Force production during maximal front crawl tethered swimming: exploring bilateral asymmetries and differences between breathing and non-breathing conditions

The present study focused on propulsive forces applied during tethered swimming. The main aims were to identify asymmetries between dominant and non-dominant arms, quantify the effect of breathing on force application and, explore any association between each variable and swimming performance. Fifteen regional level swimmers completed a maximal front crawl tethered swimming test, with maximal kicking, under four conditions: 1) Dominant arm strokes only, no breathing; 2) non-dominant arm strokes only, no breathing; 3) full stroke, no breathing; 4) full stroke, breathing on the preferred side. The outcome variables were: absolute and normalised (force divided by body mass) minimum, mean and maximum force; stroke cycle time and; impulse. The symmetry index was also calculated, and all variables were correlated with the swimmers' season best times in 50 m front crawl. Some bilateral force asymmetries were found, but they did not always favour the dominant side and were not directly linked with swimming performance. There was no strong evidence that force production is higher on the dominant side or that symmetry in force production affects performance. Despite the longer stroke cycle times when breathing, the breathing actions did not affect force production. Faster swimmers often produced higher maximum force values and, sometimes, higher mean force values.

The effect of back squat depth and load on lower body muscle activity in group exercise participants

Les Mills BODYPUMPTM is a resistance training group exercise class with a low load, high repetition format. Squat training in BODYPUMPTM has two key variables: depth and load. The study aim was to determine the effect of these parameters on the mean and peak EMG amplitude of vastus lateralis, gluteus maximus, biceps femoris and lateral gastrocnemius. Ten female BODYPUMPTM participants (age 41 ± 9 years, height 161.9 ± 3.8 cm, mass 67.7 ± 7.0 kg) performed 1 × 7 squats under four conditions, representing every combination of two depths (90° knee angle and 125° knee angle) and two loads (23% bodyweight and 38% bodyweight). The main effect of depth was significant for mean and peak activity of vastus lateralis and gluteus maximus, and peak activity of biceps femoris and lateral gastrocnemius. The main effect of load was significant for mean and peak activity of gluteus maximus and lateral gastrocnemius. There was no depth * load interaction. These data can be used to inform BODYPUMPTM programme design and amplify the training effect of participation in group exercise classes.

Which Phases of the Stroke Cycle Are Propulsive in Front Crawl Swimming?

Purpose: The aim of this study was fourfold: (1) to quantify acceleration, velocity, and phase overlap for each phase of the stroke cycle (SC) during 200 m front crawl; (2) for each variable, to identify any differences between the four SC phases; (3) to investigate changes in variables during the 200 m; (4) to explore any association between performance and each variable. Methods: Ten swimmers performed a 200 m maximum swim. Four SCs were analyzed, one for each 50 m, using three-dimensional methods. Each SC was split into four phases: entry, pull, push, and recovery. Center of mass (CM) acceleration; maximum, minimum, and average CM velocity; phase duration, and, overlap of a phase of one arm with each phase of the opposite arm were calculated. Results and Conclusion: Phase velocities were positively correlated with performance and decreased during the 200 m. The acceleration data showed high within and between-swimmer variability. When the entry of one arm overlapped with the pull, and sometimes push, phase of the opposite arm, it was propulsive for the whole body. The pull was the slowest phase and overlapped predominantly with the opposite arm's recovery. The push phase was often propulsive for the whole body, regardless of the overlaps with the other arm, and together with the entry were the fastest phases. The recovery of each arm was mostly resistive for the whole body, except the short period of overlap with the opposite arm's push phase.

Effect of High-Intensity Interval Training on Functional Movement in Older Adults: A Systematic Review and Meta-analysis

BACKGROUND

Preserving physiological functional capacity (PFC), the ability to perform the activities of daily life, and the ease with which they can be performed, in older adults, defined for this study as ≥ 50 years of age, is an important consideration for maintaining health and independence through the ageing process. Physical activity, and exercise training in particular, has been positively associated with improvement in PFC. In addition to improving aerobic and anaerobic capacity, promoting and preserving functional movement as a component of PFC is an important goal of physical activity, especially for older adults. High-intensity interval training (HIIT), an exercise protocol where repeated bouts of increased intensity are interspersed with active or passive recovery periods, has often been studied as an alternative to traditional moderate-intensity continuous training (MICT) exercise, where a continuous intensity is maintained throughout the exercise session. A large body of research has determined that both types of exercise programme are effective in improving measures of aerobic and anaerobic fitness in older adults. However, the effect of the two exercise modalities on functional movement has most often been a secondary outcome, with a range of observational techniques applied for measurement.

