The Influence of Hip and Knee Joint Angles on Quadriceps Muscle-Tendon Unit Properties during Maximal Voluntary Isometric Contraction.

Determining how the quadriceps femoris musculotendinous unit functions, according to hip and knee joint angles, may help with clinical decisions when prescribing knee extension exercises. We aimed to determine the effect of hip and knee joint angles on structure and neuromuscular functioning of all constituents of the quadriceps femoris and patellar tendon properties. Twenty young males were evaluated in four positions: seated and supine in both 20° and 60° of knee flexion (SIT20, SIT60, SUP20, and SUP60). Peak knee extension torque was determined during maximal voluntary isometric contraction (MVIC). Ultrasound imaging was used at rest and during MVIC to characterize quadriceps femoris muscle and tendon aponeurosis complex stiffness. We found that peak torque and neuromuscular efficiency were higher for SUP60 and SIT60 compared to SUP20 and SIT20 position. We found higher fascicle length and lower pennation angle in positions with the knee flexed at 60°. The tendon aponeurosis complex stiffness, tendon force, stiffness, stress, and Young's modulus seemed greater in more elongated positions (60°) than in shortened positions (20°). In conclusion, clinicians should consider positioning at 60° of knee flexion rather than 20°, regardless if seated or supine, during rehabilitation to load the musculotendinous unit enough to stimulate a cellular response.

Hip and Knee Joint Angles Determine Fatigue Onset during Quadriceps Neuromuscular Electrical Stimulation.

Neuromuscular electrical stimulation (NMES) has been used to increase muscle strength and physical function. However, NMES induces rapid fatigue, limiting its application. To date, the effect of quadriceps femoris (QF) muscle length by knee and hip joint manipulation on NMES-induced contraction fatigability is not clear. We aimed to quantify the effects of different muscle lengths on NMES-induced contraction fatigability, fatigue index, and electromyographic (EMG) activity for QF muscle. QF maximum evoked contraction (QMEC) was applied in a 26 min protocol (10 s on; 120 s off; 12 contractions) in 20 healthy participants (24.0 ± 4.6 years old), over 4 sessions on different days to test different conditions. The tested conditions were as follows: supine with knee flexion of 60° (SUP60), seated with knee flexion of 60° (SIT60), supine with knee flexion of 20° (SUP20), and seated with knee flexion of 20° (SIT20). Contraction fatigability (torque decline assessed by maximal voluntary contraction [MVC] and during NMES), fatigue index (percentage reduction in MVC), and EMG activity (root mean square [RMS] and median frequency) of the superficial QF' constituents were assessed. After NMES, all positions except SUP20 had an absolute reduction in MVC (p < .001). Fatigue index was greater in SIT20 than in SIT60 (p < .001) and SUP20 (p = .01). There was significant torque reduction across the 12 QMEC in SUP60 and SIT60, up to 10.5% (p < .001-.005) and 9.49% (p < .001-.033), respectively. There was no torque reduction during NMES in SUP20 and SIT20. Fatigue was accompanied by an increase in RMS (p = .032) and a decrease in median frequency for SUP60 (p < .001). Median frequency increased only in the SUP20 condition (p = .021). We concluded that QF NMES-induced contraction fatigability is greater when the knee is flexed at 60° compared to 20°. In addition, a supine position promotes earlier fatigue for a 60° knee flexion, but it delays fatigue onset for a 20° knee flexion compared to the seated position. These results provide a rationale for lower limb positioning during NMES, which depends on training objectives, e.g., strengthening or task-specific functionality training.

The Effect of Mat Pilates Training Combined With Aerobic Exercise Versus Mat Pilates Training Alone on Blood Pressure in Women With Hypertension: A Randomized Controlled Trial.

OBJECTIVE: The purpose of this study was to determine the effects of mat Pilates (MP) versus MP plus aerobic exercise (AE) compared with the effects of no intervention on ambulatory blood pressure (BP) in women with hypertension. METHODS: This 3-arm, parallel-group randomized clinical trial assessed 60 women who had hypertension and were 30 to 59 years old. The intervention lasted 16 weeks, and the participants were allocated into 3 groups: MP only (MP group), MP with alternating bouts of AE on a treadmill (MP + AE group), and control group (CG) with no exercises. Primary outcomes were the effects of the interventions on ambulatory BP assessed in the 24-hour, awake, and asleep periods of analysis. RESULTS: A 2-way analysis of variance did not reveal statistically significant differences in between-group comparisons in the 24-hour period of analysis for systolic BP (CG vs MP = 3.3 [95% CI = -7.1 to 13.8]; MP vs MP + AE = 0.7 [95% CI = -4 to 5.4]; CG vs MP + AE = 4.0 [95% CI = -5.2 to 13.4]), diastolic BP (CG vs MP = 2.2 [95% CI = -5.6 to 10.0]; MP vs MP + AE = 1.1 [95% CI = -4.3 to 6.5]; CG vs MP + AE = 3.3 [95% CI = -3.8 to 10.4]), and heart rate (CG vs MP = 3.4 [95% CI = -2 to 8.8]; MP vs MP + AE = 2.0 [95% CI = -3.4 to 7.5]; CG vs MP + AE = 5.4 [95% CI = -0.8 to 11.8]). The awake and asleep periods of analyses also showed similar behavior and did not reveal statistically significant between-group differences. Furthermore, in the responsiveness analysis based on the minimal clinically important difference, no differences were observed between groups. CONCLUSION: The magnitudes of the decrease in systolic BP during the 24-hour period of analysis were -3 and -5.48 mm Hg for the MP and MP + AE groups, without differences for responsiveness between groups. The results suggest that MP supplemented with AE or not may be an alternative adjuvant treatment for women who have hypertension and are using antihypertension medication. IMPACT: Sixteen weeks of MP training reduced ambulatory BP in women who had hypertension. The MP + AE group displayed a BP reduction similar to that of the MP group. A reduction in ambulatory BP can decrease the risk of cardiovascular disease.