Perceived Exertion: Revisiting the History and Updating the Neurophysiology and the Practical Applications

Acute hypoalgesic, neurophysiological and perceptual responses to low-load blood flow restriction exercise and high-load resistance exercise

This study compared the acute hypoalgesic and neurophysiological responses to low-load resistance exercise with and without blood flow restriction (BFR), and free-flow, high-load exercise. Participants performed four experimental conditions where they completed baseline measures of pain pressure threshold (PPT), maximum voluntary force (MVF) with peripheral nerve stimulation to determine central and peripheral fatigue. Corticospinal excitability (CSE), corticospinal inhibition and short interval intracortical inhibition (SICI) were estimated with transcranial magnetic stimulation. Participants then performed low-load leg press exercise at 30% of one-repetition maximum (LL); low-load leg press with BFR at 40% (BFR40) or 80% (BFR80) of limb occlusion pressure; or high-load leg press of four sets of 10 repetitions at 70% one-repetition maximum (HL). Measurements were repeated at 5, 45 min and 24 h post-exercise. There were no differences in CSE or SICI between conditions (all P > 0.05); however, corticospinal inhibition was reduced to a greater extent (11%-14%) in all low-load conditions compared to HL (P < 0.005). PPTs were 12%-16% greater at 5 min post-exercise in BFR40, BFR80 and HL compared to LL (P ≤ 0.016). Neuromuscular fatigue displayed no clear difference in the magnitude or time course between conditions (all P > 0.05). In summary, low-load BFR resistance exercise does not induce different acute neurophysiological responses to low-load, free-flow exercise but it does promote a greater degree of hypoalgesia and reduces corticospinal inhibition more than high-load exercise, making it a useful rehabilitation tool. The changes in neurophysiology following exercise were not related to changes in PPT.

Reference values for leg effort during incremental cycle ergometry in non-trained healthy men and women, aged 19-85

Heightened sensation of leg effort contributes importantly to poor exercise tolerance in patient populations. We aim to provide a sex- and age-adjusted frame of reference to judge symptom's normalcy across progressively higher exercise intensities during incremental exercise. Two-hundred and seventy-five non-trained subjects (130 men) aged 19-85 prospectively underwent incremental cycle ergometry. After establishing centiles-based norms for Borg leg effort scores (0-10 category-ratio scale) versus work rate, exponential loss function identified the centile that best quantified the symptom's severity individually. Peak O2 uptake and work rate (% predicted) were used to threshold gradually higher symptom intensity categories. Leg effort-work rate increased as a function of age; women typically reported higher scores at a given age, particularly in the younger groups (p < 0.05). For instance, "heavy" (5) scores at the 95th centile were reported at ~200 W (<40 years) and ~90 W (≥70 years) in men versus ~130 W and ~70 W in women, respectively. The following categories of leg effort severity were associated with progressively lower exercise capacity: ≤50th ("mild"), >50th to <75th ("moderate"), ≥75th to <95th ("severe"), and ≥ 95th ("very severe") (p < 0.05). Although most subjects reporting peak scores <5 were in "mild" range, higher scores were not predictive of the other categories (p > 0.05). This novel frame of reference for 0-10 Borg leg effort, which considers its cumulative burden across increasingly higher exercise intensities, might prove valuable to judging symptom's normalcy, quantifying its severity, and assessing the effects of interventions in clinical populations.

Day-to-day fluctuations of fatigue severity in individuals with knee osteoarthritis: an ecological momentary assessment approach

Objective

The variable course of fatigue adds to the disease burden of patients with OA yet it has been poorly understood. This study aimed to describe within-person fluctuations of fatigue severity and explore its associations with pain, positive affect, negative affect, sleep, and perceived exertion of physical activity.

Methods

Individuals with chronic knee pain or a clinical diagnosis of knee OA ≥40 years of age completed daily assessments about fatigue, pain, positive affect, negative affect, sleep, perceived exertion of physical activity (numeric rating scale 0-10), and overwhelming fatigue (yes/no) on a smartphone over 14 days. Within-person fluctuations of fatigue severity were described by the probability of acute changes (PACs) and s.d.s. Associations with pain, positive affect, negative affect, sleep, and perceived exertion of physical activity were explored using multilevel models.

