Instability resistance training for health and performance

Assessment of the Speed and Power of Push-Ups Performed on Surfaces with Different Degrees of Instability

(I) Training in unstable conditions, with different elements, platforms, or situations, has been used because there is a significant increase in muscle activation, balance, proprioception, and even sports performance. However, it is not known how the devices used are classified according to performance variables, nor the differences according to instability experience. (II) This study aims to analyze the differences in power and speed in push-ups with different situations of instability in trained and untrained male subjects. Power and speed in push-up exercise were analyzed in 26 untrained and 25 trained participants in 6 different situations (one stable and five unstable) (1) stable (PS), (2) monopodal (PM), (3) rings (PR), (4) TRX^® (PT), (5) hands-on Bosu^® (PH) (6) feet on Bosu^® (PF). The variables were analyzed using a linear position transducer. (III) The best data were evidenced with PS, followed by PR, PM, PT, PH and PF. The trained subjects obtained better results in all the conditions analyzed in mean and maximum power and speed values (p < 0.001). The decrease in these variables was significantly greater in the untrained subjects than in the trained subjects in the PR situation (8% and 18% respectively). In PF there were differences between groups (p < 0.001), reaching between 32-46% in all variables. The difference between the two groups was notable, varying between 12-58%. (IV) The results showed a negative and progressive influence of instability on power and speed in push-ups. This suggests that instability should be adapted to the subject's experience and is not advisable in untrained subjects who wish to improve power.

Biomechanical analysis of lifting on stable versus unstable surfaces-a laboratory-based proof-of-concept study

Background

Many workers performing manual handling tasks suffer from musculoskeletal disorders (MSD). Previous research has identified several loading aspects associated with manual handling, but it is still unknown if lifting on an unstable surface is associated with increased biomechanical loading of different body parts.

Aim

This proof-of-concept study aims to study what kinematic and kinetic movement parameters, such as movement time, joint angles, torque, and muscle activity are feasible and of importance when studying the effect of lifting on surfaces with varying degrees of stability in an experimental set-up.

Methods

Measurements were taken during three different surface conditions: stable, slightly unstable, and unstable. The participants were instructed to lift a box from the floor and place it on a table in front of them. The weight of the box varied from 0.5 to 15.5 kg. By using a motion capture system (VICON) with 28 reflective markers placed on the participants and one on the box, one Kistler force plate for measuring force levels and center of pressure movements (CoP), and four electromyographic transmitters (EMG), we analyzed the downward and upward phases of the lifting movement, using the Friedman’s test for repeated measures.

Results

Statistically significant results with less joint movements in the lower and upper back were seen with increased instability during both the downward and upward phases. The decrease in trunk movements with increased instability resulted in a somewhat more flexed knee position during the movement, a lower torque in the lower back, and a decrease in CoP movements, but no differences in movement time or muscle activity in back and knee muscles.

Conclusion

Lifting while standing on unstable surfaces resulted in an alteration of both kinematics and kinetics parameters; however, further studies regarding whether this is an additional risk factor for developing lower back pain are needed. Muscle activity levels were not altered due to instability and due to the complexity of the measurement, and we suggest not including EMG measures in future experiments of this type.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-022-01157-2.

No Difference in the Acute Effects of Randomization vs. Blocking of Units of Lower-Extremity Proprioceptive Training on Balance and Postural Control in Young Healthy Male Adults

Random practice is a form of differential learning and its favorable acute effects on motor performance are well described when visual tasks are practiced. However, no study to date has investigated the acute effects of differential learning using variable proprioceptive stimuli instead of the visual cues. The aim of the present study was to compare the acute effects of randomized versus blocked lower-extremity proprioceptive training stimuli on balance and postural adjustments. In two conditions, healthy young males (n = 15, age = 23 years) performed 16 one-legged landings on a board tilted in four directions: 1) tilt direction unknown and randomized and 2) tilt direction known with order of presentation blocked. Multi-segmental angular sway while balancing on an unstable surface and postural responses to perturbation stimulus by surface tilts were measured before and 4 min after training. Overall frontal-plane postural sway on the unstable surface decreased (p < 0.05, η² = 0.022) in both conditions, while sagittal-plane postural sway remained unchanged. When the surface was toes-up tilted in the perturbation test, the sagittal-plane shank-thigh-pelvis alignment improved in both conditions (p < 0.05, η² = 0.017), but the direction of the segmental positioning was non-uniform across participants. We conclude that randomization vs. blocking of units of lower-extremity proprioceptive training did not affect balance and postural control in our cohort of healthy young adults but the improvements were test-specific.

