Exercise--Physiological aspects

Effects of an external nasal dilator on the work of breathing was measured during exercise in 14 untrained students (age, 24 $\pm$ 3 yr.). Two maximal, incremental ergometer tests were performed to exhaustion. Subjects wore a placebo or an active nasal dilator strip, in random order, during each test. Measurement of inspiratory elastic work (inew), inspiratory resistive work (inrw), and expiratory resistive work (exrw) was done using an esophageal balloon. Measured variables included VO$\sb2$, V$\rm\sb{E}$, V$\rm\sb{T}$, frequency of breathing (f), inew, inrw, and exrw, (work expressed in joules). There were no significant differences in VO$\sb2$, V$\rm\sb{E}$, V$\rm\sb{T}$ or f between groups ($\rm p>0.05$). No significant difference was found at peak exercise between groups (mean $\pm$ SD; Placebo; inew, $1.1\pm0.6$ J, inrw, $1.4\pm0.8$ J, exrw $2.2\pm1.8$ J; Active; inew, $1.0\pm0.5$ J, inrw, $1.3\pm0.7$ J, exrw, $1.8\pm0.9$ J; $\rm p>0.05$). Wearing an external nasal dilator does not significantly reduce the work of breathing during exercise.

The purpose of this study was to (1) derive gender-specific allometric scaling models using pre-training muscle cross-sectional area (CSA) and body mass (BM) as scaling variables, (2) test model appropriateness using regression diagnostics, and (3) cross-validate the models before and after training. A subset of FAMuSS study data (n = 319, females = 183, males = 136) was randomly split into two groups (A & B). Group A pre-training data for female BM, female CSA, male BM, and male CSA models produced scaling exponents of 1.08, 0.44, 0.63, and 0.68, respectively. The female BM model was deemed inappropriate due to non-normal distribution of residuals. All other models met statistical criteria including normal distribution of residuals. Cross-validation to Group B pre-training data revealed that the models were appropriate, with the possible exception of male CSA model. Twelve weeks of resistance training did not alter the relation between BM, CSA, and muscular strength assessed by allometric scaling.

The purpose of this study was to determine the effect of oxygenated water on endurance exercise performance. Subjects (N=15, VO2max 54.8 +/- 5.8 ml/kg/min) were tested using non-oxygenated water (PL) and oxygenated water (OW). Two maximal exercise tests and 2 submaximal tests were conducted. VO2max (3.28 +/- 0.81 L/min (OW) vs. 3.30 +/- 0.80 L/min (PL)) VE, VO2, or R were not different. Submaximal blood lactate values at 60%, 80% of VO 2max (4.2 +/- 2.1 mMol/L, 6.6 +/- 2.9 mMol/L (OW) vs. 3.8 +/- 1.8 mMol/L, 6.1 +/- 2.4 mMol/L (PL)) and HR (140 +/- 15 bpm, 162 +/- 11 bpm (OW) vs. 138 +/- 15 bpm, 163 +/- 13 bpm (PL)) were not different and neither was time to exhaustion at 90% of VO 2max (5.22 +/- 2.31 min (OW) vs. 6.80 +/- 2.93 min (PL)). Oxygen content of OW (13.1 +/- 1.5 mgO2L-1 ) was higher than PL (6.0 +/- 0.1 mgO2L -1) (p<0.05) but lower than manufacture's claims. Thus, superoxygenated water did not result in any improvements in endurance exercise performance.

The role of airflow limitation (AFL) in exercise-induced arterial hypoxemia (ElAH) was examined in six well-trained competitive cyclists. Two maximal cycle ergometer tests were performed, one while breathing room air (RA; 79% N2, 21% O2) and another breathing a mixture of heliox (He; 79% He, 21% O2) in random order. EIAH was estimated via pulse oximetry of HbSaO2. The results revealed no subject experienced AFL breathing RA or He. Despite a significant increase in V&dot;Emax (RA = 114.3 +/- 27.6 l/min; He = 129.2 +/- 25.5 l/min; p < 0.05) during He condition there was no difference in HbSaO2 during maximal exercise (RA = 95.3 +/- 1%; He = 96.7 +/- 1.5%; p > 0.05). In conclusion, our subject population failed to show any significant decrease in HbSaO2 breathing RA, which makes it difficult to determine if AFL plays a role in EIAH.

Strength increases following short-term bouts of isokinetic training have been demonstrated in the past without regard to limb velocity adaptations. This has been attributed to increased neuromotoric efficiency, rather than peripheral muscular hypertrophy. The purpose of this study was to determine the effects of a short-term isokinetic training regimen on limb velocity. Sixty subjects volunteered to participate and were randomly assigned to one of three groups; control (10 males, 10 females), slow (10 males, 10 females) and fast (10 males, 10 females). Each group was pre-tested by performing five repetitions of concentric/concentric knee extension/flexion movements at 60 and 240 d/s on a Kin-Com isokinetic dynamometer. The slow (60 d/s) and fast (240 d/s) groups then completed two days of training (separated by 48--72 hours) consisting of three sets of eight repetitions while the control group did not train. All groups were post-tested at 7--9 days after the pre-test. Data were collected from the middle three repetitions at 1000 Hz and separated into three velocity ROM phases of acceleration (ACCROM), load range (LR) and deceleration (DCCROM) along with peak force. Four univariate (ACCROM, LR, DCCROM & Force) four-way (2 velocities x 2 genders x 2 times x 3 groups) mixed factorial ANOVA's were performed to analyze the data. Results demonstrated significant decreases in ACCROM and increases in LR between pre and post-tests for the slow group at the slow velocity (ACCROM-1.25 +/- .04 deg vs 1.08 +/- .03 deg; LR-74.80 +/- .11 deg vs 75.35 +/- .09 deg) and for the fast group at the fast velocity (ACCROM-14.24 +/- .33 deg vs 13.59 +/- .29 deg; LR-39.73 +/- .32 deg vs 40.59 +/- .25 deg). Force and DCCROM exhibited no significant differences between testing days for any group. These results collectively point to short-term isokinetic training resulting in velocity specific increased limb velocity. These acute improvements may be explained as the result of neural adaptations, such as increased motor unit recruitment or firing rate, rather than hypertrophic responses due to the relatively short duration of the training stimulus. Furthermore, these accelerative increases produce a more rapid rate of force development which may be important in activities necessitating explosive movement, including sporting events requiring power.