Background: Despite widespread use of the incremental shuttle walk distance (ISWD), there are no reference equations for predicting it. Objectives: We aimed to evaluate ISWD in healthy subjects and to establish a reference equation for its prediction. Methods: 131 Brazilian individuals (61 males; 59 ± 10 years) performed 2 walk tests in a 10-m long corridor. We assessed height, weight, body mass index, forced expiratory volume in 1 s, forced vital capacity and self-reported physical activity. Results: Mean ISWD was greater in males than in females (606 ± 167 vs. 443 ± 117 m; p < 0.001). ISWD correlated significantly (p < 0.05) with age (r = –0.51), height (r = 0.54) and weight (r = 0.20). A predictive model including age, height, weight and gender explained 50.3% of the ISWD variance. In an additional group of 20 subjects prospectively studied, the difference between measured and predicted ISWD was not statistically significant (534 ± 84 vs. 552 ± 87 m, respectively), representing 97 ± 12% of the predicted value calculated with our reference equation for ISWD. Conclusions: This reference equation including demographic and anthropomorphic attributes could be useful for interpreting the walking performance of patients with chronic diseases that affect exercise capacity.

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We compared the effect of three different exercise programs on patients with chronic obstructive pulmonary disease including strength training at 50-80% of one-repetition maximum (1-RM) (ST; N = 11), low-intensity general training (LGT; N = 13), or combined training groups (CT; N = 11). Body composition, muscle strength, treadmill endurance test (TEnd), 6-min walk test (6MWT), Saint George's Respiratory Questionnaire (SGRQ), and baseline dyspnea (BDI) were assessed prior to and after the training programs (12 weeks). The training modalities showed similar improvements (P > 0.05) in SGRQ-total (ST = 13 ± 14%; CT = 12 ± 14%; LGT = 11 ± 10%), BDI (ST = 1.8 ± 4; CT = 1.8 ± 3; LGT = 1 ± 2), 6MWT (ST = 43 ± 51 m; CT = 48 ± 50 m; LGT = 31 ± 75 m), and TEnd (ST = 11 ± 20 min; CT = 11 ± 11 min; LGT = 7 ± 5 min). In the ST and CT groups, an additional improvement in 1-RM values was shown (P < 0.05) compared to the LGT group (ST = 10 ± 6 to 57 ± 36 kg; CT = 6 ± 2 to 38 ± 16 kg; LGT = 1 ± 2 to 16 ± 12 kg). The addition of strength training to our current training program increased muscle strength; however, it produced no additional improvement in walking endurance, dyspnea or quality of life. A simple combined training program provides benefits without increasing the duration of the training sessions.

We aimed to examine whether the ventilatory threshold (VT) during an incremental shuttle walk test (ISWT) could be determined using heart rate variability (HRV) analysis. Further aims were to assess variables capable of predicting performance in the ISWT and the intensity of this test. Beat-to-beat RR intervals and gas exchange values in 10 healthy subjects (31-83 years; 7 men) were collected during the ISWT. The ventilatory equivalent was used to assess VT from respiratory components. To determine the HRV threshold (HRVT), the instantaneous beat-to-beat variability values of the RR intervals at each stage of exercise were graphically plotted against walking speed (WS). The oxygen consumption at HRVT was calculated (VO2HRVT). No significant differences were found between walking speed (WS) at VT and WS at HRVT (5.04±1.00 vs. 5.10±1.04  km/h; p=0.89). Linear regression analysis revealed a strong correlation between VO2VT and VO2HRVT (r(2)=0.896). The Bland and Altman plot analysis revealed an agreement between VO2VT and VO2HRVT (-0.05; 95%CI: -0.30-0.20  L/min). Thus, the VT can be assessed during the ISWT using a simple heart monitor. The ISWT may be a useful tool to assess exercise capacity and prescribe walking programs.

OBJECTIVE: To determine reference values for incremental shuttle walk distance (ISWD) and peak physiological responses during the incremental shuttle walk test (ISWT), as well as to develop a series of predictive equations for those variables in healthy adults. METHODS: We evaluated 103 healthy participants ≥ 40 years of age (54 women and 49 men). We fitted each participant with a gas analysis system for use during the ISWT. Oxygen consumption (VO2), carbon dioxide production, minute ventilation, heart rate (HR), ISWD, and maximal walking velocity (MWV) were obtained as primary outcomes. We also assessed hand grip strength (HGS) and lean body mass (LBM). RESULTS: The regression analysis models, including physiological variables, ISWD, and MWV (adjusted for age, body mass, height, and sex), produced R2 values ranging from 0.40 to 0.65 (for HR and peak VO2, respectively). Using the models including LBM or HGS, we obtained no significant increase in the R2 values for predicting peak VO2, although the use of those models did result in slight increases in the R2 values for ISWD and MWV (of 8% and 12%, respectively). The variables ISWD, MWV, and ISWD × body mass, respectively, explained 76.7%, 73.3%, and 81.2% of peak VO2 variability. CONCLUSIONS: Our results provide reference values for ISWD and physiological responses to the ISWT, which can be properly estimated by determining simple demographic and anthropometric characteristics in healthy adults ≥ 40 years of age. The ISWT could be used in assessing physical fitness in the general adult population and in designing individualized walking programs.