OBJECTIVES

The primary objective of this research is to systematically review and meta-analyse published studies of HIIT interventions that measured functional movement in older adults to conclude if HIIT is effective for improving functional movement. A secondary objective is to determine if there are significant differences between HIIT and MICT effect on functional movement.

METHODS

A search strategy of terms locating studies of HIIT interventions, functional movement outcome measures, and older adult population samples was executed on seven digital databases. Randomized and pair-matched trials of > 2 weeks were considered for inclusion. Studies of participants with neurological impairment or studies using combined exercise modality were rejected. Standardized mean difference for functional movement outcome measures was calculated. A meta-analysis of the included studies and subgroups was performed along with study quality (risk of bias and publication bias) evaluation.

RESULTS

A total of 18 studies were included in random effects model pooled analysis. Subgroup analysis of HIIT versus MICT on functional movement showed a trivial effect in favour of HIIT (ES 0.13, 95% CI [-0.06, 0.33] p = 0.18) and did not achieve statistical significance. However, HIIT showed a medium, statistically significant favourable effect on functional movement versus non-intervention control (ES = 0.60 95% CI [0.24, 0.95] p = 0.001). Further subgroups analysis using singular and multiple functional movement outcome measures showed similar results.

CONCLUSION

This meta-analysis indicates that HIIT interventions in older adults may be effective at promoting improvements in functional movement, though it is unclear whether HIIT is superior to MICT.

The WATER study: Which AquaTic ExeRcises increase muscle activity and limit pain for people with low back pain?

OBJECTIVE

Aquatic exercise therapy is used for the treatment and management of chronic low back pain (CLBP). However, to the authors' knowledge, no studies to date have compared muscle activity between different aquatic exercises performed by people with CLBP. As such, this study assessed and compared muscle activity, pain, perceived exertion and exercise intensity between different rehabilitative aquatic exercises.

DESIGN

Cross-sectional.

SETTING

A 25-m indoor swimming pool within a university building.

PARTICIPANTS

Twenty participants with non-specific CLBP.

ASSESSMENT

Twenty-six aquatic exercises in shallow water (1.25-m depth). Muscle activity was quantified bilaterally for the erector spinae, multifidus, gluteus maximus and medius, rectus abdominis, and external and internal obliques.

MAIN OUTCOMES

Mean and peak muscle activity, pain (visual analogue scale), perceived exertion (Borg scale) and exercise intensity (heart rate).

RESULTS

Hip abduction/adduction and extension/flexion exercises produced higher activity for gluteal muscles. Variations of squat exercises increased the activity of back extensors. Higher abdominal muscle activity was produced with exercises that made use of buoyancy equipment and included leg and trunk movements while floating on the back, and with some proprioceptive and dynamic lower limb exercises. Pain occurrence and intensity were very low, with 17 exercises being pain free.

CONCLUSIONS

This study provides evidence on trunk and gluteal muscle activity, pain, intensity and perceived exertion for people with CLBP performing aquatic exercises. The findings may be useful when prescribing exercises for rehabilitation, as physiotherapists seek to implement progression in effort and muscle activity, variation in exercise type, and may wish to target or avoid particular muscles. CONTRIBUTION OF THE PAPER.

