to Recovery. Results also revealed significantly higher BDV on AM compared to AL and AN during the Butterfly Drop to Recovery, and higher BDV on AM compared to AN during the Lateral Butterfly Slide to Recovery. Study outcomes provide insight into the contribution of manipulating blade alignment to positively impact the execution of goaltender-specific movement patterns.
    • The effect of cardiolipin acyl chain composition on cytochrome c protein conformation and resulting peroxidase activity: Exploring the potential mechanisms that contribute to cellular apoptosis.

      Wilkinson, Jennifer; Applied Health Sciences Program
      Skeletal muscle is a highly active tissue comprising up to 40% of total body weight. This highly dynamic tissue relies on mitochondria for calcium homeostasis, program cell death, and ATP production through mitochondrial respiration. The composition of mitochondrial phospholipids influences the functional efficiency of mitochondrial proteins, and healthy membranes include unsaturated acyl chains to promote respiration. Increasing membrane saturation has been implicated in muscle wasting, a condition caused by apoptosis and identified by the release of specific proteins from the mitochondria. It is unclear how membrane composition promotes the release of these pro-apoptotic proteins, specifically cytochrome c, to induce apoptosis. Thus, in this work synthetic membranes mimicking the composition of mitochondrial membranes from healthy and dystrophic mouse muscle were used. Cytochrome c conformation and function was measured with and without these membranes. There were no differences in protein conformation or function between the healthy and dystrophic membrane mimetics. However, cytochrome c affinity to these membranes was increased with greater unsaturation. This suggests that decreasing membrane saturation, as implicated in muscle wasting diseases, promotes the release of cytochrome c and apoptotic-mediated cell death. As such, interventions to improve or maintain membrane unsaturation may prove to be an alternative therapy for muscle wasting diseases.
    • The effect of elevated muscle fluid volume on indices of muscle damage following an acute bout of eccentric exercise

      Harrison, Rosemarie C.; Applied Health Sciences Program (Brock University, 2008-06-15)
      The primary purpose of the current investigation was to develop an elevated muscle fluid level using a human in-vivo model. The secondary purpose was to determine if an increased muscle fluid content could alter the acute muscle damage response following a bout of eccentric exercise. Eight healthy, recreationally active males participated in a cross-over design involving two randomly assigned trials. A hydration trial (HYD) consisting of a two hour infusion of a hypotonic (0.45%) saline at a rate of 20mL/minVl .73m"^ and a control trial (CON), separated by four weeks. Following the infusion (HYD) or rest period (CON), participants completed a single leg isokinetic eccentric exercise protocol of the quadriceps, consisting of 10 sets of 10 repetitions with a one minute rest between each set. Muscle biopsies were collected prior to the exercise, immediately following and at three hours post exercise. Muscle analysis included determination of wet-dry ratios and quantification of muscle damage using toluidine blue staining and light microscopy. Blood samples were collected prior to, immediately post, three and 24 hours post exercise to determine changes in creatine kinase (CK), lactate dehydrogenase (LD), interleukin-6 (IL-6) and Creactive protein (CRP) levels. Results demonstrated an increased muscle fluid volume in the HYD condition following the infusion when compared to the CON condition. Isometric peak torque was significantly reduced following the exercise in both the HYD and CON conditions. There were no significant differences in the number of areas of muscle damage at any of the time points in either condition, with no differences between conditions. CK levels were significantly greater 24hour post exercise compared to pre, immediately and three hours post similarly in both conditions. LD in the HYD condition followed a similar trend as CK with 24 hour levels higher than pre, immediately post and three hours post and LD levels were significantly greater 24 hours post compared to pre levels in the CON condition, with no differences between conditions. A significant main effect for time was observed for CRP (p<0.05) for time, such that CRP levels increased consistently at each subsequent time point. However, CRP and IL-6 levels were not different at any of the measured time points when comparing the two conditions. Although the current investigation was able to successfully increase muscle fluid volume and an increased CK, LD and CRP were observed, no muscle damage was observed following the eccentric exercise protocol in the CON or HYD conditions. Therefore, the hypotonic infusion used in the HYD condition proved to be a viable method to acutely increase muscle fluid content in in-vivo human skeletal muscle.
    • The effect of extracellular osmolality on cell volume and resting skeletal muscle metabolism

