Effectiveness of Grounded Sleeping on Recovery After Intensive Eccentric Muscle Loading

Abstract

Purpose: We set out to investigate the effectiveness of grounded sleeping on the time course of recovery with respect to muscle soreness and athletic performance after intensive eccentric muscle loading. Methods: Twenty-two healthy participants were recruited for this study and randomly assigned to an experimental group (GRD, grounded sleeping, n = 12) or control group (UGD, sham-grounded sleeping, n = 10) to evaluate the effects of 10 days recovery with GRD vs. UGD following a single intensive downhill treadmill intervention in a triple-blinded (participant, tester, and data analyst) manner. To operationalize recovery a test battery was performed at baseline and on days 1, 2, 3, 5, 7, and 10 post-intervention: (1) perception of muscle soreness (VAS), (2) creatine kinase blood levels (CK), (3) maximum voluntary isometric contraction (MVIC) for both legs, (4) counter movement jump (CMJ) and drop jump (DJ) performance. Furthermore, in four participants blood was sampled for detailed analysis of complete blood counts and serum-derived inflammation markers. Results: The downhill treadmill running intervention led to distinct changes in all measured parameters related to fatigue. These changes were detectable already 5-min post intervention and were not fully recovered 10 days post intervention. GRD led to less pronounced decrease in performance (CMJ, MVIC) and less increase with respect to CK compared with UGD (all P < 0.05). Detailed blood samples demonstrated that grounded sleeping modulates the recovery process by (a) keeping a constant hemoconcentration, as represented by the number of erythrocytes, and the hemoglobin/hematocrit values; and (b) by the reduction of muscle damage-associated inflammation markers such as, IP-10, MIP-1α, and sP-Selectin. Conclusion: The downhill running protocol is a feasible methodology to produce long term muscle soreness and muscular fatigue. GRD was shown to result in faster recovery and/or less pronounced markers of muscle damage and inflammation. GRD might be seen as a simple methodology to enhance acute and long-term recovery after intensive eccentric exercises.

Keywords: creatine kinase (CK); downhill running; inflammation; muscle soreness; muscle strength.

Figure 1

Schematic illustration of the procedure with a timeline: pretest (–30 min prior to intervention), intervention (downhill running), posttests (+5 min, 24 h, 48 h, 72 h, 5 days, 7 days, and 10 days post intervention) consisting determination of blood creatine kinase content (CK), visual analog scale (VAS) related to muscle soreness, drop jump (DJ) performance, counter movement jump performance (CMJ) and a maximum voluntary isometric contraction (MVIC) of both the left and right leg.

Figure 2

Time course of the % reductions with respect to baseline levels in the counter movement jump (CMJ) across the 10 days post intervention period. UGD, sham-grounded sleeping group; GRD, grounded sleeping group (mean ± SD).

Figure 3

Time course of the % reductions with respect to baseline levels in the isometric maximal strength for the dominant leg across the 10 days post intervention period. UGD, sham-grounded sleeping group; GRD, grounded sleeping group (mean ± SD).

Figure 4

(A) Time course of the % increases with respect to baseline levels for CK-blood levels across the 10 days post intervention period. UGD, sham-grounded sleeping group; GRD, grounded sleeping group (mean ± SD). (B) Individual response analysis for increases in CK levels with respect to GRD (grounded sleeping) and UGD (sham-grounded sleeping). Percent differences are categorized as non-response: <3%, moderate response: 3–10%, large response: 10–20%, and very large response >20%.

Figure 5

Parameters of the differential blood count observed over a defined time, including erythrocytes, hemoglobin, hematocrit, MCV, leucocytes, granulocytes, monocytes and platelets; represented as mean with standard deviation of the defined days of each group; ^nsP > 0.05, ^∗P ≤ 0.05, ^∗∗P ≤ 0.01, ^∗∗∗P ≤ 0.001.

Figure 6

Inflammation markers observed over a defined time, including sICAM-1, IP-10, MIP-1α, MIP-1β, and sP-selectin; represented as mean with standard deviation of the defined days of each group; ^nsP > 0.05, ^∗P ≤ 0.05, ^∗∗P ≤ 0.01, ^∗∗∗P ≤ 0.001.