The Effects of British Army Footwear on Ground Reaction Force and Temporal Parameters of British Army Foot Drill

Rawcliffe, AJ, Graham, SM, Simpson, RJ, Moir, GL, Martindale, RJ, Psycharakis, SG, and Connaboy, C. The effects of British Army footwear on ground reaction force and temporal parameters of British Army foot drill. J Strength Cond Res 34(3): 754-762, 2020-High rates of occupational training-related lower-limb musculoskeletal (MSK) overuse injuries are reported for British Army recruits during basic training. Foot drill is a repetitive impact loading occupational activity and involves striking the ground violently with an extended-knee (straight-leg) landing. Foot drill produces vertical ground reaction force (vGRF) equal to or greater than those reported for high-level plyometric exercises/activities. Shock absorbing footwear aid in the attenuation of the magnitude of vGRF, resulting in a reduced risk of lower-limb MSK overuse injury when running. The potential shock absorbing characteristics of standard issue British Army footwear on the magnitude of vGRF and temporal parameters of foot drill are scant. Therefore, this study sought to determine the magnitude of and examine changes in vGRF and temporal parameters of foot drill across 3 types of British Army footwear. Sampled at 1,000 Hz, the mean of 8 trials from 15 recreationally active men were collected from 4 foot drills; stand-at-ease, stand-at-attention, quick-march (QM), and halt. Analysis of a normal walk was included to act as a comparison with QM. Significant main effects (P ≤ 0.05) were observed between footwear and foot drill. The training shoe (TR) demonstrated significantly greater shock absorbing capabilities when compared with the combat boot and ammunition boot. Foot drill produced peak vGRF and peak vertical rate of force development in excess of 5 bw, and 350 bw·s, respectively. Time to peak vGRF ranged from 0.016 to 0.036 ms across foot drills, indicating that passive vGRF may not be under neuromuscular control. The marginal reductions in the magnitude of vGRF and temporal parameters in foot drill associated with the TR may act to reduce the accumulative impact loading forces experienced by recruits, subsequently minimizing the severity and rates of lower-limb MSK overuse injuries and recruit medical discharges during basic training.

Effects of Additional Load on the Occurrence of Bilateral Deficit in Counter-Movement and Squat Jumps

Purpose: A vertical jump (VJ) is a common task performed in several sports, with the height achieved correlated to skilled performance. Loaded VJs are often used in the training of recreational and professional athletes. The bilateral deficit (BLD), which refers to the difference between the heights achieved by a bilateral jump and the sum of two unilateral jumps, has not been reported for loaded jumps and the findings for unloaded jumps are inconclusive. The purpose of this study was threefold: (a) to quantify and compare BLD in countermovement (CMJ) and squat jumps (SJ), (b) to explore the effects of an additional 10% of body weight (BW) load on the BLD in both CMJ and SJ, and (c) examine the relationship between magnitude of BLD and jump performance in both jumps and conditions. Methods: Forty participants (22 for CMJ and 18 for SJ) performed a bilateral jump and unilateral jumps on each leg with and without an added load equivalent to 10% of each participant's bodyweight. Results: BLD was evident in all conditions, with CMJ BLD values nearly double those for the SJ. The extra load did not affect the magnitude of BLD. BLD had a significant correlation with unilateral jump height, expect for the 110%BW SJ. Conclusions: BLD is present in SJs and CMJs at both loaded and unloaded conditions. The SJs have about half of the BLD observed in CMJs regardless of additional load. Participants who had higher single leg jumps seemed to also have higher BLDs, but there was no evidence of association between the bilateral jump height and BLD.

Muscle Activity During Aquatic and Land Exercises in People With and Without Low Back Pain

BACKGROUND

Chronic low back pain (CLBP) is the most prevalent musculoskeletal disorder. Aquatic exercises are commonly used by physical therapists for CLBP treatment and management; however, there are no data on trunk muscle activation during aquatic exercises in people with CLBP.

OBJECTIVE

We quantified activation of trunk and gluteal muscles, exercise intensity, pain, and perceived exertion in people with and without CLBP when performing water and land exercises.

DESIGN

The study used a cross-sectional design.

METHODS

Twenty participants with nonspecific CLBP and 20 healthy participants performed 15 aquatic exercises and 15 similar land exercises. Mean and peak muscle activation were measured bilaterally from erector spinae, multifidus, gluteus maximus, gluteus medius, rectus abdominis, external oblique, and internal oblique using waterproof and wireless surface electromyography. Exercise intensity (heart rate), perceived exertion (Borg scale), and, for the CLBP group, pain (visual analog scale) were recorded.