      Antolic, AnaMaria.; Applied Health Sciences Program (Brock University, 2006-06-29)
      The purpose of the current investigation was to establish an in-l'itro skeletal muscle model to study acute alterations in resting skeletal muscle cell volume. Isolated. whole muscle (SOL and EDL) was dissected from Long Evans rats and incubated for 60 min in Sigma Medium-199 (resting tension (lg). bubbled with 95:5% 02:C02, 30 ± 2°C, and pH 7.4). Media osmolality was altered to simulate hypo-osmotic (190 ± 10 Osm) (HYPO) or hyper-osmotic conditions (400 ± 10 Osm) (HYPER) while an iso-osmotic condition (290± 1 0 Osm) (CON) served as a control (n= 17.19.17). Following incubation, relative muscle water content decreased with HYPER and increased with HYPO in both muscle types (p<0.05). The cross-sectional area of HYPO SOL type I and type II fibres increased (p<0.05) while the EDL type 11 fibre area decreased in HYPER and increascd from HYPO exposure. Furthermore, HYPER exposure in both muscles lead to decreased ATP and phosphocreatine (p<0.05) and increased creatine and lactate (p<0.05) compared to CON. This isolated skeletal muscle model proved viable and demonstrated that altering extracellular osmolality could cause acutc alterations in muscle water content and resting muscle metabolism.
    • The Effect of Functional Electrically Stimulated Ambulation Training on Locomotor Function and Quality of Life in Individuals With Incomplete Spinal Cord Injury

      Sharif, Hisham; Applied Health Sciences Program (Brock University, 2012-10-19)
      The purpose of this study was to investigate the effects of a 12-week FES-ambulation program on locomotor function and quality of life after incomplete spinal cord injury. Six individuals with incomplete SCI participated in the study. Over-ground walking endurance (6MWT), speed (10MWT), independence (WISCI II) and body-weight support were assessed. Quality of life was assessed via the SF-36, WHOQOL-BREF, Perceived Stress Scale, Center of Epidemiological Studies for Depression scale, and task self-efficacy. Participants experienced significant improvements in walking endurance (223.6±141.5m to 297.3±164.5m; p=0.03), body-weight support (55.3±12.6% to 14.7±23.2%; p= 0.005) and four of the six participants showed improvements on the WISCI II scale (1-4 points). In addition, there was a significant reduction in reported bodily pain (6.5±1.2 to 5.0±1.7; p=0.04). Therefore, FES-ambulation is an effective means for enhancing over-ground locomotor function in individuals with incomplete SCI. It may also be an effective method for reducing pain in individuals with SCI.
    • THE EFFECT OF GROUP SIZE ON SYNCHRONY AND THE SYNCHRONY EFFECT

      Lewis, Zachary,R.; Applied Health Sciences Program
      Synchronization of behaviour has repeatedly shown to increase endorphin activity as measured by pain threshold (Cohen, Ejsmond-Frey, Knight, & Dunbar, 2010; Sullivan & Rickers, 2014). Although research on synchronous behaviour and the synchrony effect has noted instances of the synchrony effect in multiple physical activities (Cohen et al., 2010; Davis, Taylor, Cohen & Mesoudi, 2015; Kokal, Engel & Kirschner, 2011), it has only incorporated small group trials. Additionally no previous literature has investigated endorphin level subsequent to the immediate termination of exercise. The current study examined the effect of group size on the magnitude of the synchrony effect and explore the length of time the synchrony effect lasts. Thirty-three participants rowed 3 twenty minute time trials on a Concept II ergometer under three counterbalanced conditions - alone, paired and large group (n=12). Pain threshold, was assessed before, immediately post, 5 minutes post, and 10 minutes post each session. Contrary to previous research, a significant synchrony effect was not observed between the solo and group conditions. A significant positive change in pain threshold was reported at the 10 minute post exercise time point compared to the paired condition. This result suggests a longer lasting synchrony effect in a large group condition and that synchronous movement in large groups allows for individuals to exert themselves longer in such conditions.
    • Effect of increased milk intake combined with endurance exercise training on body composition, blood-lipids and inflammatory markers in overweight young males

