NMES versus No exercise: Beneficial effects?

Hello again everybody! As promised, this week we will be talking about the use of NMES to strengthen normal skeletal muscle without voluntary muscular effort.  Can this in fact be true?  To answer this week’s question, we investigated some literature out there that looks to support the application of NMES for muscle strengthening, more specifically can it provide benefits that outweigh doing no exercise at all?

Laughman and colleagues (1983) used NMES to investigate its effect on Quadriceps Femoris (QF) strength over a 5-week period without superimposed voluntary contractions.  Their parameters were as follows (Table 1);

Frequency:	2500Hz (Russian)
On/Off time:	15s:50s
Times/day:	10
Days/week:	5
Total weeks of treatment:	5
Total Sessions:	25
*All participants were asked to maintain regular daily activites*

Table 1.  Treatment parameters established by Laughman and colleagues (1983).

So what did they find? Essentially, where the control and isometric groups experienced increase in strength gains of 2% (attributed to the evaluation process) and 18 % respectively, the NMES group had a statistically significant 22% gain over the 25 training sessions.  Other significant findings include;

• Patients tolerated progressively increasing amounts of current density, indicating muscle accommodation consistent with strength gains.
• Support for cross-education effect on muscle strengthening via neural effects, which were originally only thought to be possible by voluntary muscle contraction.
• Rapid strength gains in first few weeks with slight plateau achieved in weeks 4 and 5.  Overall, from weeks 1-6, NMES alone had a greater effect that isometric exercise group.
• Patients experienced less joint compression than isometric exercise group, and overall less pain.  Important implications for patients suffering from degenerative joint diseases or post total knee arthroplasty rehabilitation for QF strengthening.

NMES slows the biochemical and histological (Figure 1) changes that accompany disuse muscle atrophy (Figure 2) after major surgery.

Figure 1.  Histological changes within Type I and II QF muscle fibres pre (left) and (post) knee surgery.  

Figure 2.  Disuse Quadriceps muscle atrophy in right (normal) versus left (affected) thigh.

• Important function of NMES to strengthen weak muscle groups or by providing a passive intermittent stretch to shortened joint soft tissue preoperatively.
• Recommended treatment prescription to elicit strength gains in Quadriceps muslces; 10-15min, 1x/day for 5 weeks with frequency and on/off time as described in table 1 above.

Additional Findings;

• Significantly better results in NMES versus no-exercise groups as tested by Bax and colleagues in 2005 (support for NMES for Quadriceps strengthening even 22 years after initial testing).
• Increase in vertical jump height in healthy basketball players (NMES applied to Quadriceps); 4.9cm increase for squat jump, and 0.3cm for countermovement jump (Bax et al., 2005).
• Patient and electrode positioning/size (http://www.medco-athletics.com/lectureseries/neuro.html); no significant differences in-patient with knee in flexion (Snyder-Mackler Approach) versus extension (Fitzgerald Approach).  However, most experts have supported flexion because Quadriceps muscles are placed in a more relaxed/lengthened position therefore allowing for greater muscle range and overall force generation (Fitzgerald et al., 2003).   

So as we can see from the evidence presented, NMES can in fact be an effective modality to increase quads strength in both impaired and normal knee function populations when compared with no exercise and even isometric exercise.  Next week we will be going more in depth with a look at the use of NMES for maximizing quadriceps strength following knee surgery (mainly ACL reconstruction and TKR).  Our main focus will center around two key areas of discussion/comparison;

1.    Volitional exercise versus NMES

2.    Combined volitional and NMES

Hope you all enjoyed this weeks post, SEE YOU NEXT WEEK!!!