Chris J. Hass

Prescription of resistance training for healthy populations

AbstractAlthough there are well documented protective health benefits conferred by regular physical activity, most individuals of all ages are not physically active at a level for sufficient maintenance of health. Consequently, a major public health goal is to improve the collective health and fitness levels of all individuals. The American College of Sports Medicine (ACSM) and other international organisations have established guidelines for comprehensive exercise programmes composed of aerobic, flexibility and resistance-exercise training. Resistance training is the most effective method available for maintaining and increasing lean body mass and improving muscular strength and endurance.Furthermore, there is an increasing amount of evidence suggesting that resistance training may significantly improve many health factors associated with the prevention of chronic diseases. These health benefits can be safely obtained by most segments of the population when prescribed appropriate resistance-exercise programmes. Resistance-training programmes should be tailored to meet the needs and goals of the individual and should incorporate a variety of exercises performed at a sufficient intensity to enhance the development and maintenance of muscular strength and endurance, and lean body mass. A minimum of 1 set of 8 to 10 exercises (multi-joint and single joint) that involve the major muscle groups should be performed 2 to 3 times a week for healthy participants of all ages. More technical and advanced training including periodised multiple set regimens and/or advanced exercises may be more appropriate for individuals whose goals include maximum gains in strength and lean body mass. However, the existing literature supports the guidelines as outlined in this paper for children and adults of all ages seeking the health and fitness benefits associated with resistance training.

Single versus multiple sets in long-term recreational weightlifters

PURPOSE The purpose of this study was to determine the effects of increasing training volume from one set to three sets on muscular strength, muscular endurance, and body composition in adult recreational weight lifters. METHODS Forty-two adults (age 39.7 +/- 6.2 yr; 6.2 +/- 4.6 yr weight training experience) who had been performing one set using a nine-exercise resistance training circuit (RTC) for a minimum of 1 yr participated in this study. Subjects continued to perform one set (EX-1; N = 21) or performed three sets (EX-3; N = 21) of 8-12 repetitions to muscular failure 3 d x wk(-1) for 13 wk using RTC. One repetition maximums (1-RM) were measured for leg extension (LE), leg curl (LC), chest press (CP), overhead press (OP), and biceps curl (BC). Muscular endurance was evaluated for the CP and LE as the number of repetitions to failure using 75% of pretraining 1-RM. Body composition was estimated using the sum of seven skinfold measures. RESULTS Both groups significantly improved muscular endurance and 1 RM strength (EX-1 by: 13.6% LE; 9.2% LC; 11.9% CP; 8.7% OP; 8.3% BC; and EX-3 by: 12.8% LE; 12.0% LC; 13.5% CP; 12.4% OP; 10.3% BC) (P < 0.05). Both groups significantly improved lean body mass (P < 0.05). No significant differences between groups were found for any of the test variables (P > 0.05). CONCLUSION Both groups significantly improved muscular fitness and body composition as a result of the 13 wk of training. The results show that one-set programs are still effective even after a year of training and that increasing training volume over 13 wk does not lead to significantly greater improvements in fitness for adult recreational weight lifters.

Chronic ankle instability alters central organization of movement.

Background Chronic ankle instability alters spinal level sensorimotor function and is hypothesized to alter supraspinal motor control mechanisms. Gait initiation is a functional task modulated by supraspinal pathways, but the effect of chronic ankle instability, a peripheral musculoskeletal impairment, on gait initiation and thus supraspinal motor control mechanisms remains unknown. Purpose This study was conducted to determine if supraspinal aspects of motor control are altered in subjects with chronic ankle instability. Study Design Controlled laboratory study. Methods Subjects with chronic ankle instability (5 males, 15 females; age, 20.5 ± 1.0 years; height, 169.8 ± 9.8 cm; weight, 74.2 ± 20.2 kg) and uninjured controls (4 males, 16 females; age, 20.85 ± 1.6 years; height, 164.3 ± 7.9 cm; weight, 64.2 ± 10.62 kg) completed 5 gait initiation trials for each leg at a self-selected pace. The resulting trajectory of the center of pressure trace was investigated and peak center of pressure excursions in the anteroposterior and mediolateral directions, peak resultant center of pressure excursions, and average direction-specific velocities were calculated. Results Significant group × limb interactions were noted during the first (resultant center of pressure displacement [F1,37 = 4.60, P = .04]) and second (mediolateral center of pressure displacement [F1,37 = 3.82, P = .05]) period of gait initiation. Center of pressure displacement was reduced (impaired) in the involved limb of the chronic ankle instability group (resultant, 0.29 ± 0.02; mediolateral, 0.72 ± 0.02) relative to the uninvolved limb of the chronic ankle instability group (resultant, 0.32 ± 0.02; mediolateral, 0.76 ± 0.02) and both limbs of the control group (resultant, 0.32 ± 0.02; mediolateral, 0.74 ± 0.02) when the involved limb of the chronic ankle instability group served as the initial stance limb. Conclusion These interactions suggest that supraspinal motor control mechanisms are altered in subjects with chronic ankle instability to place a greater emphasis on reducing the postural demands on the involved limb. Clinical Relevance These changes suggest that supraspinal adaptations to motor control may be an important contributor to the underlying neurophysiologic mechanism of chronic ankle instability. The presence of supraspinal adaptations in subjects with chronic ankle instability also indicates that health care providers and rehabilitation specialists treat chronic ankle instability as a global/central and not just a local/peripheral injury.