Sensorimotor training prior total knee arthroplasty and effects on functional outcome: A systematic review and meta-analysis

BACKGROUND

Altered muscle activation patterns and proprioception, loss of strength, and weight bearing asymmetries are common limitations after total knee arthroplasty, which can also affect balance. Therefore, preoperative sensorimotor training has been proposed to enhance surgical outcome.

RESEARCH QUESTION

Is preoperative sensorimotor training effective in improving functional outcome in patients undergoing total knee arthroplasty? Does preoperative sensorimotor training affect secondary outcomes such as balance, pain, and quality of life?

METHODS

A systematic review and meta-analysis were conducted by searching PEDro, MEDLINE, Embase, Cochrane Library, and Scopus databases from inception to May 2020. Studies were eligible if participants underwent total knee arthroplasty after two or more weeks of preoperative sensorimotor training. A meta-analysis compared the effects of such interventions with standard care before and after surgery using standardized mean differences (SMD) with 95 % confidence interval (CI). Functional outcome was the primary measure. Balance, pain, and quality of life were also outcomes of interest.

RESULTS

Of the 384 items identified, 7 met the inclusion criteria, and 332 participants were assessed. There was limited evidence suggesting that preoperative sensorimotor training enhanced self-reported function (SMD, 0.89; 95 % CI, 0.16-1.62), functional performance (SMD, 0.56; 95 % CI, 0.19 to 0.93), or knee function (SMD = 0.22-1.05) compared with conventional care. Moderate quality evidence suggested that benefits were only maintained in terms of functional performance up to 3 months after surgery (SMD = 0.37; 95 % CI, 0.13 to 0.62). The outcome was similar after one year.

SIGNIFICANCE

Compared with conventional care, preoperative sensorimotor training may enhance early postoperative functional recovery, with no additional benefits on balance, knee function, or pain. The outcome is the same one year after surgery, regardless of whether such training is implemented. Further investigation is needed to determine whether sensorimotor training may be a feasible conservative treatment for severe knee osteoarthritis.

Stable to unstable differences in force-velocity-power profiling during chest presses and squats

Despite several studies investigating the effect of instability resistance exercises on neuromuscular performance, the force-velocity-power characteristics of muscles involved in lifting tasks and the underlying mechanisms have not been fully explored. This study investigates power-velocity and force-velocity relationships during resistance exercises performed on stable and unstable surfaces with different weights. A group of 63 physically active young men performed chest presses on the bench and Swiss ball, and squats on the firm surface and BOSU ball with weights from 20 kg to at least 85% of one-repetition maximum. Peak and/or mean values of power, velocity and force were analyzed. Results showed significantly lower peak power and force during chest presses on the Swiss ball as opposed to the bench at lower velocities (147.6 W and 176.0 N at 1.1 m·s^-1, 108.7 W and 126.4 N at 1.3 m·s^-1, 112.0 W and 72.7 N at 1.5 m·s^-1; all at p < 0.01). Their values produced at lower velocities were also significantly lower during squats on the BOSU ball when compared to the firm surface (232.2 W and 257.1 N at 1.1 m·s^-1, 228.2 W and 173.3 N at 1.2 m·s^-1, 245.1 W and 156.8 N at 1.3 m·s^-1, 254.5 W and 113.5 N at 1.4 m·s^-1; all at p < 0.05). These significant differences between power produced during stable and unstable resistance exercises at lower velocities (or at higher loads) have to be taken into account in sports that require production of a high force in a short time. Because of the variable loading patterns under unstable conditions, it is necessary to quantify the optimal exercise load for each individual athlete.