      Roberts, Rebekah; Applied Health Sciences Program (Brock University, 2013-11-05)
      Consuming low-fat milk (LFM) after resistance training leads to improvements in body composition. Habitual aerobic exercise and dairy intake are relatively easy lifestyle modifications that could benefit a population at risk for becoming obese. Thus, the purpose of this study was to investigate combining increased LFM intake with endurance exercise on body composition, blood-lipid profile and metabolic markers. 40 young males were randomized into four groups: one ingesting 750mL LFM immediately post-exercise, the other 6hrs post-exercise; and two isocaloric carbohydrate groups ingesting at the two different times. Participants completed a 12 week endurance-training program (cycling 1 hour/day at ~60%VO2peak, 5 days/week). 23 participants completed the study. Increases in lean mass (p < 0.05), and decreases in anti-inflammatory marker adiponectin (p < 0.05) were seen in all groups. No other significant changes were observed. Future analyses should focus on longer duration exercise and include a larger sample.
    • The Effect of Maximal Strength Training versus Maximal Strength and Electrostimulation Training on Lower Body Strength, Sprinting Time, and Skating Times

      Bendus, Victoria; Applied Health Sciences Program
      The purpose of the study was to compare and contrast the effectiveness of a traditional maximal strength (MS) training protocol with a maximal strength and electrostimulation (MSES) training regimen on lower body strength, sprinting time, and on ice skating times. Fifteen male (21.5 ± 1.5 years) and 13 female (18.5 ± 3.3 years) competitive ice hockey players were recruited from Midget AA, Junior B, Senior A, and collegiate teams. Participants were stratified by sex and randomized into two groups prior to completing a crossover training study consisting of two 4-week, 8-session training interventions: MS/MSES and MSES/MS. On and off ice assessment batteries were performed at three time points: Pre, Post 1 (week 4), and Post 2 (week 8). Lower body strength was assessed using vertical jump (VJ; cm), horizontal jump (HJ; cm), and one repetition maximum deadlift (DL; kg) and front squat (FS; kg) measures. Sprinting time was assessed using a 20-m sprint (s) and skating times were assessed using five skating drills measuring two-step acceleration and total times (s). Primary 2 (sequence) x 3 (time; Pre, Post 1, Post 2) repeated measures analyses of variance (RM-ANOVA) were conducted to determine if significant differences existed between training sequences (p<.05). Secondary 2 (sequence) x 2 (time; Pre, Post 1) RM-ANOVAs were conducted to determine if significant differences existed between MS and MSES interventions at Post 1. Significant 2 x 3 interactions were revealed for the VJ and stop/start left drill, however no significant differences were evident between sequences at Post 1 or Post 2. Significant main effects of time (groups collapsed) were revealed for the HJ, DL, FS, and combination drill that indicated significant improvement from Pre to Post 2. Significant 2 x 2 interactions were revealed for the VJ, FS, and stop/start right drill, however there were no significant differences between sequences at Post 1. Two of the seventeen variables assessed revealed significant differences between training sequences and four were significantly different between MS and MSES at Post 1. Five RM’s confirmed that significant improvements were demonstrated in strength over 8 weeks of training, however strength increases did not transfer to improvements in sprint or skating times.
    • The effect of perturbation warning on attention switching abilities during dual-task performance in young and older adults

      Hamilton, Lauren; Applied Health Sciences Program (Brock University, 2013-09-26)
      This study examined whether providing an auditory warning would facilitate attention switching abilities in older adults during dual-tasking. Fifteen young and 16 older adults performed a tracking task while recovering their balance from a support surface translation. For half of the trials, an auditory warning was presented to inform participants of the upcoming translation. Performance was quantified through electromyographic (EMG) recordings of the lower limb muscles, while the ability to switch attention between tasks was determined by tracking task error. Providing warning of an upcoming loss of balance resulted in both young and older adults increasing their leg EMG activity by 10-165% (p<0.05) in preparation for the upcoming translation. However, no differences in the timing of attention switching were observed with or without the warning (p=0.424). Together, these findings suggest that providing a perturbation warning has minimal benefits in improving attention switching abilities for balance recovery in healthy older adults.
    • The effect of plyometric exercise on bone turnover markers and osteokines in younger and older women