Resistance Training With Creatine Monohydrate Improves Upper-Body Strength in Patients With Parkinson Disease: A Randomized Trial

Background. Persons with Parkinson disease (PD) exhibit decreased muscular fitness including decreased muscle mass, muscle strength, bioenergetic capabilities and increased fatigability. Objective. This purpose of this investigation was to evaluate the therapeutic effects of resistance training with and without creatine supplementation in patients with mild to moderate PD. Methods. Twenty patients with idiopathic PD were randomized to receive creatine monohydrate supplementation plus resistance training (CRE) or placebo (lactose monohydrate) plus resistance training (PLA), using a double-blind procedure. Creatine and placebo supplementation consisted of 20 g/d for the first 5 days and 5 g/d thereafter. Both groups participated in progressive resistance training (24 sessions, 2 times per week, 1 set of 8-12 repetitions, 9 exercises). Participants performed 1-repetition maximum (1-RM) for chest press, leg extension, and biceps curl. Muscular endurance was evaluated for chest press and leg extension as the number of repetitions to failure using 60% of baseline 1-RM. Functional performance was evaluated as the time to perform 3 consecutive chair rises. Results. Statistical analyses (ANOVA) revealed significant Group × Time interactions for chest press strength and biceps curl strength, and post hoc testing revealed that the improvement was significantly greater for CRE. Chair rise performance significantly improved only for CRE (12%, P = .03). Both PLA and CRE significantly improved 1-RM for leg extension (PLA: 16%; CRE: 18%). Muscular endurance improved significantly for both groups. Conclusions. These findings demonstrate that creatine supplementation can enhance the benefits of resistance training in patients with PD.

Effect of moderate-intensity exercise training on the cognitive function of young adults with intellectual disabilities.

Abstract Pastula RM, Stopka CB, Delisle AT, and Hass CJ. Effect of moderate-intensity exercise training on the cognitive function of young adults with intellectual disabilities. J Strength Cond Res 26(12): 3441–3448, 2012—In addition to cognitive impairment, young adults with intellectual disabilities (IDs) are also more likely to be in poor health. Exercise may help ameliorate both of these deficits. While the health benefits of exercise are well documented and understood, the cognitive benefits of exercise are emerging. Exercise has been shown to improve the cognitive function of young, old, and diseased populations but few studies have evaluated the effect of exercise training on the cognitive functioning of individuals with IDs. The purpose of this study was to determine the effect of moderate-intensity exercise training on the cognitive function of young adults with IDs. Fourteen students (age, 19.4 ± 1.3 years) with mild to moderate IDs participated in an 8-week comprehensive exercise intervention program based on circuit training, aerobic dancing, and adapted sport activities. Sessions lasted 45 minutes, and intensity was maintained at 60–70% of maximum heart rate (HRmax). Aerobic fitness was assessed via the Young Men’s Christian Association (YMCA) step test, and intellectual functioning was assessed via 3 subtests from the Woodcock-Johnson III Tests of Cognitive Abilities once before and after the intervention. Performance was significantly improved on all 3 cognitive tests (all, p < 0.002). Aerobic fitness also significantly improved (p < 0.002). The mean percent increase in processing speed, a measure taking into account each individuals performance on the 3 subtests, was 103%. The mean individual improvement in aerobic fitness was 17.5%. Moderate-intensity exercise training can yield robust improvements in the cognitive functioning and aerobic fitness of young adults with IDs. These effects support the inclusion of exercise into the lives of young adults with ID to promote their physical and cognitive health. Fourteen students (age, 19.4 ± 1.3 years) with mild to moderate IDs participated in an 8-week comprehensive exercise intervention program based on circuit training, aerobic dancing, and adapted sport activities. Sessions lasted 45 minutes and intensity Powered by Editorial Manager and Preprint Manager from Aries Systems Corporation was maintained at 60–70% of HRmax. Aerobic fitness was assessed via the YMCA step test, and intellectual functioning was assessed via 3 subtests from the Woodcock-Johnson III Tests of Cognitive Abilities once before and after the intervention. Performance was significantly improved on all 3 cognitive tests (all, p < 0.002). Aerobic fitness also significantly improved (p < 0.002). The mean percent increase in processing speed, a measure taking into account each individuals performance on the 3 subtests, was 103%. The mean individual improvement in aerobic fitness was 17.5%. Moderate-intensity exercise training can yield robust improvements in the cognitive functioning and aerobic fitness of young adults with IDs. These effects support the inclusion of exercise into the lives of young adults with ID to promote their physical and cognitive health.