Relationship Between Training Factors and Injuries in Stand-Up Paddleboarding Athletes

Stand-up paddleboarding (SUP) is an increasingly popular sport but, as in other sports, there is an injury ratio associated with practicing it. In other types of sport, some factors have been linked to the likelihood of suffering an injury, among which stretching, core training and resistance training may be considered the most significant. Therefore, the main aim of this study was to identify the training factors that could influence injuries suffered by participants in international SUP competitions. Ninety-seven questionnaires were collected from paddlers who participated in an international SUP circuit, with epidemiological data being gathered about injuries and different questions related to the training undertaken. A multi-factor ANOVA test was used to identify the factors which influence the state of injury. Results showed that almost 60% of injuries occurred in the arms or in the upper thoracic region, around 65% of which were in tendons or muscles and, in almost half of cases, were related to overuse. Likewise, the results showed that athletes with injury performed fewer resistance training sessions per week (p = 0.028), over fewer months per year (p = 0.001), more weekly training sessions (p = 0.004) and, lastly, a greater volume of weekly training (p = 0.003) than athletes without injury. Moreover, the most important training factors that reduce the likelihood of suffering an injury were taken into account-in. particular, resistance training alone (p = 0.011) or together with CORE training (p = 0.006) or stretching (p = 0.012), and the dominant side of paddling (p = 0.032). In conclusion, resistance training would seem to reduce the likelihood of injury among SUP practitioners, and such benefits could be obtained by resistance training alone or in combination with CORE training or stretching.

BALANCE TRAINING: DOES ANTICIPATED BALANCE CONFIDENCE CORRELATE WITH ACTUAL BALANCE CONFIDENCE FOR DIFFERENT UNSTABLE OBJECTS?

Background

Sports rehabilitation professionals often prescribe unstable objects for balance training. Unfortunately, there is a lack of measurement of balance confidence when incorporating these objects. Currently, there is no consensus on the optimal balance confidence measure or proposed progression of unstable objects. Understanding the influence of balance confidence on task performance using unstable objects may help professionals better prescribe a balance training program.

Purpose

The primary purpose of this investigation was to explore the correlation between anticipated and actual balance confidence on different unstable objects during static double leg and single leg stance. The secondary purpose was to explore the correlation between anticipated and actual unstable object difficulty rankings.

Study Design

Repeated measure observational, controlled trial.

Methods

Sixty-five active, healthy adults (M = 35, F = 30) (mean age = 24.38 ± 3.56) underwent two testing sessions. During session one, participants took an online survey, rating their anticipated balance confidence after observing images of different unstable objects. During session two, participants stood on each unstable object under two conditions (static double leg stance and single leg stance) and rated their actual balance confidence. The main outcome measure was an ordinal balance confidence score adapted from the activities-specific balance confidence scale. Statistical analysis included subject demographic calculations and appropriate non-parametric tests.

Results

For the double leg stance and single leg stance conditions, there was a very strong correlation between anticipated and actual balance confidence scores on the stable surface (ρ = 1.0, p = <.001). There was a weak correlation between scores for foam pad, air-filled discs, Bosu® (dome up), Bosu® (dome down), and wobble board for both conditions. For unstable object rankings, there was a very strong correlation between scores (ρ=1.0, p = <.001). The objects were ranked by perceived difficulty as follows: Level 1 (easy)- ground, Level 2- foam pad, Level 3- air-filled discs, Level 4- Bosu®, and Level 5 (difficult)- wobble board.

Conclusion

Study findings suggest that actual measures of balance confidence may provide insight into a patient's confidence level and may help with prescribing and progressing their program. The suggested unstable object difficulty rankings may help professionals better match the objects to their patients to produce optimal outcomes.

Level of Evidence

2c.

Effect of push-up variations performed with Swiss ball on muscle electromyographic amplitude in trained men: A cross-sectional study

PURPOSE

To compare the use of three variations of push-ups: traditional (stable surface), performed with hands on the Swiss ball (Swiss ball-hands), and performed with feet on the Swiss ball (Swiss ball-feet) on surface electromyography activity (sEMG) in the agonist and stabilizer muscles.

METHODS

Ten trained men (26 ± 5 years, 76.8 ± 8.7 kg, 1.70 ± 0.06 m) performed one experimental protocol within-subjects in a randomized design. Each subject performed one set of 10 of each of the push-up variations (5-min rest between sets). The sEMG activity was assessed for pectoralis major, triceps brachii, anterior deltoids, and rectus abdominis. One-way repeated-measures ANOVA (Bonferroni) compared push-up variations within-muscles (p < 0.05).

