Eadric Bressel

Effect of instruction, surface stability, and load intensity on trunk muscle activity

The aim of this study was to assess the effect of verbal instruction, surface stability, and load intensity on trunk muscle activity levels during the free weight squat exercise. Twelve trained males performed a free weight squat under four conditions: (1) standing on stable ground lifting 50% of their 1-repetition maximum (RM), (2) standing on a BOSU balance trainer lifting 50% of their 1-RM, (3) standing on stable ground lifting 75% of their 1-RM, and (4) receiving verbal instructions to activate the trunk muscles followed by lifting 50% of their 1-RM. Surface EMG activity from muscles rectus abdominis (RA), external oblique (EO), transversus abdominis/internal oblique (TA/IO), and erector spinae (ES) were recorded for each condition and normalized for comparisons. Muscles RA, EO, and TA/IO displayed greater peak activity (39-167%) during squats with instructions compared to the other squat conditions (P=0.04-0.007). Peak EMG activity of muscle ES was greater for the 75% 1-RM condition than squats with instructions or lifting 50% of 1-RM (P=0.04-0.02). The results indicate that if the goal is to enhance EMG activity of the abdominal muscles during a multi-joint squat exercise then verbal instructions may be more effective than increasing load intensity or lifting on an unstable surface. However, in light of other research, conscious co-activation of the trunk muscles during the squat exercise may lead to spinal instability and hazardous compression forces in the lumbar spine.

Trunk muscle activity during exercises performed on land and in water.

PURPOSE The studys purpose was to determine whether trunk muscle activity levels are different during spine stability exercises performed in water compared with on land. METHODS Eleven male participants performed four abdominal trunk exercises on land and in water at the depth of the xiphoid. The exercises were abdominal hollowing, abdominal bracing, and anteroposterior and mediolateral pelvic tilts. During the exercises, surface EMG activity of muscles rectus abdominis (RA), external oblique, lower abdominals, multifidus, and erector spinae (ES) were recorded. EMG data were normalized to a maximal voluntary contraction (MVC), and the subsequent percentage of activity was compared between environments (water and land) with paired t-tests. RESULTS Normalized EMG values for muscles RA, external oblique, lower abdominals, multifidus, and ES were significantly greater for all exercises performed on land than in water (P = 0.026-0.001, effect sizes = 0.52-1.61). The only exception was for mediolateral pelvic tilts where muscle ES values were not different between environments (P = 0.098). CONCLUSIONS When healthy adults perform abdominal hollowing, abdominal bracing, and pelvic tilt exercises in water, most trunk muscles display substantially lower EMG activity when compared with performing the same exercises on land (e.g., abdominal bracing for RA = 20% MVC for land and 10% MVC for water). It is possible that with hydrostatic pressure and buoyancy, trunk muscles play less of a stabilizing role in the aquatic environment, which minimizes their EMG activity levels. Regardless of the mechanism, patients with back pain may find it easier to perform trunk muscle exercises in an aquatic environment first then progress to the land environment because EMG activity may be gradually increased.

The effect of handgrip position on upper extremity neuromuscular responses to arm cranking exercise

The purpose of this study was to determine if handgrip position during arm cranking exercise influences the neuromuscular activity of muscles biceps brachii (BB), lateral head of triceps brachii (TB), middle deltoid (DT), infraspinatus (IS) and brachioradialis (BR). Fifteen participants cranked an arm ergometer using three different handgrip positions (supinated, pronated, and neutral). Electromyographic (EMG) data were recorded from the aforementioned muscles, and relative duration of EMG activation and amplitude were quantified for the first and second 180 degrees of crank angle. EMG measures were analyzed with MANOVA and follow-up univariate procedures; alpha was set at 0.01. The relative durations of EMG activation did not differ between handgrip positions. Muscle IS exhibited 36% less amplitude in the supinated versus neutral handgrip position (second half-cycle), and muscle BR displayed 63% greater amplitude across cycles in the neutral versus supinated and pronated handgrip positions. The greater BR activity displayed in the neutral handgrip position may reflect its anatomical advantage as an elbow flexor when the forearm is in neutral position. Muscle IS exhibited less activity in the supinated position and may be clinically relevant if it allows arm cranking to occur without subsequent shoulder pain, which is often the aim of shoulder rehabilitation.