Results

Forty-nine individuals were included (mean age 63.4 years; 82% female). PACs and s.d.s of within-person daily fatigue fluctuations ranged from 0.00 to 0.80 and 0.35 to 2.95, respectively. Within-person associations of fatigue severity were moderate for positive affect [β = -0.57 (95% CI -0.67, -0.47)], weak for pain [β = 0.41 (95% CI 0.29, 0.53)] and negative affect [β = 0.40 (95% CI 0.21, 0.58)], and negligible for sleep [β = -0.13 (95% CI -0.18, -0.08)] and perceived exertion of physical activity [β = 0.18 (95% CI 0.09, 0.26)].

Conclusion

Some individuals showed almost stable day-to-day levels of fatigue severity, whereas others experienced a substantial number of clinically relevant fluctuations. To reduce the burden of daily fatigue fluctuations, our results suggest that pain, positive and negative affect rather than sleep and perceived exertion of physical activity should be considered as potential targets.

Ventilatory response to peripheral chemoreflex and muscle metaboreflex during static handgrip in healthy humans: evidence of hyperadditive integration

NEW FINDINGS

What is the central question of this study? What is the effect of peripheral chemoreflex and muscle metaboreflex integration on ventilation regulation, and what is the effect of integration on breathing-related sensations and emotions? What is the main finding and its importance? Peripheral chemoreflex and muscle metaboreflex coactivation during isocapnic static handgrip exercise appeared to elicit a hyperadditive effect with regard to ventilation and an additive effect with regard to breathing-related sensations and emotions. These findings reveal the nature of the integration between two neural mechanisms that operate during small-muscle static exercise performed under hypoxia.

ABSTRACT

Exercise augments the hypoxia-induced ventilatory response in an exercise intensity-dependent manner. A mutual influence of hypoxia-induced peripheral chemoreflex activation and exercise-induced muscle metaboreflex activation might mediate the augmentation phenomenon. However, the nature of these reflexes' integration (i.e., hyperadditive, additive or hypoadditive) remains unclear, and the coactivation effect on breathing-related sensations and emotions has not been explored. Accordingly, we investigated the effect of peripheral chemoreflex and muscle metaboreflex coactivation on ventilatory variables and breathing-related sensations and emotions during exercise. Fourteen healthy adults performed 2-min isocapnic static handgrip, first with the non-dominant hand and immediately after with the dominant hand. During the dominant hand exercise, we (a) did not manipulate either reflex (control); (b) activated the peripheral chemoreflex by hypoxia; (c) activated the muscle metaboreflex in the non-dominant arm by post-exercise circulatory occlusion (PECO); or (d) coactivated both reflexes by simultaneous hypoxia and PECO use. Ventilation response to coactivation of reflexes (mean ± SD, 13 ± 6 l/min) was greater than the sum of responses to separated activations of reflexes (mean ± SD, 8 ± 8 l/min, P = 0.005). Breathing-related sensory and emotional responses were similar between coactivation of reflexes and the sum of separate activations of reflexes. Thus, the peripheral chemoreflex and muscle metaboreflex integration during exercise appeared to be hyperadditive with regard to ventilation and additive with regard to breathing-related sensations and emotions in healthy adults.