RESULTS

There were no significant between-group differences. Significant between-environment differences were found in heart rate (always higher on land), exertion (higher in the water for 3 exercises and on land for 6 exercises), and muscle activation (higher on land in 29% and in the water in 5% of comparisons). Pain levels were low, but pain was reported more than twice as frequently on land than in water (7.7% vs 3.7%, respectively).

LIMITATIONS

People with high levels of disability and CLBP classification were not included.

CONCLUSIONS

People with mild-to-moderate CLBP had similar exercise responses to healthy controls. Aquatic exercise produced sufficient muscle activation, intensity, and exertion, and should not be assumed to be less strenuous or less effective in activating trunk and pelvic muscles than exercise on land. These data can be used to inform design and prescription of rehabilitation programs and interventions.

Reliability of the elliptical zone method of estimating body segment parameters of swimmers

Due to the difficulty of measuring forces and torques acting on a swimmer during mid-pool swimming, an inverse dynamics approach is required. Personalised body segment parameter (BSP) data enabling calculation of net forces and torques can be obtained using the elliptical zone method. The purpose of this study was to establish the reliability of estimating BSP data of swimmers by the elliptical zone method with segment outlines being traced manually on a personal computer screen. Five assessors digitised the segment landmarks and traced the body segments from front and side view digital photographs of 11 single arm amputee swimmers. Each swimmer was assessed five times by each of the five assessors. The order was fully randomised. Within assessor variability was less than 5% for the segment centre of mass position of all segments, for segment length except the neck (5.2%), and for segment mass except neck (11.9%), hands (Left: 8.1%; Right: 5.8%) and feet (Left: 7.3%; Right: 7.3%). Analysis of mean variability within and between assessors indicated that between assessor variability was generally as large or larger than within assessor variability. Consequently it is recommended that when seeking personalised BSP data to maximise the accuracy of derived kinetics and sensitivity for longitudinal and bilateral within-subject comparisons the individual should be assessed by the same assessor with mean values obtained from five repeat digitisations. This study established that using the elliptical zone method using E-Zone software is a reliable and convenient way of obtaining personalised BSP data for use in analysis of swimming. Key pointsA unique (not been attempted previously) study of reliability of calculating personalised Body Segment Parameter (BSP) data using the elliptical zone methodEstablishes benchmark data regarding the reliability of BSP data for comparison with emerging technologies for obtaining personalised BSP data non-invasively.Provides a description and guidelines for good practice for maximising the accuracy of derived kinematics and kinetics in swimming.The method of body modelling described can also be applied to studies in other sports and in assessing change in health status related to body shape characteristics for sport and non-sport populations.

Comparison of the effects of active, passive and mixed warm ups on swimming performance

AIM

The aim of this paper was to compare the effects of an active (AWU), passive (PWU) and mixed warm up (MWU) on swimming performance.

METHODS

Eight male competitive swimmers completed each type of WU and, following a 20-minute rest, performed a maximum 100m test on their specialised stroke. The order of WUs was randomized and there was a 7-day period between subsequent testing sessions. The time taken to complete the 100m trial was the performance measure. The rating of perceived exertion (RPE) was measured immediately post WU, while heart rate (HR) was measured pre and post WU and pre and post the maximum swim. During the 20-minute rest, the swimmers' psychological state was assessed with the CSAI-2 questionnaire.

RESULTS

Post WU HR and RPE had the lowest values following the AWU and the highest values following the PWU (P<0.01). No other significant differences were found in any variables. Pre performance HR increased significantly relative to pre WU HR for all conditions (P≤0.01). Swimmers had relatively low levels of anxiety and modest to high levels of self confidence for all conditions.

CONCLUSIONS

No WU appeared to be superior to the others with respect to swimming performance. The MWU produced nearly identical values to the AWU for most variables, and was therefore found to be an appropriate alternative WU type that swimmers may use before competition. The PWU also seemed to be appropriate, but the somewhat worse performance and lower cognitive anxiety and self confidence scores recorded, albeit non-significant, suggested that more swimmers and distances are tested before any firm conclusions regarding its effectiveness can be drawn.