RESULTS

Pectoralis major sEMG was similar between exercises. Anterior deltoid sEMG activity was greater for stable surface than for Swiss ball-hands (p = 0.001). Triceps brachii sEMG activity was greater during Swiss ball-hands than during stable surface (p = 0.001) and Swiss ball-feet (p = 0.043), and Swiss ball-feet was greater than stable surface (p = 0.001). Rectus abdominis sEMG activity was greater during Swiss ball-hands than during stable surface (p = 0.0001) and Swiss ball-feet (p = 0.036), while Swiss ball-feet was greater than stable surface (p = 0.046).

CONCLUSIONS

Push-ups performed with hands on the Swiss ball may be considered an advanced variation that should be used when the goal is to achieve greater challenge of the rectus abdominis and triceps brachii. Novice subjects or those with weakness/injury should perform push-ups with hands on a stable surface, and with progression, push-ups with feet on Swiss ball could be adopted before hands on Swiss ball.

Efficacy of whole-body suspension training on enhancing functional movement abilities following a supervised or home-based training program

BACKGROUND

The purpose of this study was to determine the effects of suspension training on functional movement and body composition, and to compare the effectiveness of home-based training to supervised training.

METHODS

Seventeen healthy subjects (8 males, 9 females, age=21.8±3.4 y) with no recent history of resistance training were randomly assigned to a home-based or supervised training group. Subjects performed an 8-week suspension training program consisting of 10 exercises targeting major muscle groups, twice per week for the duration of the study. Pre- and post-intervention testing included body composition using air displacement plethysmography, and a functional movement screen (FMS) to measure functional movement abilities.

RESULTS

The 8-week training program significantly improved total FMS scores across the whole sample of subjects (Pre=16.4; Post=17.5; P=0.004), with no differences in improvements between groups. When compared separately, only the supervised group significantly improved FMS scores. There was also a significant increase in lean mass across the total sample of subjects (Pre=52.4 kg; Post=53.3 kg; P=0.03) with no differences between groups. But when compared independently, neither group exhibited a significant increase in lean mass.

CONCLUSIONS

When completed as a whole-body exercise program over an 8-week period, suspension training can improve functional ability and increase lean mass in both a supervised and a home-based setting.

Activation of Scapular and Lumbopelvic Muscles During Core Exercises Executed on a Whole-Body Wobble Board

Context: Previous studies highlighted that exercises executed on unstable surfaces can yield important benefits to the function of the core musculature in rehabilitation settings, general conditioning settings, and athletic training when properly introduced within a periodized training schedule. No previous study has analyzed core-stability exercises executed in lying, quadruped, plank, and bridge positions on a whole-body wobble board (WWB) specifically designed to accommodate the exerciser’s entire body and promote whole-body instability. We have designed a WWB allowed to roll in a plane perpendicular to its longitudinal axis to promote proactive and reactive activation of the core muscles with a transverse or diagonal line of action, which provides trunk and pelvic stability with low spine compression forces. Purpose: To determine the effect of the use of this newly designed WWB by assessing differences in core-muscle activity during core-stability exercises performed on the ground, in a stable condition, and on the WWB. Design: Controlled laboratory study. Setting: Research laboratory. Patients or Other Participants: Eighteen participants recruited from fitness centers. Intervention(s): The electromyographic (EMG) activity of lumbopelvic and scapular muscles has been recorded during core-stability exercises executed on the WWB (unstable condition) and on ground (stable condition). Main Outcome Measure(s): Mean and peak EMG activity were compared between stable and unstable condition with paired t tests or Wilcoxon signed-rank tests. Results: Overall, exercises performed on the WWB yielded significantly higher EMG activity in the serratus anterior and anterolateral abdominal muscles compared with the same exercises executed on the ground. Conversely, for the bird dog exercise, lower-back muscle activity was significantly higher on the ground. Conclusions: Compared with the ground, core-stability exercises executed on WWB constitute a simple and effective strategy to increase the activity level of the core muscles that control transverse-plane lumbopelvic and trunk stability, avoiding the use of external overload.

