THE IMPACT OF LIMB SYMMETRY ON STROKE-TO-STROKE MOVEMENT VARIABILITY IN PARA-SWIMMERS DURING AN ADAPTED AEROBIC STEP TEST

The study purpose was to measure effects of anthropometric limb characteristics on fatigue-related changes in stroke-to-stroke motor variability (MV) of trunk mediolateral (ML) acceleration. Six Paralympic swimmers performed an in-water, fatiguing, freestyle aerobic test consisting of 5 steps of 200m (n = 4); 150m (n = 1) or 100m (n = 1) with a sacrum worn inertial measurement unit. Upper-limb segment lengths were measured, and symmetry indices (LSI) were calculated. Sample entropy (SampEn) and fractal dimension (FD) were calculated on ML acceleration. Fatigue was confirmed with increased RPE (p \u3c 0.01). ANOVA fatigue response models of SampEn and FD improved with LSI as a covariate (p \u3c 0.01), showing that symmetry indices affected individual responses to fatigue. Coaches should consider anthropometric symmetry when designing para-swimming training plans

Is sex a proxy for mechanical variables during an upper limb repetitive movement task? An investigation of the effects of sex and of anthropometric load on muscle fatigue

Abstract Background Women report more work-related pain and neck/shoulder musculoskeletal disorders than men. For the same absolute workload, due to lower strength, females generally work at a higher relative intensity, which could induce more fatigue. However, the arm’s anthropometric load (AL) of men is higher. Therefore, simply lifting their arm could be more fatiguing. Sex as a variable is formed of many constructs, and analyses can become muddied by their differing responses to fatigue. No studies have considered AL, when comparing how fatigue affects men and women. The purpose was to determine if including the arm’s AL in the statistical analysis would impact findings of sex-specific effects of shoulder fatigue on muscle EMG. Methods Fifty-five (29m/26f) participants completed a repetitive pointing task (RPT) at shoulder height until they reported fatigue of 8+ on the BORG CR-10 scale. Muscle activities were measured using surface electrodes placed over the anterior deltoid (AD) and upper trapezius (UT) muscles. Muscle activity amplitude was quantified using root mean square (RMS). First- and last-minute data were used to assess change from no-fatigue (NF) to fatigue-terminal (FT) conditions. AL was calculated using sex-specific body parameter equations. General estimating equations (GEE) were used to determine the effects of sex and fatigue on RMS values, while including AL in the GEE. Results There was no sex difference in time to reach fatigue. A significant main effect of sex on RMS was observed (χ2(1) = 4.17, p = 0.04) when including AL as a covariate. Females displayed a significantly higher percentage change in AD RMS from NF to FT, compared to males (p = 0.03), when AL was included in the GEE. No sex differences in UT were observed. Conclusions This sex difference emerged when AL was included as a covariate, suggesting that sex-associated anthropometric differences may contribute to sex differences in the fatigue response. Differences in the impact of AL on AD compared to UT could be explained by differences in their respective mechanical roles or muscle fiber content. Anthropometrics may be useful to include as covariates in future research to separate individual anthropometric differences from sex differences. </jats:sec

Measuring the Impact of Limb Asymmetry on Movement Irregularity and Complexity Changes During an Incremental Step Test in Para-Swimmers Using Inertial Measurement Units

Wearable technology can nowadays be used to improve para-swimming coaching; however, the extent to which individual anatomy affects features of swimming variability is unclear. Six paralympic swimmers were recruited, their upper-limb segment lengths were measured, and their absolute bilateral limb asymmetry indices (AbsLAIUL) were calculated. They were instrumented with a sacrum-worn inertial measurement unit and performed an in-water, fatiguing, freestyle aerobic test at incrementally faster paces. Stroke-to-stroke outcome and execution variability were calculated, respectively, using sample entropy (SampEn) and fractal dimension (FD) on forward and mediolateral linear acceleration signals. Significantly increased perceived exertion scores (F(4,28) = 154.1, p &lt; 0.001) were observed. Execution and outcome variability increased in the forward (SampEn = F(4,25) = 11.86, p &lt; 0.001; FD = F(4,24) = 6.17, p = 0.001) and mediolateral (SampEn = F(4,25) = 9.46, p &lt; 0.001; FD = F(4,24) = 27.64, p &lt; 0.001) directions. Modelling of FD (only) improved with AbsLAIUL as a covariate (forward = F(1,24) = 9.68, p = 0.005; mediolateral = F(1,24) = 8.57, p = 0.021), suggesting that AbsLAIUL affects only execution, but not outcome, variability. This information could help coaches determine which coordination indices should be personalized when monitoring variability during para-swimming training

Validation of Automatically Quantified Swim Stroke Mechanics Using an Inertial Measurement Unit in Paralympic Athletes

Biomechanics and training load monitoring are important for performance evaluation and injury prevention in elite swimming. Monitoring of performance and swim stroke parameters is possible with inertial measurement units (IMU) but has not been validated in para-swimmers. The purpose of this study was to validate a single IMU-based system to accurately estimate pool-swam lap time, stroke count (SC), stroke duration, instantaneous stroke rate (ISR), and distance per stroke (DPS). Eight Paralympic athletes completed 4 &times; 50 m swims with an IMU worn on the sacrum. Strokes cycles were identified using a zero-crossing algorithm on the medio-lateral (freestyle and backstroke) or forward-backward (butterfly and breaststroke) instantaneous velocity data. Video-derived metrics were estimated using Dartfish and Kinovea. Agreement analyses, including Bland&ndash;Altman and Intraclass Correlation Coefficient (ICC), were performed on all outcome variables. SC Bland&ndash;Altman bias was 0.13 strokes, and ICC was 0.97. ISR Bland&ndash;Altman biases were within 1.5 strokes/min, and ICCs ranged from 0.26 to 0.96. DPS Bland&ndash;Altman biases were within 0.20 m, and ICCs ranged from 0.39 to 0.93. A single-IMU system can provide highly valid performance and swim stroke monitoring data for elite para-swimmers for the majority of strokes, with the exception of backstroke. Future work should improve bilateral stroke detection algorithms in this population