Airflow restriction mask induces greater central fatigue after a non-exhaustive high-intensity interval exercise

The airflow restriction mask (ARM) is a practical and inexpensive device for respiratory muscle training. Wearing an ARM has recently been combined with high-intensity interval exercise (HIIE), but its effect on neuromuscular fatigue is unknown. The present study investigated the effects of ARM wearing on neuromuscular fatigue after an HIIE session. Fourteen healthy men performed two HIIE sessions (4x4min at 90% HRmax, 3min recovery at 70% HRmax) with or without an ARM. Neuromuscular fatigue was quantified via pre- to post-HIIE changes in maximal voluntary contraction (MVC), voluntary activation (VA, central fatigue), and potentialized evoked twitch force at 100, 10, and 1 Hz (peripheral fatigue). Blood pH and lactate were measured before and after the HIIE session, while HR, SpO₂ , dyspnea, physical sensation of effort (P-RPE), and Task Effort and Awareness (TEA) were recorded every bout. The exercise-induced decrease in MVC was higher (p<0.05) in the ARM (-28±12%) than in the control condition (-20±11%). The VA decreased (p<0.05) in the ARM (-11±9%) but not in the control condition (-4±5%, p>0.05). Pre- to post-HIIE declines in evoked twitch at 100, 10, and 1 Hz were similar (p>0.05) between ARM and control conditions (ARM: -18±10, -43±11 and -38±12%; Control: -18±14, -43±12 and -37±17%). When compared with the control, the HIIE bout wearing ARM was marked by higher heart rate, plasma lactate concentration, dyspnea, P-RPE and TEA, as well as lower SpO₂ and blood pH. In conclusion, ARM increases perceptual and physiological stress during a HIIE, which may lead to a greater post-exercise central fatigue.

The muscle contractile properties in female soccer players: inter-limb comparison using tensiomyography

OBJECTIVE

The present study aimed to: i) determine the contractile properties of the major lower limb muscles in female soccer players using tensiomyography; ii) investigate inter-limb differences; and iii) compare inter-limb differences between different selections and playing positions.

METHODS

A total of 52 female soccer players (A team; U19 and U17) were recruited. The vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), gastrocnemius medialis (GM), lateralis (GL) and tibialis anterior (TA) of both lower limbs were evaluated.

RESULTS

When the entire sample was assessed regardless of selection or playing position, there were significant inter-limb differences in all measured muscles except BF. Compared to the non-dominant limb, the dominant limb had higher delay time in VL (p=0.008), while showing lower values in VM (p=0.023), GL (p=0.043) and GM (p=0.006). Contraction time was lower in the RF of the dominant limb (p=0.005) and VM (p=0.047), while showing higher values in VL (p=0.036) and TA (p<0.001) as compared to the non-dominant limb.

CONCLUSION

Given the differences found between the limbs in the whole sample studied, it is necessary to examine both limbs to gather a more in-depth understanding of underlying mechanisms related to neuromuscular functions in female soccer players.

LEVEL OF EVIDENCE

Prognostic study, Level II.

Reliability of Hand-Held Dynamometer in Measuring Gluteal Muscle Rate of Torque Development and Peak Torque: Push and Pull Configurations

Background

Belt-stabilized handheld dynamometers (HHD) assess hip rate of torque development (RTD) and strength in research and clinical practice. However, the reliability of HHD with push and pull configurations to measure hip muscles RTD and peak torque is unclear.

Purpose/Hypothesis

To determine the intra- and inter-reliability of HHD utilizing push and pull configurations to measure hip abduction and extension early (0-100ms) and late (100-200ms) phases RTD and peak torque. We hypothesized HHD with both configurations would be reliable for measuring hip extension and abduction RTD and peak torque.

Study Design

Cross-sectional study.

Methods

Twenty healthy adults (10 females) performed three consecutive maximal isometric contraction trials of hip abduction and extension, utilizing an HHD with push and pull configurations by two raters. Each rater's average early and late phases RTD and peak torque of hip abduction and extension were utilized for analysis.

Results

Intra-rater reliability of hip abduction with push and pull configurations ranged moderate-to-good for early and late RTD phases (push: ICC2,1=0.61-0.88; pull: ICC2,1=0.59-0.75). Peak hip abduction torque showed good reliability in both configurations (ICC2,1≥0.79). Hip extension ranged moderate-to-good reliability for early and late RTD phases in push configuration (ICC2,1=0.72-0.87), with good-to-excellent reliability in pull (ICC2,1=0.77-0.91). Peak hip extension torque showed moderate-to-excellent reliability for push configuration (ICC2,1=0.73-0.92) and excellent reliability for pull (ICC2,1≥0.91). Inter-rater reliability for hip abduction showed moderate in push (ICC3,k≥0.72) and good in pull (ICC3,k≥0.78) configurations for both RTD phases, while hip extension showed good reliability in push (ICC3,k≥0.82) and excellent reliability in pull (ICC3,k≥0.95) configurations. Peak torque showed good reliability for hip abduction (ICC3,k≥0.83) and excellent reliability for extension (ICC3,k≥0.94) in both configurations.

Conclusions

HHD with push and pull configurations is a reliable and cost-effective method for assessing RTD and strength of hip abductors and extensors in healthy adults.

Level of Evidence

Level 3.

The importance of neuromuscular rate of force development for physical function in aging and common neurodegenerative disorders - a systematic review

We systematically reviewed existing literature regarding lower extremity neuromuscular rate of force development (RFD), maximal muscle strength (Fmax), and physical function in neurodegenerative populations, and to what extent these outcomes are affected and/or associated. Following PRISMA guidelines, 4 databases (Pubmed, Embase, SPORTDiscus, Web of Science) were searched. Across aging, Parkinson Disease (PD), Alzheimer's Disease (AD), Multiple Sclerosis (MS), or Stroke, included studies should report (Part 1) deficits in lower extremity RFD, Fmax, and physical function (~ individuals having inferior vs. superior physical function), and/or (Part 2) associations between RFD (or Fmax) and physical function. A total of N=32 studies (n=1087 participants) were included. Part 1: deficits in RFD (-31%, mean; N=22) were comparable to deficits in physical function (-26%; N=7), yet both deficits exceeded that of Fmax (-21%; N=20). Part 2: associations between RFD and physical function (r2=0.13, mean; N=16) were comparable to associations between Fmax and physical function ((r2=0.15; N=12). Lower extremity RFD is (1) particularly sensitive (i.e. adapts earlier and/or more extensively) towards neurodegeneration, and more so than Fmax, and (2) of importance for physical function but apparently not superior to Fmax. RFD could serve as a useful indicator/biomarker of changes in neuromuscular function elicited by neurodegeneration.