A field-based approach for examining bicycle seat design effects on seat pressure and perceived stability

The purpose of this study was to investigate the effect of various bicycle seat designs on seat pressure and perceived stability in male and female cyclists using a unique field-based methodology. Thirty participants, comprising male and female cyclists, pedaled a bicycle at 118W over a 350m flat course under three different seat conditions: standard seat, a seat with a partial anterior cutout, and a seat with a complete anterior cutout. The pressure between the bicycle seat and perineum of the cyclist was collected with a remote pressure-sensing mat, and perceived stability was assessed using a continuous visual analogue scale. Anterior seat pressure and stability values for the complete cutout seat were significantly lower (p<0.05; 62-101%) than values for the standard and partial cutout designs. These findings were consistent between males and females. Our results would support the contention that the choice of saddle design should not be dictated by interface pressure alone since optimal anterior seat pressure and perceived seat stability appear to be inversely related.

Transmission of whole body vibration in children while standing

BACKGROUND Whole body vibration has recently been used as a therapeutic intervention for the treatment of children with disabling conditions. Researchers of these studies observed encouraging results; however, children may not be capable of attenuating high vibration accelerations to the head because of low mass. The purpose of this study was to determine if children transmit vibration differently than adults while standing on a vibration platform. METHODS The experimental protocol required 11 children and 10 adults to stand on a commercially available vibration platform at progressively greater frequencies (28, 33, and 42 Hz). Transmissibility of vibration to various skeletal landmarks was assessed with a high speed motion analysis system. FINDINGS Transmissibility in children was 42% and 62% greater than adults for the ankle and hip, respectively (P=0.03; effect size=0.84-1.29). The values at the head were not different between groups (P=0.92) and remained 86% and 50% lower than values at the ankle and knee, respectively (effect size=4.75-19.1). INTERPRETATION Transmissibility of whole body vibration while standing is not markedly different between children and adults. In fact, the only differences are the transmissibility to the ankle and hip which are greater in children when the vibration platform is set at 33 Hz. More importantly, transmissibility to the head is not different between groups. These results do not suggest vibration therapy is safe as the biological response of children to acute or chronic acceleration impacts during whole body vibration is unknown.

The influence of ergometer pedaling direction on peak patellofemoral joint forces

OBJECTIVE To compare patellofemoral joint forces during forward pedaling and reverse pedaling on a bicycle ergometer. DESIGN Experimental within-subject design. BACKGROUND Clinicians addressing patellofemoral pain syndrome often strive to achieve quadriceps strength while reducing forces at the patellofemoral joint. Related to this goal, previous research has shown greater activity in the quadriceps during reverse pedaling compared to forward pedaling on a bicycle ergometer, however, patellofemoral joint forces were not examined. METHODS Twenty-one healthy males performed 5-min exercise bouts for forward and reverse pedaling while normal and tangential pedal forces and kinematic data were collected. Inertial properties of each segment were estimated and net joint moments were calculated using Newtonian inverse dynamics. Patellofemoral joint forces (Fpf) were quantified using the equation Fpf = 2FQ . sin beta/2, where FQ is the quadriceps force and beta is the patellar mechanism angle. RESULTS Reverse pedaling exhibited a 110% greater peak patellofemoral joint force and a 149% greater quadriceps force than forward pedaling. Peak effective moment arm lengths were not different between conditions. CONCLUSIONS Reverse pedaling is associated with a greater peak patellofemoral force than forward pedaling. The peak force was influenced by the quadriceps force and not by the moment arm length. RELEVANCE Insufficient data exist concerning the use of reverse pedaling as an alternative to forward pedaling for rehabilitation of knee disorders. Although quadriceps activity appears greater for reverse pedaling compared to forward pedaling, greater peak patellofemoral forces contradict clinical treatment goals for patellofemoral pain syndrome and may lead to load-elicited pain or damage to joint structures.