A longitudinal analysis on the validity and reliability of ratings of perceived exertion for elite swimmers

The purpose of this study was to examine longitudinally the reliability and validity of ratings of perceived exertion (RPE) for monitoring exercise intensity in elite swimmers, with the percentage of maximum heart rate (%HRmax) and the blood lactate concentration (La) being the criterion measures. Moreover, the purpose was to examine whether an adjustment of HRmax, as previously suggested for recreational/university swimmers, is required for subsequent calculations of %HRmax for elite swimmers. Seventeen swimmers competing at international level performed a 7 x 200 m incremental swim test at their specialty stroke 4 times during a period of 6 months. The RPE validity was examined with the use of correlation and with repeated measures analysis of variance (ANOVA) of the z-transformed values. The RPE reliability was examined with a factorial ANOVA, with %HRmax and La being the dependent variables and test (4 levels) and RPE stage (7 levels) the fixed factors. The RPE was found to be a valid method for monitoring exercise intensity, with the correlation coefficients with %HRmax and La being 0.85 and 0.82, respectively. There was a strong correspondence between RPE and %HRmax scores and a weaker correspondence between RPE and La scores, suggesting that that RPE reflects accurately the HR levels of elite swimmers. The longitudinal intertest reliability was high as no significant differences were found in the values of %HRmax or La between the 4 tests. The good validity and reliability of RPE suggest that it can be used in elite swimmers' training for the purpose of monitoring exercise intensity. Contrary to previous recommendations for recreational/university swimmers, when prescribing intensity for elite swimmers, the predicted HRmax value used for subsequent calculations should not be adjusted because such an adjustment would appear to underestimate HRmax.

Analysis of selected kinematic and physiological performance determinants during incremental testing in elite swimmers

This study examined the relationships between selected kinematic and physiological parameters and their influence on performance during incremental exercise in elite swimmers competing at the international level. Eleven men and ten women (all specialized in 200-m events) performed an incremental 7 x 200-m test in their specialized stroke. Stroke rate (SR), stroke length (SL), velocity (V), and blood lactate concentration (BLa) were measured for each 200 m. In addition to the cross-sectional group design, the longitudinal performance of a male swimmer was evaluated by 4 tests during a period of 20 weeks. Stroke rate increased and SL decreased with V, regardless of the age, stroke, or gender of the swimmer. Statistically significant correlations were found between SR and V (p < 0.01; r = 0.66 to 0.99), SR and SL (p < 0.01; r = -0.78 to -0.99), SL and V (except for women's freestyle and breaststroke) (p < 0.01; r = -0.67 to -0.98), and BLa and V (p < 0.01; r = 0.7 to 0.96). Changes in SR and SL were not affected by changes in BLa. Similar velocities were produced with different combinations of SR and SL. The fastest times reached in the test were generally slower than expected, and the performance in the test was not associated with competition performance. The case study revealed similar results to those of the group. The test used in this study was informative with respect to identifying the most economical and effective stroke kinematics combination for slow to submaximal velocities. It is possible that the swimming speeds were not maximal in the final 200-m swim because of cumulative fatigue, which is a major limitation for assessing race pace. An additional test that produces velocities similar to those used in competitions would be more useful for the purpose of providing optimal kinematic information specific to racing speeds, which would facilitate performance improvement through regular monitoring in training.

Validity of the use of a fixed point for intracycle velocity calculations in swimming

The intracycle velocity (V) of a fixed point on a swimmer's body, usually the hip, is frequently calculated as a direct indication of the intracycle V of the centre of mass (CM). The purpose of this study was to examine whether the intracycle V of the hip reflects accurately the intracycle V of the CM in freestyle swimming. One stroke cycle was analysed for ten swimmers performing a maximum freestyle swim. The magnitude of differences between CM and hip values was calculated for the instantaneous V values, the intracycle V fluctuation (V(fluc)) and the magnitude and timing of appearance of maximum (V(max)) and minimum intracycle V (V(min)). Large differences were found in all variables, with the use of the hip for V calculations overestimating significantly V(max) and underestimating significantly V(min) and V(fluc) of the CM (p< or =0.001). The results of this study showed that the hip motion should not be used as an indication of the intracycle CM motion in freestyle swimming.