Decreased static and dynamic postural control in children with autism spectrum disorders

The purpose of this study was to investigate postural control in children with Autism Spectrum Disorders (ASD) during static and dynamic postural challenges. We evaluated postural sway during quiet stance and the center of pressure (COP) shift mechanism during gait initiation for 13 children with ASD and 12 age-matched typically developing (TD) children. Children with ASD produced 438% greater normalized mediolateral sway (p<0.05) and 104% greater normalized anteroposterior sway (p<0.05) than TD children. Consequently, normalized sway area was also significantly greater (p<0.05) in the group with ASD. Similarly, the maximum separation between the COP and center of mass (COM) during quiet stance was 100% greater in the anteroposterior direction (p<0.05) and 146% greater in the resultant direction (p<0.05) for children with ASD. No significant difference was observed in the mediolateral direction, in spite of the 123% greater separation detected in children with ASD. During gait initiation, no group differences were detected in the posterior COP shift mechanism, suggesting the mechanism for generating forward momentum is intact. However, significantly smaller lateral COP shifts (p<0.05) were observed in children with ASD, suggesting instability or an alternative strategy for generating momentum in the mediolateral direction. These results help to clarify some discrepancies in the literature, suggesting an impaired or immature control of posture, even under the most basic conditions when no afferent or sensory information have been removed or modified. Additionally, these findings provide new insight into dynamic balance in children with ASD.

Brain penetration effects of microelectrodes and DBS leads in STN or GPi

Objective: To determine how intraoperative microelectrode recordings (MER) and intraoperative lead placement acutely influence tremor, rigidity, and bradykinesia. Secondarily, to evaluate whether the longevity of the MER and lead placement effects were influenced by target location (subthalamic nucleus (STN) or globus pallidus interna (GPi)). Background: Currently most groups who perform deep brain stimulation (DBS) for Parkinson disease (PD) use MER, as well as macrostimulation (test stimulation), to refine DBS lead position. Following MER and/or test stimulation, however, there may be a resultant “collision/implantation” or “microlesion” effect, thought to result from disruption of cells and/or fibres within the penetrated region. These effects have not been carefully quantified. Methods: 47 consecutive patients with PD undergoing unilateral DBS for PD (STN or GPi DBS) were evaluated. Motor function was measured at six time points with a modified motor Unified Parkinson Disease Rating Scale (UPDRS): (1) preoperatively, (2) immediately after MER, (3) immediately after lead implantation/collision, (4) 4 months following surgery—off medications, on DBS (12 h medication washout), (5) 6 months postoperatively—off medication and off DBS (12 h washout) and (6) 6 months—on medication and off DBS (12 h washout). Results: Significant improvements in motor scores (p<0.05) (tremor, rigidity, bradykinesia) were observed as a result of MER and lead placement. The improvements were similar in magnitude to what was observed at 4 and 6 months post-DBS following programming and medication optimisation. When washed out (medications and DBS) for 12 h, UPDRS motor scores were still improved compared with preoperative testing. There was a larger improvement in STN compared with GPi following MER (p<0.05) and a trend for significance following lead placement (p<0.08) but long term outcome was similar. Conclusion: This study demonstrated significant acute intraoperative penetration effects resulting from MER and lead placement/collision in PD. Clinicians rating patients in the operating suite should be aware of these effects, and should consider pre- and post-lead placement rating scales prior to activating DBS. The collision/implantation effects were greater intraoperatively with STN compared with GPi, and with greater disease duration there was a larger effect.