      Nelson, Katlynne; Applied Health Sciences Program
      The effect of a single-bout of plyometric exercise on markers of bone turnover and Wnt signalling-related osteokines was studied in 20 younger, pre-menopausal women (23.142.33 years) and 20 older, post-menopausal women (57.904.35 years of age). Blood samples were obtained at rest (i.e., pre-exercise) and 5 min, 1h, and 24h post- exercise and were analyzed for C-terminal crosslinking telopeptides of type I collagen (CTX), osteoprotegerin (OPG), sclerostin and dickkopf-1 (DKK-1), and estradiol. Resting levels of CTX, OPG, and sclerostin were significantly higher while DKK-1 and estradiol were significantly lower in older compared to younger women. CTX was higher at 5 min post-exercise compared to pre-exercise in younger women (326.027.0 vs. 292.029.0 pg/mL; p=0.049); however, no response was seen in older women. Sclerostin significantly decreased from 5 min (319.934.6 pg/mL) to 1h post-exercise (245.329.5 pg/mL) but increased between 1h and 24h post-exercise (368.333.9 pg/mL) only in younger women. DKK-1 decreased in both groups. In younger women, the decrease was continuous from 5 min (2560.20120.65 pg/mL) to 24h post-exercise (2176.60115.29 pg/mL, p=0.006). In post-menopausal women, the decrease was between pre-exercise (1949.69177.95 pg/mL) and 1h post-exercise (1549.82187.11 pg/mL, p=0.001) but returning to near pre-exercise levels 24h post-exercise. In the older women, OPG also decreased from pre-exercise (535.8  36.8 pg/mL) to 5 min post-exercise (475.1 39.0 pg/mL; p=0.048) and remained lower than baseline for up to 24h post-exercise (505.032.4 pg/mL; p=0.046). No changes were seen in the younger women. These results suggest that in women, one session of plyometric exercise is sufficient to induce significant changes in bone turnover and Wnt signalling related osteokines, however, the timing of the response varies significantly between age groups.
    • The effect of postural threat on the scaling of anticipatory postural adjustments in healthy young adults

      Phanthanourak, Angel; Applied Health Sciences Program
      Earlier and larger anticipatory postural adjustments (APAs) are generated with increasingly destabilizing movements, such as pulling more forcefully onto a handle, to prevent a loss of balance. The purpose of this study was to determine the influence of postural threat on the ability to scale the magnitude and timing of APAs to increasing amounts of force exertion. Nineteen participants (7 F, 24 ± 2 y, 69.6 ± 9.9 kg, 1.7 ± 0.1 m) pulled on a handle while standing on a surface that was either stationary (No Threat) or that could translate in the medio-lateral direction (Threat). For both conditions, participants completed 36 handle pulls that ranged between 50% and 100% of the participant’s maximal force exertion. For each handle pull trial, APAs were quantified from center of pressure (COP) recordings and electromyographic (EMG) activity of the posterior leg muscles. Results indicated that participants were more physiologically aroused (p=0.013), anxious (p<0.001), and fearful of falling (p<0.001) during the Threat compared to No Threat condition. This threat response was associated with a reduced ability for participants to scale the magnitude of APAs to the amount of force exertion. This was evidenced by 22% shallower regression lines between COP displacement at pulling onset and force exertion during the Threat compared to the No Threat condition (p=0.019). The scaling of APA timing was affected by threat to a lesser extent, as only the regression lines between medial gastrocnemius EMG onset and force exertion were shallower (37%) during the Threat compared to the No Threat condition (p=0.049). Regression lines for COP onset and all other posterior leg EMG amplitudes and onsets to force exertion were not different between conditions. These findings suggest that increased anxiety and fear of falling may contribute to the declines in APA scaling demonstrated by individuals at an increased fall risk (e.g., older adults).