Structure of force variability during squats performed with an inertial flywheel device under stable versus unstable surfaces

The use of unstable surfaces during resistance training has demonstrated a maintenance or reduction on force production. However, the use of unstable surface on force variability has not been assessed using non-linear methods that may be better suited to detect changes in movement variability throughout a given movement. Consequently, this study compared the use of stable vs unstable surfaces on force variability during bilateral squats performed with an inertial flywheel device (Eccoteck, Byomedic System SCP, Spain). Twenty healthy men (mean ± SD: age 22.9 ± 2.9 years, height 1.81 ± 0.7 m, body mass 76.4 ± 7.6 kg and 1RM back squat 110.9 ± 19.7 kg) with a minimum of four years in resistance training performed six sets of six repetitions of squats at maximal concentric effort with one minute rest between sets. Force output on the vertical axes was measured using a strain gauge and the results were processed using non-linear sample entropy (SampEn). Results showed no differences for any of the dependent variables between stable and unstable conditions. SampEn showed no differences between conditions (chi-squared = 0.048 P = 0.827), while Force_mean and SampEn presented a small correlation (r = 0.184; p < 0.01). No changes in entropy were found over the course of the series. Together, these results suggest that the structure of force variability between stable and unstable surfaces are similar. This lack of difference between surfaces may be due to postural and anticipatory adjustments. Consequently, by introducing unstable surfaces to the flywheel bilateral squat exercise, practitioners may not observe changes in Force_mean and force variability when compared to stable surface training suggesting that increased training volumes or intensity may be required during unstable environments to cause a desired training stimulus.

Instability training, assessing the impact of level of difficulty on balance: A randomized clinical trial

BACKGROUND

Most human movements are executed while in a state of postural instability. For this reason, instability training is a highly-specific method that is intended to improve balance and postural control. This research aimed to determine the effect of instability training on the balance of individuals with similar baseline abilities, who initiated training within different stability conditions.

RESEARCH QUESTION

Does the level of difficulty with which instability training is performed determine improvements in balance?

METHOD

A two-arm randomized trial was undertaken, for which 22 and 21 participants were included in the experimental and control groups, respectively. The experimental group performed balance training on unstable surfaces and the control group implemented the same training on stable ground. The primary outcome was the Y-Balance Test (YBT); the Emery test, Functional Reach test, and platform measures were the secondary outcomes. Confidence intervals were set at 95% and Cohen's f statistic was used to estimate effect size.

RESULTS

Dynamic balance, as measured by the YBT, showed significant Time improvements in both groups for right (p <  0.001, f = 0.53) and left (p =  0.005, f=0.33) limbs. Similar results were found in the Emery test and Functional Reach test. No statistical Group and Time*Group interactions were found. None of the proposals modified the center of pressure excursions.

SIGNIFICANCE

Instability training is a safe and effective approach to enhance balance. However, the findings deduced that the level of difficulty (instability) with which participants with similar abilities initiate the training is not a determining factor in the balance improvements achieved. It follows that instability training may be either used as an alternative or as an additional method to train for balance on a stable ground.

Sport-Specific Assessment of the Effectiveness of Neuromuscular Training in Young Athletes

Neuromuscular training in young athletes improves performance and decreases the risk of injuries during sports activities. These effects are primarily ascribed to the enhancement of muscle strength and power but also balance, speed and agility. However, most studies have failed to demonstrate significant improvement in these abilities. This is probably due to the fact that traditional tests do not reflect training methods (e.g., plyometric training vs. isometric or isokinetic strength testing, dynamic balance training vs. static balance testing). The protocols utilized in laboratories only partially fulfill the current needs for testing under sport-specific conditions. Moreover, laboratory testing usually requires skilled staff and a well equipped and costly infrastructure. Nevertheless, experience demonstrates that high-technology and expensive testing is not the only way to proceed. A number of physical fitness field tests are available today. However, the low reliability and limited number of parameters retrieved from simple equipment used also limit their application in competitive sports. Thus, there is a need to develop and validate a functional assessment platform based on portable computerized systems. Variables obtained should be directly linked to specific features of particular sports and capture their complexity. This is essential for revealing weak and strong components of athlete performance and design of individually-tailored exercise programs. Therefore, identifying the drawbacks associated with the assessment of athlete performance under sport-specific conditions would provide a basis for the formation of an innovative approach to their long-term systematic testing. This study aims (i) to review the testing methods used for the evaluation of the effect of neuromuscular training on sport-specific performance in young athletes, (ii) to introduce stages within the Sport Longlife Diagnostic Model, and (iii) to propose future research in this topic. Analysis of the literature identified gaps in the current standard testing methods in terms of their low sensitivity in discriminating between athletes of varied ages and performance levels, insufficent tailoring to athlete performance level and individual needs, a lack of specificity to the requirements of particular sports and also in revealing the effect of training. In order to partly fill in these gaps, the Sport Longlife Diagnostic Model was proposed.