Gait termination control strategies are altered in chronic ankle instability subjects.

UNLABELLED Despite the high incidence of chronic ankle instability (CAI), the underlying neurophysiologic mechanism is unknown. Evidence suggests that both feed-forward and feedback mechanisms may play a role. However, no investigation has examined both control mechanisms during the same movement task in the same cohort of CAI patients. PURPOSE To determine the neuromuscular and biomechanical control alterations present in CAI patients during planned (feed-forward) and unplanned (feedback) gait termination. METHODS Twenty subjects with CAI and 20 uninjured controls completed planned and unplanned gait termination protocols. Both tasks began with subjects walking at a self-selected speed across a 12-m walkway. Unplanned gait termination required subjects to stop during randomly selected trials on two adjacent force plates when cued. Planned gait termination required purposeful stopping on the force places. Propulsive and braking force magnitude and the dynamic postural stability index were calculated from the resulting ground reaction forces. In addition, muscle activity from the soleus, tibialis anterior, and gluteus medius was collected bilaterally. RESULTS Both maximum propulsive (CAI = 99.8 +/- 40.8 N, control = 88.6 +/- 33.6 N) and braking (CAI = 207.1 +/- 80.9 N, control = 161.6 +/- 62.2 N) forces were significantly higher in the CAI group. The dynamic postural stability index revealed higher scores in the CAI group (0.24 +/- 0.03) compared with the control group (0.22 +/- 0.03). Muscle activation of the soleus and tibialis anterior differed during unplanned and planned gait termination between groups (P < 0.05) and between the limbs of the CAI group (P < 0.05). CONCLUSIONS Altered biomechanical strategies during both planned and unplanned gait termination indicate that patients with CAI have alterations in feed-forward neuromuscular control and suggest the presence of feedback neuromuscular control deficits.

Progressive resistance training improves gait initiation in individuals with Parkinson\'s disease

An impaired ability to initiate walking is a common feature of postural instability and gait impairment in Parkinsons disease. While progressive resistance training (PRT) has been proposed to be an effective modality to improve balance and gait function in people with Parkinsons disease, there are a limited number of randomized trials and no studies have evaluated gait initiation performance. Thus, the purpose of this study was to examine the potential benefits PRT on GI performance in people with Parkinsons disease. Eighteen individuals with idiopathic PD were randomly assigned to either a twice weekly PRT program or a non-contact control group for 10 weeks. Biomechanical analysis of GI was performed pre- and post-intervention. Dependent variables of interest included the displacement of the center-of-pressure (COP) during the anticipatory postural phase of GI as well as the initial stride length and velocity. The PRT group demonstrated improvements in the posterior displacement of the COP and the initial stride length and velocity. There were no improvements in any variables for the control subjects. These results suggest that PRT may be an effective non-pharmacological and nonsurgical treatment to improve GI performance in PWP.

Impact forces and neck muscle activity in heading by collegiate female soccer players

Three soccer header types (shooting, clearing and passing) and two heading approaches (standing and jumping) were manipulated to quantify impact forces and neck muscle activity in elite female soccer players. The 15 participants were Division I intercollegiate soccer players. Impact forces were measured by a 15-sensor pressure array secured on the forehead. The electromyographic (EMG) activity of the left and right sternocleidomastoid and trapezius muscles was recorded using surface electrodes. Maximum impact forces and impulses as well as the EMG data were analysed with separate repeated-measures analyses of variance. Impact forces and impulses did not differ among the header types or approaches. Higher values were found for jumping versus standing headers in the mean normalized EMG for the right sternocleidomastoid. In addition, the integrated EMG was greater for the right sternocleidomastoid and right and left trapezius (P < 0.05). The sternocleidomastoid became active earlier than the trapezius and showed greater activity before ball contact. The trapezius became active just before ball contact and showed greater activity after ball contact. The increased muscle activity observed in the neck during the jumping approach appears to stabilize the connection between the head and body, thereby increasing the stability of the head-neck complex.