High-Intensity Interval Training on an Aquatic Treadmill in Adults With Osteoarthritis: Effect on Pain, Balance, Function, and Mobility

Abstract Bressel, E, Wing, JE, Miller, AI, and Dolny, DG. High-intensity interval training on an aquatic treadmill in adults with osteoarthritis: effect on pain, balance, function, and mobility. J Strength Cond Res 28(8): 2088–2096, 2014—Although aquatic exercise is considered a potentially effective treatment intervention for people with osteoarthritis (OA), previous research has focused primarily on calisthenics in a shallow pool with the inherent limitations on regulating exercise intensity. The purpose of this study was to quantify the efficacy of a 6-week aquatic treadmill exercise program on measures of pain, balance, function, and mobility. Eighteen participants (age = 64.5 ± 10.2 years) with knee OA completed a non-exercise control period followed by a 6-week exercise period. Outcome measures included visual analog scales for pain, posturography for balance, sit-to-stand test for function, and a 10-m walk test for mobility. The exercise protocol included balance training and high-intensity interval training (HIT) in an aquatic treadmill using water jets to destabilize while standing and achieve high ratings of perceived exertion (14–19) while walking. In comparison with pretests, participants displayed reduced joint pain (pre = 50.3 ± 24.8 mm vs. post = 15.8 ± 10.6 mm), improved balance (equilibrium pre = 66.6 ± 11.0 vs. post = 73.5 ± 7.1), function (rising index pre = 0.49 ± 0.19% vs. post = 0.33 ± 0.11%), and mobility (walk pre = 8.6 ± 1.4 s vs. post = 7.8 ± 1.1 s) after participating in the exercise protocol (p = 0.03–0.001). The same benefits were not observed after the non-exercise control period. Adherence to the exercise protocol was exceptional and no participants reported adverse effects, suggesting that aquatic treadmill exercise that incorporates balance and HIT training was well tolerated by patients with OA and may be effective at managing symptoms of OA.

Effect of pelvic, hip, and knee position on ankle joint range of motion.

OBJECTIVE To determine if pelvic posture, hip, and knee positions influence range of motion about the ankle joint. STUDY DESIGN Quasi-experimental repeated measures. SETTING Biomechanics laboratory in a university setting. PARTICIPANTS Eleven men and six women free of ankle joint trauma. MAIN OUTCOME MEASURES Range of motion about the ankle joint. RESULTS ANOVA revealed a significant difference for position main effect on ankle joint range of motion (p=0.01). Post-hoc tests revealed that ankle joint range of motion significantly decreased as participants moved from flexion (i.e., 90 degrees hip and 90 degrees knee), to supine, and to long sitting (47.3 degrees , 38.8 degrees , and 16.4 degrees ; p<0.05). No significant differences were revealed for pelvic posture (p=0.64). CONCLUSIONS These findings indicate that pelvic posture may not influence ankle joint range of motion regardless of hip and knee joint positions. However, the combination of hip flexion and knee extension (i.e., long sitting) produces the greatest deficits in ankle joint range of motion.

The Landing Phase of a Jump Strategies to Minimize Injuries

Abstract “What goes up, must come down,” according to the old saying. The problem is that athletes often train for the “going up,” while neglecting the “coming down”—and all its potential for injury.

Predicting a 10 Repetition Maximum for the Free Weight Parallel Squat Using the 45° Angled Leg Press

&NA; Willardson, J.M., and E. Bressel. Predicting a 10 repetition maximum for the free weight parallel squat using the 45° angled leg press. J. Strength Cond. Res. 18(3):567–571. 2004.—The purpose of this research was to devise prediction equations whereby a 10 repetition maximum (10RM) for the free weight parallel squat could be predicted using the following predictor variables: 10RM for the 45° angled leg press, body mass, and limb length. Sixty men were tested over a 3‐week period, with 1 testing session each week. During each testing session, subjects performed a 10RM for the free weight parallel squat and 45° angled leg press. Stepwise multiple regression analysis showed leg press mass lifted to be a significant predictor of squat mass lifted for both the advanced and the novice groups (p < 0.05). Leg press mass lifted accounted for approximately 25% of the variance in squat mass lifted for the novice group and 55% of the variance in squat mass lifted for the advanced group. Limb length and body mass were not significant predictors of squat mass lifted for either group. The following prediction equations were devised: (a) novice group squat mass = leg press mass (0.210) + 36.244 kg, (b) advanced group squat mass = leg press mass (0.310) + 19.438 kg, and (c) subject pool squat mass = leg press mass (0.354) + 2.235 kg. These prediction equations may save time and reduce the risk of injury when switching from the leg press to the squat exercise.