Reactive Agility and Pitching Performance Improvement in Visually Impaired Competitive Italian Baseball Players: An Innovative Training and Evaluation Proposal

Visual input significantly affects kinesthesis skills and, hence, visually impaired individuals show less developed sensorimotor control, especially in an unfamiliar outdoor environment. Regular blind baseball practice can counteract such a deficit but, given the complex kinetic chain model required, a targeted workout proposal is needed to improve the main athletic gesture performance. On these premises, we investigated, for the first time, the running and pitching performance of a competitive Italian blind baseball team through quantitative tools and parameters such as Libra Easytech sensorized proprioceptive board, goniometric active range of motion, chronometric speed, and pitching linear length. Moreover, the perceived physical exertion was assessed by the Borg CR10 scale. Consequently, an adapted athletic training protocol was designed and tested on the field during the competitive season, with the aim to strengthen sport specific-gesture coordination and efficacy as well as to prevent injuries. Quantitative assessments showed an improvement in ankle stability index, bilateral upper limb and hip mobility, reactive agility, running braking phase control during second base approaching, and auditory target-related pitching accuracy along with a decrease in perceived physical exertion. This protocol might therefore represent an effective and easily reproducible training and evaluation approach to tailor management of visually impaired baseball players, and safely improve their athletic performance under the supervision of an adapted exercise specialist.

Effects of personal protective equipment on cardiopulmonary resuscitation quality and outcomes: A systematic review

Background

The impact of wearing personal protective equipment (PPE) during cardiopulmonary resuscitation (CPR) on CPR quality and patient outcomes is unclear. This systematic review aimed to examine whether wearing PPE during resuscitation affects patient outcomes, CPR quality and rescuer fatigue.

Methods

In this review registered in PROSPERO (CRD42022347746), we searched Medline, EMBASE and Cochrane library between 2000 and 2022. The inclusion criteria were studies: in actual or simulated cardiac arrest; comparing PPE with no PPE; and randomised controlled trials and observational studies with a English abstract. Risk of bias was assessed using Cochrane's Risk of Bias-2 and ROBINS-I tools and outcomes assessed with GRADE. We conducted a meta-analysis according to the study design. Quantitative data synthesis was done using a random-effect model incorporating the potential heterogeneity.

Results

A total of 17 simulation-based studies and 1 clinical study were included. All outcomes were judged to be very low certainty of evidence, subject to high risk of bias. The clinical study showed no difference in survival comparing enhanced and conventional PPE. Meta-analysis of 11 RCTs and 6 observational studies found no difference in CPR quality in rescuers wearing PPE compared with no PPE. Pooled rescuer fatigue was significantly worse in the PPE group (mean difference, 2.7 VAS score out of 10; 95% CI, 1.4-4.0).

Conclusions

PPE was not associated with reduced CPR quality or lower cardiac arrest survival. Rescuers wearing PPE may report more fatigue. This finding was mainly derived from simulation studies, additional clinical studies are needed.

Moderate-Intensity Continuous Training Versus Moderate-Intensity Interval Training: Effects on Cardiometabolic Factors in Spanish Obese Adults

BACKGROUND

Excess weight and obesity are related to cardiometabolic diseases and limit physical activity. Until now, the effects of moderate-intensity continuous training (MICT) compared with moderate-intensity interval training (MIIT) in Spanish obese adults have not been analyzed.

OBJECTIVE

This study aimed to investigate the effect of MICT and MIIT together with a 1300-to-1400 caloric restrictive diet on cardiovascular disease risk factors in overweight and obese patients.

METHODS

The MICT and MIIT groups trained during 4 sessions a week for 12 weeks while performing the diet. The MICT group trained for 32 minutes per session in a cycloergometer, initially at 60% maximal oxygen uptake during the first month and increasing by 10% every 4 weeks. The MIIT group performed 4 × 4 intervals (at 60% maximal oxygen uptake and active rest at 60% maximal oxygen uptake minus 20 W), with a 10% increase every 4 weeks. The control group neither trained nor followed the restrictive diet.

RESULTS

One hundred fifty-nine obese adults participated in the study. The control group did not present any significant changes during the study. The MICT group significantly improved in all the variables (P < .05) except for high-density lipoproteins. The MIIT group improved in all the variables (P < .05) except for high-density lipoproteins and triglycerides. The MIIT group lost weight in less time than the MICT group.

CONCLUSIONS

Overweight and obese adults of both the MICT and MIIT groups decreased their risk for cardiovascular disease, although the MIIT group lost weight in a shorter amount of time.